BG60746B1 - Method for the preparation of crystalline fructose - Google Patents

Abstract

The process is complex and there are obtained two products of crystalline fructose and a liquid sweetener, for example fructose-rich syrup, from a raw material containing dextrose. A portion of the dextrose isomerized to fructose and the resulting dextrose-fructose-containing solution is fractionated to form a high-fructose solution. The latter is subjected to crystallization to produce fructose, and the residual mother liquor is then mixed with solutions containing dextrose to produce the liquid sweetener.

Description

(54) METHOD OF PREPARATION OF CRYSTAL FRUCTOSIS

Technical field

The invention relates to the preparation of sugars for nutritional purposes, in particular to the preparation of fructose by isomerization of dextrose, and in particular to the simultaneous preparation of anhydrous crystalline fructose and syrup containing fructose and dextrose.

Also of particular importance are the method of crystallization by cooling the fructose solution so as to obtain different degrees of saturation during the various crystal growth periods, as well as the method of producing purified and concentrated fructose syrup.

BACKGROUND OF THE INVENTION

Fructose is a monosaccharide, highly valued as a food sweetener. Fructose is mainly obtained from corn starch and is essentially high fructose corn syrup (HFCS). Syrups, as commercial products, contain from 42 to 90% by weight. fructose to dry matter / dsb /. (As used in the description, including the claims, the designation "dsb" means "dry weight ratio"). The residue is mainly dextrose. The HFCS syrup, commonly used as a substitute for sucrose in soft drinks, contains 55% fructose, 41% dextrose and 4% higher saccharides (all percentages are "dsb"). The dry matter of such a syrup is usually about 77% by weight.

In the production process, the preparation of HFCS begins with the enzymatic degradation of a purified starch suspension. The main source of raw materials is maize starch obtained by wet milling, but starch of similar purity from other sources can also be used.

In the first step of a typical method, the starch suspension is gelatinized by cooking at high temperature. The gelatinized starch is then decomposed and converted into thermostable α-amylase dextrin in a continuous two-step process. The product obtained is soluble dextrin hydrolyzate with dextrose equivalent / DE / 6-15, suitable for conversion to sugars in the next step.

After dissolution and dextrinization, the pH and hydrolysis temperature with DE Е 5 are adjusted for the saccharification step. During saccharification, the hydrolyzate is further hydrolyzed to dextrose under the enzymatic action of glucoamylase. Although the saccharification can be done in portions, in most modern factories the sacrifice is carried out in a continuous process. In the continuous process of saccharification to the hydrolyzate with DE 10-15 after adjusting the appropriate pH and temperature, glucoamylase is added. The carbohydrate composition of ordinary high-dextrose sugar syrup in% is as follows: from 94 to 96 dextrose, 23 maltose, 0.3-0.5 maltotriose 1-2 higher saccharides, all percentages are given relative to dry matter. Typically, the product obtained has from 25 to 37% dry matter. This high-destructose hydrolyzate is then purified to give dextrose-containing feedstock for the subsequent isomerization process.

For the isomerization, it is necessary to obtain a high-quality dextrose feedstock in order for the resulting high-fructose corn syrup (HFCS) to be very poorly colored and to have ash content. High purity of feedstock is also required for efficient use of immobilized isomerase columns.

Enzyme isomerization columns containing immobilized isomerase have been used continuously for several months. During this period, a very large amount of dextrose-containing feedstock passes through the columns, whereby extremely small amounts of contaminants such as ash, metal ions and / or protein contained in the feedstock can accumulate and reduce productivity of the enzyme. Therefore, the dextrose feedstock is purified to a color of 0.1 / CRA x 100 / and to a conductivity of 5-10 μΩ ¹ .

After being treated with charcoal, filtered and deionized, the high-dextrose syrup is evaporated to a suitable isomerization dry matter. In addition, the feedstock is chemically treated by the addition of magnesium ions, which, on the one hand, activate the immobilized isomerase and, on the other, have a competitive inhibitory effect on all calcium ions, which are potent isomerase inhibitors, on the sediment.

The process of isomerization in which some of the dextrose is converted to fructose. is usually carried out in a stream containing from 94 to 96% / dsb / dextrose and from 4 to 6 ° ₀ / dsb / higher saccharides at 40 to 50% dry matter. The flow was pH 7.5 to 8.2 and temperature 25C and subjected to the isomerase enzyme for 1/2 to 4 hours at 55-65C.

The conversion of glucose to fructose is a reversible process with an equilibrium constant of about 1.0 at 60C. Therefore, it can be expected that an equilibrium state will produce about 47-48% fructose, using a feedstock with a dextrose content of 94-96%. However, the isomerization rate near the equilibrium point is so low that it is more prudent to interrupt the isomerization at a conversion wall of about 42% fructose to provide in practice the optimum residence time of the reaction mixture in the reactor .

In a given isocolon / column with immobilized isomerase / the degree of conversion of dextrose (glucose) to fructose is proportional to the enzymatic activity of the immobilized isomerase. This activity decreases approximately exponentially over time. When the column is new and the activity is high, the flow rate of feedstock flowing through the column is relatively low, since a shorter residence time of the source product in the column ensures a fructose conversion rate of 42%. As the time of use of the column increases, the rate of flow of feedstock through the column should be reduced proportionally to provide a longer retention time to compensate for the decreased activity so as to achieve a constant conversion rate. In practice, multiple ozocalons are used in parallel to reduce production fluctuations related to capacity and conversion rate. In such an organization of the production process, each column can operate essentially independently of the others. Differences in the total flow rate of isocolones must be maintained within a relatively narrow range, taking into account evaporation requirements and subsequent finishing operations. In practice, the flow rate cannot be controlled at all times so as to produce a flow of 42% fructose, but this can easily be achieved at an average level.

One of the most critical variables of the method is the pH inside the isocolons. The working pH is usually an acceptable value between the pH value at maximum activity (typically about 8) and the pH value at maximum stability (typically about 7.0 to 7.5). This is compounded by the fact that the feedstock does not have a stable pH at about 60C. Some decomposition processes occur, which release acidic by-products that cause the pH in the isocolon to drop during the process.

Usually the next isomerization step of the production process is the secondary purification of the obtained 42% high fructose syrup (HFCS). During chemical treatment and isomerisation, when the feedstock is held at a higher pH and temperature for a certain period of time, additional coloring of the product is obtained. The product also contains some additional ash from the chemicals added during isomerization. These coloring and contaminants are removed by secondary charcoal treatment and through ion exchange systems. The refined 42% syrup (HFCS) is then usually evaporated to yield 71% of the dry product, which is ready for sale.

The use of activated carbon for the purification of sugar syrups is generally known. U.S. Patent No. 1,979,781 discloses the mixing of raw sugar syrup not mixed with glucose or inert sugar / at 60C Brix (60% dry matter) by 1 to 2% by weight. activated carbon for short periods of time up to 134C. U.S. Patent No. 2,763,580 details the processing of sugar syrups / e.g. of cane, beet or maize / with a dry matter of between 10 and 60%, in particular from 20 to 56% by weight. at 125 to 200C with activated carbon. The patent discloses that partial treatment can be carried out at one concentration and conditions, after which the carbon treatment can be completed at a higher concentration of the solution (obtained by evaporation) or under other conditions.

Many patents relating to the preparation of fructose-containing maize sugar syrups have described, inter alia, treatment with charcoal and subsequent concentration of aqueous solutions having different fructose concentrations (dsb) and different dry matter. U.S. Patent Nos. 3,383,445 and 3,690,948 describe the treatment of syrups containing about 20% (dsb) fructose and with about 40% activated carbon dry matter and subsequent concentration of the syrup / e.g. by evaporation to 7083% dry matter).

U.S. Patent No. 3 684 574 discloses a syrup treatment containing about 20% (dsb) of fructose with a dry matter of about 20% and subsequent concentration of the syrup. U.S. Patent No. 4,395,292 discloses the supply of fructose-dextrose-treated carbon separator columns with a solids content of 10 to 70%, preferably 40%, and subsequent concentration of the fructose-containing extracts. The last patent (4 395 292) describes that extracts containing more than 90% fructose can be obtained, and specifically in Example 7 it is stated that loading a fractionating column with a solution with 40% dry matter produces a fraction containing 100% (dsb) fructose at 9% dry matter.

The resulting syrup (HFCS), after isomerisation, typically contains 42% fructose, 52% unreacted dextrose and about 6% oligosaccharides. For the reasons described above, this product contains practically the maximum amount of fructose that can be obtained in the isomerization process. To obtain a higher concentration of fructose. selective concentration of fructose is required. Many conventional separation methods cannot be used for this purpose since the differences between the two isomers with the same molecular weight are small. However, fructose tends to form complexes with different cations, such as calcium. This property has been used to create manufacturing methods for the separation of isomers.

There are basically two different methods that are used to purify fructose, using resins in a preferred cationic form. One method uses an inorganic resin leading to selective molecular absorption of fructose / see R. J. Jensen. "Method for fractionation of high fructose syrup". Abstracts of the Institute of Engineering Chemistry, 85th National Meeting, Philadelphia, 1978 /.

In the second industrial method, organic resins are used (see K. Venkatasubramanian's article on purification of biomolecules, Eüshpe Engineering, 6: 37-43, 1982). When an aqueous solution of dextrose and fructose is passed through a fractionating column / e.g. 42% high fructose syrup. it fructose is retained by the resin to a greater extent than dextrose. Deionized and deoxygenated oxygen-released water is used as the eluent. Typically, the separation is carried out in a column filled with fine-grained slightly cross-linked polystyrene sulfonate cation exchange resin, preferably its calcium salt. The enriched product, which contains approximately 90% fructose, has been designated as highly fructose corn syrup (HFCS). This VEFCS fraction can be mixed with 42% (HFCS) / starting material / to produce products having a fructose content of between 42 and 90%. The most typical of these products is the 55% fructose syrup, called fructose-enriched corn syrup (EFCS or 55 EFCS). U.S. Patent No. 4,395,292 provides an example (Example 1) for separating a mixture of fructose and dextrose into different fractions and mixing the fructose-enriched fractions to produce 55.8% (dsb) fructose syrup. In the same example, it is described that single fractions with a high concentration of fructose / e.g. 75.1% /, as well as mixed fractions with lower fructose concentration / e.g. 64.5% (dsb) is mixed with 58.2% (dsb / fructose).

The treatment of other purification streams during the rectification process is another important point. Generally, dextrose-rich refined products return to the dextrose feedstock, which feeds the isoclonal system for subsequent conversion of 42% (HFCS) raffinate containing dextrose and fructose and higher fructose content than the feedstock , can be recycled through the distillation column while maintaining high dry matter and reducing the amount of water used. Oligosaccharide-rich raffinate can be recycled into the saccharification system.

The use of water as an elution medium has a great influence on the overall evaporative load of the system. Very low concentrations increase the risk of microbial contamination in the system. Thus, the most important design parameter determined by the economics of the process is to optimize the amount of dry matter at an acceptable frequency and minimize the dilution effect of the eluent. The efficiency of water supply and use must be increased to obtain optimum yield. Yield is important to reduce the cost of re-isomerization.

This is achieved through recycling, improved resin calibration with appropriate redistribution in column filling, and additional multiple entry and exit points in columns. This approach can be used to increase the purity and yield of the product.

In a discontinuous distillation system and the small noticeable increase in the purity of the feedstock that feeds into the distillation columns, that is, a high content of fructose, is reflected in an increase in production by increasing the yields at a certain purity of the product. In practice, this means maximizing the ratio of the volume of feedstock to the volume of the resin over a given cycle, minimizing the ratio of the required water column to the volume of the resin in the cycle, and carefully distributing the fluid in the columns.

Fructose solid phase products

Fructose crystallization methods are known. For example, crystalline fructose can be obtained by the addition of pure alcohol to the syrup obtained by acid hydrolysis of inulin / Bates et al., Natl. Bur. Std. Circ. C 440.1 339, 1942 /. Dextrose fructose production is described in U.S. Patent No. 1 354 664, and U.S. Patent No. 1 729 587 describes the preparation of sucrose fructose by enzymatic conversion.

Fructose forms orthorhombic besfinoidal alcohol-coated strains that decompose at about 103-105C. Hemihydrate and dihydrate crystalline forms of fructose are also known, but it is preferable to avoid the formation of these forms, since in fact they are more hygroscopic than anhydrous forms and have melting points close to room temperature. These properties of the fructose crystalline forms make it very difficult to handle them.

Soluble crystalline fructose (SCF) is obtained by a method in which an organic solvent such as denatured ethyl alcohol is mixed with a high concentration of fructose (95% dsb). This stream crystallizes upon cooling to give pure crystalline fructose. The product was centrifuged to remove from the mother liquor, purified from the solvent and dried.

U.S. Patent No. 4,199,374 describes a method for preparing SCF. Fructose is crystallized from a solution of VEFCS (very fructose enriched with corn syrup) in ethanol. The solution is filled with fine fructose or glucose crystals. The crystals are separated by filtration, centrifugation or other suitable means. The crystals were then washed with alcohol and dried in vacuo. The moisture content of alcohol and syrup in this method should be very carefully controlled to obtain free-floating fine fructose crystals.

It is also possible to obtain a simply dried fructose sweetener (DFS). The method of its preparation consists in drying the fractions obtained with rectification of high fructose content in a rotary dryer, after which they are calibrated through a system of sorting sieves and mills. U.S. Patent No. 4,517,021 discloses the preparation of such granular semi-crystalline solid fructose containing less than 2% by weight. water. The patent states that about 60 wt. of the product is crystalline fructose and less than 35% by weight. of the product is amorphous fructose. A drum dryer is used and the inlet air temperature is 50-80C. Part of the resulting solid fructose product is recycled and serves as the initiator of crystallization.

One of the disadvantages of the DFS method is that the product cannot be called pure fructose, as it is a complex sugar product and does not meet the criteria for "fructose" set by the Food Chemicals Code. Moreover, it is not fully crystalline, which is why it is more hygroscopic and more difficult to handle under conditions of increased humidity than crystalline fructose.

A process with water may also be used to produce crystalline fructose. It usually requires a high fructose feedstock that is cooled to crystallize the fructose from the solution. Such a method has been described in several publications.

US Patent No. 3 513 023 describes a process for the preparation of anhydrous crystalline fructose from an aqueous solution of fructose (minimum 95% dry matter). The pH of the solution should be between 3.5 and 8.0. The fructose solution was concentrated in vacuo to a moisture content of between 2 and 5%. The solution was cooled to 60-85C, sprinkled with crystalline fructose and stirred vigorously while maintaining the temperature within 60-85C. The patent states that, under these conditions, a crystalline mass is obtained which, upon slow cooling, may be cracked or broken and, upon drying, a non-sticky, free-flowing, fine crystalline powder will be obtained. The patent states that this method avoids the formation of a glassy product when this type of fructose solution is concentrated in vacuo and then allowed to cool in the usual way.

U.S. Patent No. 3,883,365 describes crystallization of fructose from an aqueous solution of fructose and glucose with 90% dry matter containing 90-99% / dsb / fructose. The solution is saturated (58-65 ° C). Fructose crystallizes from the solution by adding fructose crystals with a homogeneous solution. The formation of new crystals is minimized by maintaining the crystalline grains that are introduced into the solution at a suitable short distance and keeping the saturation level between 1.1 and 1.2. The volume of the solution increases continuously or in stages as crystallization proceeds. The optimum pH of the fructose solution is stated to be 5.0. and that the crystals thus obtained have the following size between 200-600 μ. The crystals were separated from the solution by centrifugation.

U.S. Patent No. 3,928,062 discloses the preparation of anhydrous crystalline fructose by the crystallization of a solution containing 83-95.5% / dry matter / total sugars and 88-99% fructose. Crystallization can be accomplished by simply cooling the solution at atmospheric pressure or by evaporating the water under reduced pressure. The formation of hemihydrates and dihydrates is avoided by crystallization at a certain fructose concentration and temperature. These parameters are in the saturation region, but below the point at which crystallization of the hemihydrate begins. It is stated there that the mother liquor may be reused to crystallize further quantities of the product, working in the same way without any further treatment. The addition of crystals that serve as the nucleus of crystallization is accomplished by suspending in the solution of pre-prepared crystals.

U.S. Patent No. 4,199,373 describes a process for the preparation of crystalline fructose by introducing 2-15% by weight. crystalline fructose embryos in fructose syrup at a concentration of 88-96% (dsb) and allowing the solution to crystallize at about 10 to 32C at a relative humidity below 70%. The patent states that the crystallization time required is from 2 to 72h. The crystals obtained by this method have the form of large pellets.

U.S. Patent No. 4,144,429 discloses a method and apparatus for producing crystalline embryos. A series of centrifuge separators is used to select seed crystals from germ-treated syrup that have a predetermined size.

Crystallization cooling curves

Cooling of saturated or saturated solutions to crystallize the substance from them is known.

It is also known that the natural cooling of a saturated or saturated solution often results in the embryo being separated, resulting in unwanted large differences in the size of the crystalline product. E.g. in Encyclopedia of Chemical Technology, Volume 7. pp. 243-285 / Kirk-Othmer, John Wiley & Sons. Guy York, Third Edition. 1979), it is stated that, upon natural cooling, a rapid rapid formation of crystallization nuclei occurs in the saturated solution. The article describes that, under controlled cooling conditions, a constant level of saturation can be maintained to achieve controlled seedling formation within certain limits. Figure 5 shows the curves obtained by natural and controlled cooling of the solution published in the article cited above.

SUMMARY OF THE INVENTION

Various aspects of the invention are described in more detail.

I Comprehensive method for teaching fructose-containing sweeteners

In one aspect, the invention relates to the complex preparation of a plurality of fructose-containing sweetening products.

A. Simultaneous preparation of liquid sweetener and crystalline fructose

In one particular embodiment, the invention relates to a method for the preparation of crystalline fructose and a liquid sweetener containing fructose and dextrose, which involves crystallization of fructose from an aqueous solution to obtain a mixture containing crystalline fructose and mother liquor, separating crystalline fructose from the mother liquor alkalis and blending of dextrose with the mother liquor to obtain a liquid phase sweetener containing dextrose and fructose.

In the preparation of crystalline sucrose from an aqueous solution, it is a common practice to reuse the mother liquor for further crystallization, thereby increasing the impurities in the mother liquor, called molasses. This molasses is generally so polluted that it is of value only as an additive to animal feed or as a fermentation medium. U.S. Patent No. 3,928,062 discloses that fructose mother liquor may be reused to produce the next crop of fructose crystals. The relatively low yield of crystalline fructose in one-step crystallization carried out by conventional methods, and the difficulties associated with the isomerization and fractionation of syrups obtained from maize feedstock to obtain fructose feed syrup of sufficient concentration to feed the crystallizer mother liquor for crystallization of fructose again. The combined preparation of crystalline fructose together with a liquid sweetener by the addition of dextrose to the mother liquor allows two high quality sweeteners to be obtained at one time. This, in turn, maximizes the yield of fructose, which is useful as a sweetener and justifies the difficulties associated with isomerization. This process reduces the benefits of fractionation, the main purpose of which is to remove dextrose to provide a starting material for crystallization, while the addition of dextrose to the mother liquor is at the expense of enrichment. achieved in fractionation.

One particular application of this aspect of the invention is a method of producing crystalline fructose and a dextrose-containing and dextrose-containing fructose solution, which consists in isomerizing a portion of dextrose in the feed stream to obtain a first dextrose-containing solution and fructose, separating this solution into the first feed stream and into the second feed stream, fractionating the first feed stream to obtain a high fructose solution. crystallization of fructose from it to obtain a mixture containing crystalline fructose and mother liquor, separating crystalline fructose from the mother liquor and mixing at least a portion of the mother liquor with the second feed stream, to obtain a second solution containing fructose and dextrose, which has a higher fructose content than dextrose compared to the first dextrose and fructose solution. (As used herein, including in the claims, the expression "dextrose and fructose flow means a solution containing dextrose and fructose".

In one related embodiment, the invention also relates to a process for the preparation of crystalline fructose and a liquid sweetener, which consists in crystallizing an aqueous fructose solution to obtain a mixture of crystalline fructose and a mother liquor, separating crystalline fructose from the mother liquor and stopping further crystallization in the mother liquor to obtain a fructose-containing liquid sweetener.

The mother liquor remaining after crystallization is a saturated solution of fructose. It is known from the prior art, e.g. from U.S. Patent No. 3,928,062 that the mother liquor may be reused to crystallize further quantities of crystals. In order to be used for this purpose, it is necessary to heat and concentrate this saturated mother liquor to obtain a suitable, saturated solution of fructose to allow crystallization therein. It has been found that it is better to interrupt the crystallization and use the mother liquor to produce a liquid sweetener than to create conditions that cause crystals to crystallize from it afterwards. As mentioned above, the mother liquor is a saturated solution of fructose. In order to prevent crystallization and precipitation of fructose crystals from this saturated solution during post-treatment, transport and / or storage, steps should be taken to interrupt crystallization in the mother liquor. This aspect of the invention relates to the first embodiment described above, which avoids recrystallization from the mother liquor. This process does not necessarily require the sacrifice of fractionation to be sacrificed, since the inhibition of subsequent crystallization need not be carried out by the addition of dextrose, but may be effected by the ordinary dilution of the mother liquor with water, which stops crystallization without change the purity of fructose in the mother fluid.

B. Multistage fractionation of high fructose sweeteners

One particular embodiment of the invention relates to a method for preparing several fructose-containing sweeteners, at least one of which contains dextrose and fructose, which consists in fractionation of the dextrose and fructose-containing feed stream of dextrose-enriched raffinate, low-fructose extract and high fructose extract in which the fructose concentration is about 90% (dsb), and mixing the low-fructose extract with a composition with a higher dsb dextrose concentration compared to it, to give but a liquid sweetener.

In this context, the term "fructose sweetener" includes any sweetener containing fructose, whether fructose is in solution, dispersed, amorphous or crystalline. For example, a high fructose extract can be used to produce fructose syrup, crystalline fructose or semi-crystalline fructose in which some of the fructose is in a solid amorphous phase.

Fractionation of isomerized dextrose syrup, e.g. one that contains both fructose and dextrose to produce a fructose sweetener is usually carried out by separating the dextrose raffinate and the fructose extract and recycling the residue from the fractionation. For example, U.S. Patent No. 4,395,292 states that such a method is preferred. In the separation of two extracts, one with a higher concentration of fructose (dsb), the so-called high-fructose extract, and the other with a lower concentration (dsb). this higher concentration fructose extract can be obtained without increasing the total degradation of the starting material during isomerisation, as well as any problems related thereto. / Eg reduced fractionation capacity, higher loading than evaporation of the elution water, and / or detrimental decrease in pressure caused by the increased elution water flow required to increase degradation.

The benefit of producing a low-fructose extract is less than that of a high-fructose extract. (This means that it would be difficult to obtain crystalline fructose from the low fructose extract). However, the fructose of this extract can be used to increase the fructose content of sugar syrups obtained from maize that contain even less fructose, e.g. by mixing with isomerization syrup, such as e.g. with 42% fructose syrup to produce high fructose syrup, e.g. 55% fructose syrup.

In a particularly preferred embodiment of this aspect of the invention, the high fructose extract is used to feed the crystallizer to crystallize fructose. Accordingly, in one aspect, the invention relates to a method for the preparation of crystalline fructose and a liquid sweetener containing dextrose and fructose, which comprises the fractionation of a stream containing dextrose and fructose to dextrose-enriched raffinate, low-fructose extract and weight-fructose extract, crystallization from an aqueous solution obtained from the high-fructose extract and mixing the low-fructose extract with a dextrose-containing composition having a dextrose concentration higher than that of the low-fructose extract e preparing a liquid sweetener comprising dextrose and fructose.

This application of the method is of particular advantage because the fructose concentration (dsb) required for crystallization is so high that fractionation of the isomerization flux containing dextrose and fructose to produce a single extract would be impractical. In other words, the rate of decomposition required to produce an extract having a sufficiently high fructose purity to be useful as a feedstock for the crystallizer feed often lowers the fractionation capacity and / or increases the other difficulties involved in fractionation, so such an application is impractical.

A possible disadvantage of the method of taking two extracts - high-fructose and low-fructose, and used separately to produce crystalline sweetener and liquid sweetener, is that the amount of fructose in the non-fructose extract used to increase the fructose content in the isomerized syrup is lower than that of the single fructose extract with the same overall degradation rate. This reduces the total amount of fructose (dsb) in the liquid sweetener. This disadvantage is overcome by the use of a mother liquor from the crystallization of part of the fructose of the high-fructose extract. In other words, in a particularly preferred embodiment of the method, a mother liquor containing fructose, a high-fructose extract and isomerized corn syrup is mixed to produce a liquid sweetener / e.g. 55% fructose syrup.

Variable cooling curve of a saturated solution

In another aspect, the invention relates to a method for producing crystalline fructose from a solution which comprises cooling said solution from the original temperature at an initial cooling rate, then cooling at an intermediate temperature and an intermediate cooling rate that is lower compared to the initial one, and then cooling the solution at a final temperature and a final cooling rate that is higher than the intermediate one.

Figure 5 shows a typical cooling curve obtained during the crystallization process. Curve A is a natural cooling curve and curve B is a controlled cooling curve conducted to achieve a constant level of saturation. Figure 4 shows the cooling curve with different saturation of the solutions according to the invention. When comparing the two figures, one can see the big difference between the cooling curves conducted in the conventional manner and those obtained according to the invention.

The use in the intermediate cooling period of a velocity lower than that in the initial and final periods allows to minimize both the spontaneous formation of crystals in solution and the heat-induced decomposition of fructose, especially during cooling. Reducing the possibility of crystalline germ formation results in a crystalline product of almost the same particle size, and reducing harmful heating increases the yield of crystalline fructose and mother liquor and reduces impurities from degradation products in the mother liquor, thereby improving its usability as a source of fructose to produce a liquid sweetener.

III. Purification of high fructose syrups by low-dry charcoal treatment

In another aspect, the invention relates to a process for the preparation of a concentrated fructose solution, which consists in the preparation of a fructose solution having a concentration greater than about 75% (dsb) by weight and dry matter of less than 40%. treatment of this solution with activated charcoal to obtain a purified fructose solution and evaporation of this solution to a dry matter of more than 40%.

The treatment of activated carbon sugar syrups for purification is known, but it has now been established that a high fructose syrup (dsb) should have a relatively low dry matter to reduce the formation of activated carbon by-products / e.g. . diffructose /, which can reduce the available fructose in the syrup, inhibit its crystallization from the syrup and / or affect the organoleptic properties of the syrup or the sweetener derived from it. Tables 2 and 3 show the effect of dry matter on the formation of diffructose at high fructose concentration in syrup / 95 +% dsb and during contact with activated carbon.

One such embodiment of the invention relates to a process for the preparation of crystalline fructose, which consists in the fractionation of a stream containing dextrose and fructose to obtain a solution with a high fructose content of greater than 90% (dsb), treating this high fructose activated carbon stream to obtain a purified fructose solution, then subject this purified evaporation solution to concentrate and crystallize the fructose from this aqueous solution. This sequence, in which the activated carbon treatment precedes the evaporation of the high-fructose stream, ensures that the treatment is performed on a relatively low dry matter, since high-fructose extracts usually have a low dry matter when obtained by elution on a retention column.

Another specific embodiment of the invention relates to a process for the preparation of crystalline fructose, which consists in crystallizing a solution to form a mixture of crystalline fructose and a mother liquor containing fructose. separating crystalline fructose from the mother liquor, mixing a portion of the fructose from that mother liquor with a liquid containing water to form a low dry matter fructose solution / e.g. less than about 70% /, treating this solution with low dry matter with activated carbon and subjecting the solution to evaporation to obtain a solution of fructose with a higher dry matter.

In one particular preferred embodiment of the process, the mother liquor obtained during crystallization is mixed with a liquid containing water / e.g. tap water, fresh water, saccharide water, such as 42% fructose syrup and the like / to reduce the dry matter before treatment with activated charcoal and then evaporate to obtain a higher dry matter. The resulting solution with a higher dry matter may be used in various ways, e.g. to feed the crystallizer as a high-fructose syrup sweetener or to obtain a feed stream, in all these cases the advantages mentioned above resulting from the reduction of the dry matter of the mother liquor prior to treatment with activated carbon and the subsequent evaporation.

An important feature of the invention is the synergism that results from the simultaneous production of anhydrous crystalline fructose (ACF) and enriched fructose syrup (EFCS). The yield of crystalline fructose from the sugar mass is generally in the range of 40-55%, e.g. 45%. A longer crystallization would increase the yield, but at the expense of a more costly process due to the reduced throughput of the installation. Thus, the significant advantage of the method is that it combines the crystallization of fructose with a process that provides feedstock for it and does not realize losses from non-crystallized fructose.

In some of the prior art methods for the preparation of crystalline fructose, the non-crystallized residues are recycled back to the crystallization process. The problem with this approach is that unwanted by-products such as diffructose, 5- (hydroxymethyl) -2-furfural (HMF) and higher saccharides are accumulated in the recycle stream, while fructose crystallization is essentially selective. As a result, the recycling stream is contaminated with by-products and needs to be purified, which is accompanied by the loss of certain amounts of fructose.

The invention solves the problem of accumulation of by-products by incorporating the liquid phase, which remains after crystallization (mother liquor) in the process of obtaining liquid fructose high sweeteners. In this way, the unwanted by-products are not concentrated at the stage of crystalline fructose production, but are continuously withdrawn from the system. Such a combination eliminates the need for purification of fructose-containing streams and the production of fructose is economically advantageous.

It can be seen in Figure 1 that the preparation of 55% enriched fructose syrup involves a step of separation / fractionation / reaction flow. Generally, fractionation is necessary to produce a syrup with a fructose concentration greater than about 48%. For crystallization purposes, it is preferable for the syrup to have a concentration higher than 95% fructose (dsb). Although crystalline fructose may also be obtained from solutions with lower concentrations, such a method would be economically disadvantageous because of the low yields that would be obtained.

The method of fractionation which is to provide a fructose stream with a concentration of 95% of a feedstock containing 42% (dsb / fructose / the usually obtained product by dextrose isomerization) is known. Thus, it is possible to obtain a feed stream to obtain anhydrous crystalline fructose from fructose enriched corn syrup / EFCS / with slight changes or no change at all in the known method. Preferably, the fractionation system is a chromatographic type, such as a mobile imitation layer, which is well known to those skilled in the art.

Figure 2 shows details of the combined method. As shown in the block entitled "Primary conversion / dilution", the starch was initially converted to dextrose by the enzyme method as described above.

Isomerization

An isomerization process is used to convert dextrose to fructose. The enzyme is fixed on a carrier in a column (called the above isocolon), changing after depletion. An advantage of the invention is that it allows efficient use of the increasing amount of isomerase in isocones. Due to seasonal fluctuations in demand for enriched fructose syrup (55% fructose), a producer who invests in additional amounts of isomerase to meet the period of peak market demand must pay for this increased level of isomerization capacity throughout the year, even when the production of enriched fructose syrup is relatively low. By selectively applying the combined method described herein, the manufacturer can effectively utilize the increased level of isomerization by directing a higher flow of high fructose content from fractionation to obtain enriched fructose syrup when demand for such a product is high and using most of this flow respectively to produce anhydrous crystalline fructose, in case demand for enriched fructose syrup has decreased. In this way, the investment in increased isomerization capabilities of the installation can be used efficiently throughout the year.

Fractionation

Fractionation is carried out in a series or group of resin-containing reactors, which sequentially acts to separate fructose from dextrose into the feed stream. The feed stream and the elution water stream are fed into the reactor system to produce one or more streams of high fructose product, one stream of high dextrose content and / or one or more raffinate stream of high oligosaccharides content . As can be seen in Figure 3, the high dextrose stream is recycled to re-isomerize to fructose, while the high fructose flows are used to produce crystalline fructose or mixed to obtain enriched fructose syrup.

The fractionation capacity is determined by the feed rate, the percentage of fructose in the stream and the utilization of fructose in the stream. For a given fructose content / dsb /. the higher the fractionation capacity, the lower the conversion of fructose required for isomerization. Therefore, in order to reduce the cost of isomerase, it is preferable to operate continuously at maximum fractionation capacity.

In order to obtain a practical yield of a crystalline product in the process of producing anhydrous crystalline fructose, the fractionation product must contain more than about 90% / dsb / fructose, preferably more than 95% fructose. As the product of the fructose syrup preparation process has a fructose content higher than 90% (dsb), special operating conditions must be applied in the conventional fractionation system to reduce the fractionation capacity. These conditions are: reduced feed flow rate without alteration of the elution water ratio to increase solubility and / or increased amount of elution water to increase solubility. These operating conditions have the disadvantage that reducing the throughput of the installation and / or the addition of water requires its subsequent removal, which at least leads to additional energy costs, but this is the preferred alternative.

It is clear to those skilled in the art that when an aqueous solution containing fructose and dextrose passes through suitable chromatographic columns, at least a partial separation of the two substances is obtained. To ensure fractionation, column effluents must be appropriately discharged so that separate fractions are isolated. The various portions that are separated are called fractions. Narrow fractions contain less volumetric volumes of effluent than have been passed through the column compared to "broad fractions". Thus, in view of the purity of the product, the separation can be optimized by appropriately separating the narrower fractions containing the individual substances. Usually, the trade-off made in collecting narrow fractions of wastewater is that the total utilization of the released substances is adversely affected.

It has been found that a flow with fructose content (dsb) above 95%, which is the preferred feedstock for the preparation of crystalline fructose by the process of the invention, can be obtained by separating suitably narrow fractions from the reaction stream exiting the rectification system. the usual method of producing enriched fructose syrup. Such a preferred fractionation system is described in the publicly available U.S. Patent Application to John F. Rasche, No. 861 026, filed Aug. 5, 1986. An apparatus for chromatographic separation of the type imitating a mobile layer. The operating methods described in this publication are suitable for use with this method.

A preferred method of using the aforementioned chromatographic separation apparatus, when used for fractionation, by the method according to the invention involves increasing the eluent-feed ratio from about 1.7 to about 2.0. This feed stream is preferably about 60% dry matter (w / w) and is held at a temperature of about 60C.

The raffinate stream exiting the rectification system is separated into fractions in a manner similar to that used in separating the extraction stream. In this way, the flow, which is relatively rich in oligosaccharides, can be isolated and returned to the saccharification system, subjected to separation, saccharification or withdrawal from the system.

In the absence of purification or recycling of oligosaccharides in the saccharification system, the only way out for the oligosaccharides from the system is the extraction stream, since the usual isomerization does not affect the oligosaccharides. So the oligosaccharides in the refining stream, which are recycled to the isomerization system, simply pass through this system without changing and returning to the feedstock to the fractionation system.

Oligosaccharides are undesirable in the extraction stream since at least part of this stream is used to feed the fructose crystallization process, which is preferably carried out in a solution with a minimum content of other sugars. Similarly, oligosaccharides are undesirable in the liquid sweetener produced by the process according to the invention, therefore only organic amounts of them can be removed from the system by the resulting liquid product.

An additional advantage is the ability to recycle the oligomer-rich stream from the fractionation system into the saccharification system. Such a stream is usually of relatively low dry weight, most commonly about 10%, which means that it contains about 90% by weight. water. The starch suspension obtained in the liquefaction and degradation step to dextrin should be diluted before saccharification. Water from a stream containing oligosaccharides can be used at least in part as a diluent of the slurry, using the water and reducing the evaporation capacity required by the system as a whole.

Mixing

In the conventional methods for the preparation of enriched fructose syrups, the high-fructose fractionation extract is mixed with the isomerization product (typically containing 42-48% / dsb / fructose to obtain the desired fructose content in the final product / 55% dsb EFCS). In the complex process according to the invention, the mother liquor obtained in the centrifugation step after crystallisation contains about 88-92% (dsb) fructose, preferably 90-92%, and the mother liquor with about 83% dry matter is also suitable for mixing. This gives additional possibilities for process changes, as different flows can be mixed - from ion exchange, from coal treatment, which are then concentrated to dry matter 77% as a step in the preparation of enriched fructose syrup. The dashed line in Figure 3 shows some mixing options. Which flows to mix depends, of course, on the mass balance of the system as a whole.

As no chemicals are added to the high fructose stream in the step of producing anhydrous crystalline fructose except for very small amounts of hydrochloric acid and sodium carbonate to adjust the appropriate pH, no appreciable amounts are accumulated in the crystalline fructose production method from new contaminants. Colors, hydroxymethylfurfural and difructose may be obtained during the treatment with charcoal or during the evaporation steps of the crystallizer feedstock. These compounds can be removed by carbon or ion exchange resin treatment to produce enriched fructose syrup.

As more steps of the general process take place in high dry matter, microbial growth is inhibited and has little effect. As a result, the amount of acetaldehyde should not be increased appreciably and, if necessary, may be reduced during ion exchange resin treatment or in the last evaporation steps.

Fructose flow for the mold

PH adjustment

It has been found that the pH of the aqueous fructose solution from which fructose crystals are to be obtained is preferably pH 3.7 and 4.3. although otherwise described in the literature (US Patent No. 3,883,365). Accurate pH control of the crystalline feed stream is required to minimize the formation of diffructose anhydrides. The presence of diffructose anhydrides in the crystallizer has been found to result in lower yields of the crystalline product and adversely affect the size of the fructose crystals formed. It is considered. that the rate of anhydride formation is minimal at pH ranging from 3.7 to 4.3. Both higher and lower pH values than those mentioned herein increase the amount of anhydrides formed. It is also believed that at higher pH values the tendency to form coloring products increases.

Description of the attached figures

Figure 1 represents the various steps of the conventional method of producing 42% high fructose syrup (HFCS) and 55% enriched fructose syrup (EFCS) from starch;

Figure 2 is a combined method of producing two starch-based products, namely crystalline fructose and enriched fructose syrup;

3 is a more detailed implementation of the method illustrated in FIG. 2;

Figure 4 is a graph of the change in temperature of the sugar mass as a function of time after the introduction of the crystalline embryos in the conventional cooling program of the saturated solutions according to the invention;

Figure 5 is a graph of temperature change versus time in a series of crystallizers, with curve A showing the temperature change under natural cooling and curve B with constant saturation cooling.

Examples of carrying out the invention

Example 1.

The effect of pH values on the solubility of fructose and on the accumulation of impurities in syrup with an approximate content of 95% fructose as a dry matter was investigated in the manner described below. The syrups tested are representative for use as feedstock for the crystallization step of the inventive process.

Addition of crystalline fructose to ordinary highly enriched fructose syrup (VEFCS) with a dry matter content of 90% yields a fructose content syrup Table 1.

Fructose /% dsb /

Fructose /% dsb / after hydrolysis Mono-anhydrides /% dsb /

Dry matter / wt. % /

Hmf / ppm dsb /

Acetaldehyde (total ppb / about 95% / dsb). This solution is then treated with granular activated carbon as described above. Thus, the syrup is subjected to the same treatments as the feedstock to feed the crystallizer.

A sample of the syrup described above was treated to adjust the pH to 3.94 and evaporated at 73C to give a higher dry matter. 21 of the concentrated syrup is transferred to a closed flask with a stirrer immersed in a constant temperature bath maintained at about 55C. This support, called the "pH 15 sample", was stirred continuously at a constant bath temperature (approximately 5 m). during which time a second sample is prepared.

The second sample of 95% fructose syrup 20 was treated to pH 5.48 and concentrated at 77C by evaporation. Evaporation is slower than that of the pH 4 sample. 21 of the new sample obtained ("sample pH 25 5.5") is transferred to a closed flask with stirring and the flask is placed in the same constant temperature bath containing the sample pH4.

After adjusting the temperature of 30 baths to 55.5C in both flasks, 50 g of crystalline fructose were introduced. Stirring was continued for 60 h at constant temperature. This is the approximate residence time of the syrup in the OC mold in the process according to the invention.

The resulting sugar mass was separated, centrifuged and the mother liquor analyzed in parallel with samples from the feed 40 syrup. The data obtained from this experiment are summarized in Table 1.

Power supply

Equilibrium

pH 4 pH 5.5. pH 4 pH 5.5 95.81 95.86 95.33 95.24 96.08 96.10 95.33 95.72 0.27 0.24 * 0.48 89.79 89.13 88.90 88.86 5.71 4.03 25.9 6.58 104 48 58 66

Furfural / ppm dsb / Coloring / RBV units / Solubility / g fructose / g water / Saturation * - means 'not found'

Mono-anhydrides were calculated as a difference from the data in the analysis of fructose before and after hydrolysis of the sample. The solubility was calculated from the analysis of fructose before hydrolysis and the dry matter content of the sample. To establish the equilibrium value, some fructose was allowed to crystallize outside the two samples.

The increase in staining in the sample with pH 5.5 is significantly greater than that observed in the sample with pH 4. Stronger staining will result in lower crystallization yield as it requires more mass washing operations. after centrifugation. The need for purification of the mother liquor will also increase.

Both samples show a similar increase in mono anhydrides during feedstock preparation (by comparison, 0.27% dsb at pH 4 with 0.24% dsb at pH 5.5). However, the results of liquid chromatography studies (not shown above) indicate that more diffructose dianhydrides should be obtained at pH 5.5.

Summarizing the result, it can be seen that the sample with pH 4 and less staining shows a decrease in the total acetaldehyde content and has a solubility that does not differ markedly from that of the sample with pH 5.5. The feed syrup for the crystallization process with pH has advantages over the syrup with pH 5.5, since higher yield and better properties of the dummy liquid due to the lower content of coloring agents. The lower pH visibly minimizes staining as well as the formation of diffructose and has little effect on solubility.

As shown in Figure 3, the pH adjustment is conveniently carried out after the fractionation step prior to the charcoal treatment. At this stage of the method, the viscosity of the fructose solution is relatively low and therefore the pH adjustment may

* * 0.29 0.44 4.0 39.6 50.7 163.1 - - 7.64 7.60 - - 1.0 1.0

is carried out relatively easily by mixing the solution with an acid or base. Those skilled in the art will be aware of the acids and bases suitable for this purpose. Hydrochloric acid (HCl) is especially preferred for lowering the pH and anhydrous sodium carbonate (Na ₂ CO ₃ ) for increasing the pH.

Charcoal treatment

The fructose feed stream for the crystallization step has a concentration above 95% (dsb) and it is preferable to treat it with charcoal before concentrating it by evaporation. One of the purposes of charcoal treatment is to remove those impurities that may inhibit crystallization. Another objective is to remove impurities such as coloring agents, CFCs (hydroxymethylfurfural), furfural and acetaldehyde, which adversely affect the properties of the mother liquor and significantly reduce its use as a component of liquid sweeteners. Charcoal treatment is preferably carried out with granular charcoal in an amount of 1-3% dry matter or with powdered charcoal, usually in a smaller amount than when using granular charcoal. The temperature of the syrup is preferably about 7 ° C and typically 15-30, the syrup is preferably about 20 to 25% by weight. dry substance.

It is most appropriate for the charcoal treatment to be carried out immediately after fractionation before evaporation of the syrup. Low-dry charcoal treatment prevents the formation of diffructose in amounts above 0.5%. If the charcoal treatment is carried out after evaporation, fructose losses greater than 2.5% are observed. The temperature of the syrup should be approximately 71 ° C / as determined by comparison with 60C to prevent microbial development in the carbon adsorbent and also to reduce the viscosity of the syrup to achieve good diffusion around the carbon particles. .

Example 2.

Measure the amount of diffructose formed in aqueous solutions with at least 95% (dsb) of fructose content as the dry matter content changes. In the first two experiments, the aqueous solutions were mixed in a flask with 2.7% granular carbon / granular carbon dry matter. Table 2

Time Dry matter / AND /

These data indicate that diffructose is much faster (up to 4 times faster) treated with 50% dry matter than 25% dry solution.

The following four experiments are intended to reproduce the operation of the coal treatment under production conditions in a column at structural flow in a stream so as to allow the measurement of the resulting diffructose in a dynamic flow system, as compared with the results obtained in a static stirring system into a flask.

Two 30.5 cm glass columns in series are used to provide a residence time of the feed stream in the column for about 20 hours. The columns and the short, clean pipe coil used to heat the feed stream are immersed in an adjustable water bath.

To simulate a counter current flow

Table 3 flax by weight of dry matter in aqueous solutions / and stirred at 71C for 24 h. At the zero, sixth, fourteenth, and twenty-fourth hours, samples were taken and dufructose content was measured. The results of the measurements are given in the following Table 2.

Diffructose /% dsb / in:

25% dry in 50 ° _o dry in

0.25 0.47

0.32 0.85

0.38 1.62 0.78 1.94 steady-state charcoal, the columns are initially used until the coal is partially depleted and the second column is then charged with unused fresh granular activated charcoal, placing about 5 cm of fresh charcoal at the point of removal from that column.

This apparatus has been used in four different work options to conduct research, provided that in each of these cases fresh / new / granular charcoal is used. The following options are used:

70% dry matter at 60 ^(C 70% dry substance at 71C 50% dry substance at 71C 25% solids at 71 ° C.

In all embodiments, the process is carried out under continuous feed without recycling for 36 h and the amounts of diffractose present in the effluent at 0, 6, 14, 24 and 36 b are shown in Table 3.

Temperature 60C Dry substance 70% Time h 0 0.32 6 0.83 14 0.26 24 0.39 36 0.24

Diffructose /% dry solid /

7ΓΌ

25% 50% 70% 0.32 0.35 0.32 - - 1.6 0.92 0.95 - 0.61 1.35 1.83 0.64 1.72 2.24

Since at 60C at 70% dry matter, the formation of diffructose is not a problem, as seen in the table, lower temperatures would increase the risk of developing germs and increase the viscosity of the syrup, which is why they should be avoided. In both of the high-dry trials (50% and 70%) at 71C showed levels of diffructose. which increase substantially over time, although the heat and carbon exposure times are the same for all samples. Unwilling to relate to any specific theory, a possible explanation for the formation of diffructose is the catalysis or / and co-catalysis of a substance which is separated from the aqueous solution of carbon and its formation leads to an increase in the conversion of fructose to diffractose during of using carbon.

A carbon filter that traps the finest particles can be used to separate the carbon from the syrup leaving the column with it. Effective filtration is very important as any insoluble substance that passes through the crystallizer would fall after centrifugation into crystalline fructose and directly affect the purity of the product.

Since fructose, which has not crystallized, is mixed to produce a liquid sweetener, treatment with charcoal improves the quality of the liquid product as well. Since the treatment of enriched fructose syrups (EFCS) with charcoal is done towards the end of the process (after mixing), the mother liquor from the centrifugation is purified by two carbon treatments, which enriches the final product.

Evaporation of the starting material for crystallization

The crystallization is caused by the super-saturation of the high-concentration fructose solution, which is obtained by cooling the saturated solution below saturation temperature. The fructose saturation curve (concentration / saturation temperature) is very steep. To achieve a theoretical yield of crystallization within the range of 40-55%, e.g. 40-48%, it is necessary to cool the source feed of the crystallizer fructose syrup to 7-13C, e.g. 8C.

During evaporation, the water is separated from the feed syrup so that the solution is concentrated to a degree that allows the fructose to crystallize upon cooling. Evaporators shall be designed and operated in such a way as to ensure that the solution is concentrated with minimal heat damage to the syrup. A preferred way to effectively evaporate it is to carry it out in two stages. Initially, the output syrup was concentrated in a six-way tube with a vertically downstream evaporator, which had a multiplex effect and mechanical recompression. The fructose stream having a concentration above 95% (dsb) after the charcoal treatment is fed to the evaporator at a dry matter of about 20 to 25% by weight, a temperature of about 88C and a pH of about 3.7 to about 4.3. The syrup thus obtained is about 55 to about 65% by weight. dry substance.

In the second evaporation step, the product obtained in the first step is charged into a plate evaporator with a layer upward movement and a one-time effect that operates at 584.2 to about 609.6 mm Hg. The product of the second step is obtained at a temperature of 74 to about 79C, with a dry matter of 88 to about 90% by weight. Preferably, the second evaporation step is carried out under vacuum at about 660.4mm Hg, so that the temperature of the product is about 60 to 66 < 0 > C, thereby minimizing fructose losses.

The main criterion for selecting and handling the evaporator is to concentrate the solution with minimal heat damage to the syrup. The greatest damage in heating is the conversion of fructose to diffructose, which reduces the yield upon crystallization. The formation of diffractose is favored by the high temperature, high concentration and longer residence time in the evaporator. Since the concentration is completely fixed, the operating conditions of the evaporator must be chosen in such a way as to minimize the temperature and residence time of the syrup in the evaporator.

The suitable evaporators mentioned above are well known to those skilled in the art.

Crystallization

The crystallization can be carried out in periodically operating crystallizers or in continuous ones. In both cases, there are advantages and disadvantages. In the interrupted work process, there is greater flexibility for obtaining crystals of different crystal sizes, and thus the change of crystallization conditions becomes faster and easier. However, intermittent operation has lower productivity since it takes time to charge and evaporate the crystallizer, as well as to import crystalline nuclei. However, it is difficult to ensure uniformity in the size of the crystals in each subsequent batch, and more tanks are needed to store the feedstock and the sugar mass so as to ensure a minimum stay in the mold. Individual cooling systems for each mold are also required. Continuous operation has the opposite advantages and disadvantages, respectively.

Crystallization can be accomplished by single or repeated passage. The first of these ways is preferred. It was found that only 88% of the yield could be obtained for one work cycle, and the crystallization time for the second cycle would be 87% longer. Moreover, the mother liquor in the second cycle is viscous due to the higher level of higher saccharides and the slurry density (the weight of the crystals relative to the total weight of the mass) is lower in the second passage. These two factors reduce the productivity of the centrifuge.

The use of the mother liquor as an additive in the preparation of a liquid sweetener depends largely on its purity. The quality of the mother liquor depends on various factors and measures must be taken to minimize the by-products formed during the crystallization step, with the permissible levels of by-products being limited and, where necessary, their surpluses should be effectively eliminated. Because crystallization is especially selective for fructose, there is a tendency in the mother liquor to accumulate by-products at each subsequent passage through the crystallizer. Thus, this problem is exacerbated in cases of repeated crystallization, and the level of contaminants in the mother liquor often imposes a limit on the number of passes through the crystallizer that can be achieved by the combined method.

Multiple leakage crystallization has been shown to tend to increase the amount of ash, coloring matter as well as hydroxymethylfurfural, furfural and acetaldehyde. Of these, the amount of coloring matter increases most rapidly and, therefore, the usual determinant of the number of passes through the mold that can be efficiently effected is the coloration of the mother liquor.

Suitable measurements to preserve the purity of the mother liquor include careful control of the conditions under which the evaporation, charcoal treatment and crystallization are carried out, and in particular the pH, temperature and duration of the operations. Preferred conditions are discussed in the separate sections of the present specification for the various steps of the method.

The feed syrup for the mold is preferably cooled to about 60C before being introduced into the mold. In order to achieve a yield (theoretical) of 40-48% of crystalline fructose, the solution must contain a minimum of 95% (dsb) of fructose and have a dry matter of 88.589.7% by weight. / nominal 89% / dsb //.

Seed crystals are introduced into the specified portion and thoroughly stirred at about 57 ° C, which is calculated according to the percentages of dry matter and fructose in the portion. After the syrup is well mixed with the imported crystals, a sample is taken to determine the exact saturation temperature. The crystallizer cooling system is adjusted to provide syrup saturation in the range of 1.00-1.05 (relative to fructose concentration). If the sugar mass is already below these limits but no crystallization process is still underway, cooling must continue.

Crystallization is the process by which crystals are formed in liquids, saturated solutions (gels) or saturated vapors (sol). The crystals are charged on insignificant traces of by-products acting as a nucleus. Often, impurities serve to do so. Crystals formed initially in small areas of the maternal phase are then propagated and enlarged. In the process according to the invention, the formation of crystals is thus undesirable since the resulting crystals are of very small size. The size of the crystals is more commonly controlled, preferably using crystal embryos imported into the solution.

The crystallization progress can be indirectly controlled by the value of cooling the sugar mass, keeping the temperature of the cooling water in accordance with a predetermined cooling curve, such that the saturation level is from 1.0 to 1.35, such as e.g. 1.0 of 1.3.

The saturation is preferably determined by direct control of the crystallization development. The saturation can be calculated from the percentage of the dry matter of the mother liquor and the percentage of fructose. Taking into account the saturation data of the solution, it may be decided whether to continue the cooling according to the predetermined cooling curve, or to alter the cooling rate so as to maintain the desired degree of saturation.

An effective crystallization method is preferred, which involves the introduction of crystalline embryos into a syrup with a fructose concentration above 95% dry matter of about 88 to 90% by weight, a pH of about 3.7 to 4.3 and a temperature of about 54 to 59C, with the critical nuclei being about 7 to 10% by weight and have an average particle size of about 150 to 250 mm. After the embryo is introduced, the syrup is subjected to controlled cooling to cause fructose crystallization.

The cooling can be carried out as follows: from a syrup temperature of about 39 to about 46C, the cooling is carried out at a rate of about 0.5C / h; from about 46 to about 30 ”The syrup is cooled at a rate of 1.0 to about 1.5C / h. It is advisable to keep the saturation level below about 1.17 when the syrup temperature is more than about 46C and to keep below about 1.25 if the syrup temperature is below about 46C. The maximum temperature difference between the temperatures of the cooler and the sugar mass is about 10C. Higher temperature differences can cause spontaneous crystallization to occur.

Preferably, however, cooling is controlled at several different degrees over at least three periods. For example, during the first period, when the temperature of the syrup is between about 59C to 52C, the cooling is performed at a rate of between about 1.0 and 1.5C / h and saturation is kept below about 1.20. During the second ("critical") period, when the syrup is at a temperature between about 52 and 43C, cooling is preferably carried out at a rate of about 0.5 to 1.0C / h and the saturation level is kept below about 1.17. And during the third period, the rapid cooling period, the cooling rate, when the syrup temperature is between about 43C and about 30C, is preferably about 1.5 to 2.5C, and the saturation is kept below about 1.25.

It has been found that a preferred way of cooling is to include a continuously operating monitor for saturation level to automatically control the temperature of the cooling water. It is particularly convenient to enter the data from the continuously obtained information from the measurements of the syrup temperature, the temperature of the cooling water and the degree of saturation into the processor. The processor is programmed to use this data to control the temperature of the cooling water and thus the degree of cooling of the syrup. The processor is programmed to first cool the syrup from the seed crystal temperature (Ts) to the predetermined critical temperature (T) at a rate of 2.5C / h. (The critical temperature is calculated from the percentage of fructose and dry matter in the syrup feeder and from the temperature at which the saturation is 1.17). The program provides a cooling rate of the sugar mass of 10 / h at cooling from T 'to 46 and a cooling rate of 1.5 / h at cooling from 46C to the final temperature (most often 30C). However, the program has limitations to prevent the birth of parents. In the first place, the program always ensures that the temperature difference between the sugar mass and the coolant is maintained, so that this difference does not exceed the predetermined values (most often about 14C) throughout the cooling time. Second, the program always ensures that the saturation level does not exceed the predetermined value (typically 1.28) throughout the cooling period. The specific temperatures and values described above can be optimized, and the crystallization dependence curve can be optimized without undue experimentation. The most important factor affecting temperatures is the total dry matter level (% dry matter) and the total surface area into which the seed crystals are deposited. For example, an increase in dry matter would shift the critical period to an earlier stage of the cooling curve and vice versa. Reduction of the total surface on which crystalline embryos are deposited, e.g. reducing them will lead to an extension of the critical period and vice versa.

Crystallization kinetics, saturation

In crystallization kinetics, the rate of growth of crystals is a function of the driving force of concentration - the instantaneous concentration in the mother liquor, depending on the concentration required for the equilibrium state at a given temperature.

Saturation is a measure of the driving force of concentration. There are several ways to determine saturation. Fructose crystallization has shown that the most reliable method for continuous monitoring of the development of processes in a cycle is to determine saturation based on available water. Thus, saturation is defined as the ratio of the amount in grams of fructose in gram of water in the saturated syrup to the ratio corresponding to the equilibrium state.

(Fructose / water) _Existence

Saturation ------------------------ (Fructose / water) _equilibrium

Ideally, the degree of cooling of the batch should be adjusted to control the saturation level of the mother liquor. It has been found that for crystallization of fructose in acceptable yields and with crystalline sizes within the desired limits, the saturation should be from 1.0 to 1.30, the level of saturation below these limits is manifested during the cooling time, while greater saturation from 1.35 causes the formation of embryos to be interrupted.

Formation of embryos

When selecting saturation setpoints, the conditions must be consistent. Fructose does not appear to have detectable unstable zones, e.g. saturation limits at which no embryo formation occurs. The growth of existing crystals is always accompanied by the emergence of new crystals. As the saturation level increases, so does the growth rate of the crystals, but so does the degree of crystal nuclei formation. The purpose is to find a level of saturation to obtain the desired crystal size at an economically advantageous time for the process to take place.

The formation of the crystalline embryos discussed above is either flow or shock. As mentioned, crystallization of fructose is always accompanied by the formation of new crystals. Shock formation of crystals may occur at the beginning of batch formation upon the introduction of crystalline embryos. It is expected to be caused by low temperatures when introduced. If crystallization starts so early, it is preferable to warm the sugar mass to remove the embryos. Once the crystalline embryos have dissolved in the syrup, it can start again.

A preferred method for avoiding the shock of crystals is to keep the saturation level below 1.30 after the crystal embryos have been introduced. Massive crystallization would cause a large increase in the viscosity of the sugar mass, creating many spin difficulties and greatly increasing the purification time. The fine crystals separated from the sugar mass create much greater difficulty in drying and tend to faster agglomeration. Massive crystallization results in a product having an undesirably small average crystal size.

It has been found that a portion of 345.58 I syrup loaded into a 378.5 I volume crystallizer will require a cooling cycle of 30 to 80 hours, typically about 35 to 40 hours, for crystallization of fructose. During this period, the syrup is usually cooled in several stages, preferably in three stages at different cooling rates. The requirement for different cooling rates in the different steps is due to the nonlinear dependence of the crystallization of fructose on temperature. The different velocities correspond to the different crystal growth periods created during cooling.

Initial cooling covers temperatures below about 49C. The planned cooling rate is about 1 to 4C / h; the normal speed is 2C / h, which requires 4 to 6 hours to perform at this stage, preferably about 8 hours. During this time, only the introduced germ crystals increased almost exclusively, and the density of the sugar mass increased slowly. Most of the heat load of the cooling water comes from heat removal.

The formation of crystalline embryos may occur at this stage, however, only if the embryonic temperature of the embryos is too low or the saturation exceeds 1.3.

During the critical period, the rate of increase increases by a factor of 2 to 4. The density of the mass increases rapidly and the new crystals that appear are increased to the desired size. Both competing processes of crystal growth and nucleation are accelerated.

The boundaries of this area are not clearly defined. The best place is at a temperature of 49 to 43C. Caution is needed in this area as the process of crystal formation can be accelerated and out of control. While maintaining a moderate level of saturation (from 1.05 to 1.20), it has been found that the formation of crystalline nuclei can be kept within acceptable limits. Low cooling speed is the preferred way to control the degree of saturation. The cooling rate in this zone is about 0.5 to 3.0C / h, and a cooling rate of 0.5 to 1.5C / h is usually recommended. The estimated time for the "critical period" at this speed is about 10 to 40 hours, preferably 1822 hours.

In some cases, high levels of saturation may not cause the formation of crystalline embryos. In such cases, further cooling may result in the formation of fructose hemihydrate. This type has needle-like crystals that cause a very high mass viscosity (> 800,000 cps). It is not practical to spin this suspension. It can even overwhelm the mold. Hemihydrate crystals can be detected during routine product inspection and completely removed during the cooling period.

After the "critical period" is over, the mass density is high enough to provide a higher cooling rate without the formation of crystalline nuclei. In this rapid cooling zone, the temperature of the cooling water can be lowered rapidly. The rate of cooling of the sugar mass is about 1 to 7C / h, and a speed of 1 to 4C / h is usually recommended. Cooling from 43C to a final temperature of about 3824C takes about 3 to 12 hours, typically 8 to 12 hours. Rapid cooling without crystalline nucleation may take place, but then the process of crystal growth will slow down and the batch will remain at a higher saturation level at the end of the process. Part of the residual saturation can be reduced by moving the sugar mass into a mixer or mixing tank over a period of time.

Since cooling can be performed faster in the "fast cooling period" than at an earlier stage of the process, it has a certain limit on how large the temperature difference between the cooling water and the sugar mass can be. This difference is not precisely determined, but cooling does not require a temperature difference between the sugar mass and the cooling surface greater than about 15C / h. A temperature difference greater than that indicated may cause the formation of crystalline nuclei and contamination of the cooling surface.

Introduction of crystal embryos

The temperature of introduction of the crystalline embryos may differ from the saturation temperature of the mother liquor in the feedstock filled crystallizer. In order to obtain this information, a liquid chromatography of the feed syrup can be performed and the refractive index measured. These data are used to calculate the fructose concentration, the percentage of fructose and the dry matter in the feed syrup. The introduction of crystalline embryos may occur at a saturation of greater than 0.96, eg from 1.0 to 1.10.

Preferably, the imported crystalline fructose has an average crystalline size of about 100-400 μ. It is recommended that the amount of crystals imported is from 1 to 20% (dsb). This amount is determined by the desired size of the crystals in the final product. The crystalline embryos are introduced into the catalyst feedstock, making every effort to evenly distribute the imported crystals into the crystallizer. As mentioned above, U.S. Patent No. 4,146,429 discloses a method and apparatus for producing crystalline embryos.

The crystallization is preferably carried out by first mixing the crystal germs with the sugar fructose syrup to form a suspension for introduction into the crystallizer. This has the effect of conditioning the surface of the crystalline embryos. Such pre-introduction of crystalline embryos into the syrup minimizes the formation of blisters in the crystallizer due to the introduction of crystalline embryos. Bubbles are the points where unwanted crystallization can start.

Continuous introduction of crystalline embryos is of great importance in providing the surface area for the growth of fructose crystals. Since the surface / volume ratio of the germ crystals generally decreases with increasing particle size, if the size of the germ crystals is larger, the germ crystals need more weight to obtain the desired surface.

In another case, a portion of 5 to 30%, preferably about 10 to 20%, of the product may be left in the crystallizer to be used to initiate crystallization. This procedure is much easier to perform than using dry crystalline embryos, but it results in more irregularity in crystal size, since the residue used to provide crystalline embryos contains fine particles that would otherwise have been removed in the spinning and drying stages. In this way, a product with a more variable crystal size is obtained, which can then be saturated to provide the standard crystal sizes of the final product.

A preferred way is to add hot syrup to the residue which will raise the sugar mass to a saturation temperature / approximately 56C while the feed syrup is cooled to the crystalline embryo loading temperature. Part of the crystalline mass is probably lost in this process. Despite this fact, the final mass density is preferably from 2 to 10% (dsb). The critical part of this operation is determined by the final temperature reached by the feed syrup and the sugar mass, which will provide a saturation of 1.00 to 1.10, whereby the loss will be minimized and the germ production will be small.

Example 3.

Fructose crystallization was carried out on a pilot plant using a conventional crystallizer using a feed syrup with a fructose content of 95.82% (dsb) at 89.60% dry matter. The crystallizer is provided with a central shaft stirrer. Cooling is carried out by internal fins attached to the central shaft. The crystallizer is almost filled with 386.1 l syrup. Cooling is carried out for about 40 hours after the crystal embryos have been introduced. At the end of the period, significant glut remains /1.17/. The cycle is controlled by tracking the change in saturation. The crystal embryos are obtained by sieving the crystalline product through a 2A Fitzmill sieve. The material is sieved through a 55 and 100 mesh screen so that it has an average particle size of 161 μ. The dry crystalline embryos were added directly to the syrup in the mold. Table 4 shows the effect of Table 4 on the cooling program used during crystallization. The saturation was increased in the first 18 hours to a maximum of 1.26. It then drops to about 1.17 and remains so during cooling.

Starting period embryonic start / C / h / temp

2.0 - 10,857

10.8 - 20.85G'S

20.8 - 30.844C

30.8 - 40.838C

Extreme Speed of temp cooling 5GS 1.25 44C 0.98 38C 1.11 30C 1.46

The crystals in the resulting product have an average size of 268 μ. The yield of the crystalline product is 46% of the fructose content of the syrup.

Separation

A preferred method of separating fructose crystals from the mother liquor is centrifugation in a basket centrifuge. It was found that in a 14 x 6 ”centrifuge, 13.14 1 sugar mass could be separated in about 10-15 minutes. This period includes only one to three washes, preferably two, with warm water (49-93C). Higher flushing water temperatures can cause greater dissolution of fructose and loss of yield. It is recommended that the amount of washing water be from 1 to 5% by weight of the sugar mass. Deionized water may be used. The pH of the wash water is preferably in the range of about 3 to 5.

Preferred operating conditions for the centrifuge used to separate fructose crystals from the mother liquor are the following: gravity about 1400, precipitate thickness from about 5 to 7.5 cm, precipitate moisture between about 0.7 to 1.5% water, product purity about 99.5%, preferably above about 99.8%. The sludge moisture and its purity are important factors for obtaining a non-agglomerating stable product.

The product was washed in the centrifuge before being removed. It is preferred to rinse with water at a temperature between about 65 and 82C in an amount of about 1 to 1.5% by weight. relative to the sugar precipitate. When used in this way, the product losses from flushing are usually about 5 to 10%. The fructose-containing wash water can be recycled at the coal treatment stage to remove impurities and then concentrated.

Drying

Different types of dryers can be used to dry the resulting product. Fluid-bed dryers with vibrating fluid bed, shelf and drum dryers are suitable. Preferably, the wet centrifuge sludge is metered into a continuously operated mixer by means of a screw conveyor at different speeds. The dry recycled material is dispensed in a closed conveyor (to avoid mixing with the air) at a nominal ratio of up to 4: 1 to the wet sludge. The treatment in the mixer must be sufficient to allow the wet material to be mixed with the dry material. The mixed precipitate was then transferred to the oven.

It is preferably dried simultaneously to avoid overheating of the product. The room air must be pre-purified by passing through an ultrafine borosilicate filter designed to remove 95% of the particles with a size of 0.5 μ. The air is then heated to a temperature so that, after mixing with the air from the cooler, it reaches 71C, at which time it is introduced into the dryer.

The product leaves the oven at about 54C and is transported to the cooler. A controlled amount of the product is recycled without cooling to be introduced into the dryer to treat the wet sludge from the centrifuge. The most critical indicator of a drying operation is the humidity of the incoming sludge. If the humidity is too high, pellets and agglomerates are produced upon drying. Humidity can be adjusted by the amount of dry crystals that return to the wet precipitate. Although a 2: 1 ratio of dry recyclable product to wet sludge is generally sufficient to obtain well-formed crystals to ensure good spin and avoid agglomeration, a ratio of 3: 1 is required.

The spinning precipitate is preferably dried in a rotary dryer to reduce the moisture content of the fructose crystals to about 0.1% by weight. It was found that if the centrifugation sludge moisture was above approximately 1.5% by weight. lumps of product will form in the dryer. As indicated, the humidity of the spinning precipitate was adjusted by adding a dry product. It is advisable not to allow the temperature of the product to exceed 60 ° C. Preferred operating conditions for the dryer are as follows: inlet air temperature of about 76 to 121C, preferably 76 to 93C, outlet air temperature of about 54 to 63C, product temperature of about 52 to 57C, and moisture content of the product below about 0.1%, preferably lower than about 0.07%.

Conditioning

It has been found that if fructose crystals are stored too warm, lumps will form during the stay. This phenomenon is also observed in the preparation of dextrose and sucrose. As the exact mechanism has not been studied, it is assumed that moisture migrates from the larger crystals to the smaller crystals and causes further crystallization of the boundary surface. This process is the result of either a temperature difference or a difference in humidity, both of which are due to the fact that the crystals are not in equilibrium. Tests show that when the product is dried to a lower value (about 0.05%) and cooled to room temperature, a free-flowing product without lumps is obtained. In order to be in equilibrium with fruit crystals with a humidity of 0.05%, the air at 70C must have a relative humidity below 50%.

For these purposes it is appropriate to use a rotary counter with a counter-flow of air. For cooling the crystalline product to temperatures below about 24C. preferably under 22C cooled dry air is used. It is recommended that the inlet cooling air be at a temperature below about 21C and relative humidity below about 40%. The residence time in the cooler must be sufficient to ensure good product conditioning. The moisture content of the final product is preferably lower than about 0.07%.

The final product can be calibrated by sieving and / or grinding. Continuous storage at high temperature causes the product to shrink and stain, even if it is placed in moisture-proof bags. Storage must be under conditions of controlled humidity.

Mixing

The mother liquor separated from the crystalline product by centrifugation may be returned to the production cycle to obtain enriched fructose syrup (EFCS).

In addition to being able to be mixed with dextrose, the mother liquor that remains after crystals are separated can simply be diluted with water to give a very enriched fructose syrup (VEFCS).

After separation of crystalline fructose, the mother liquor may be mixed with dextrose or with a dextrose-containing solution to obtain as a final product a liquid sweetener containing dextrose and fructose, e.g., 55% EFCS. As shown in Figure 3, some of the dextrose-containing streams can be mixed with the mother liquor before being fed to the last finishing operations. The selection of the individual streams or only one of them is determined by the state of mass balance, the aim being to obtain the desired fructose content of the liquid sweetener as a final product. Most often, by carrying out the combined method according to the invention, a liquid product containing 55% / dsb / fructose is obtained. If there is sufficient fructose in the mother liquor, it is even possible to mix with it the dextrose flow of saccharification, which usually contains 94-96% / dsb / dextrose.

Conversely, if the mother liquor contains 90-92% fructose, it can simply be diluted with water to obtain a liquid sweetener. Such dilution is recommended if it is desirable to retain fructose as a liquid, since further crystallization of fructose from the mother liquor is possible, provided that it is not diluted below the saturation point at all possible temperatures at which it can to fall. In addition to dilution water, the following diluents are suitable: aqueous sugar syrups such as dextrose syrups, high fructose syrup HFCS, very fructose enriched syrup / VEFCS / or enriched fructose syrup / EFCS /, and production streams of such syrups. Another way to prevent crystallization of fructose in the individual mother liquor is to take measures to prevent the solution from evaporating the water in it or to reduce the amount of evaporating water, as well as to add substances that inhibit crystallization.

Another use of the separated mother liquor or portions thereof is to obtain a non-crystalline or semi-crystalline fructose sweetener. This is accomplished by dispersing the mother liquor on a nutritious carrier and drying the dispersion to obtain a fructose-containing sweetener, where the fructose is in amorphous or semi-crystalline form. The preferred carriers on which the liquid is dispersed are fructose crystals.

U.S. Patent No. 4,517,021 describes a process for preparing a semi-crystalline fructose composition. The methods described therein may also be used by the method according to the invention. The separated mother liquor according to the invention can be used as a fructose syrup to carry out the process and the resulting crystalline fructose can be used as an initiator of crystallization. In this way, a combined process for the preparation of crystalline fructose, semi-crystalline fructose and one or more fructose-containing liquid sweeteners has been devised.

The above examples describe specific embodiments of the invention. It will be apparent to those skilled in the art that many modifications and modifications to the devices, compositions and methods are possible without departing from the scope and meaning of the invention. These modifications are also included within the scope of the claims.

Claims (11)

Patent Claims A method for the preparation of crystalline fructose and liquid sweetener, fructose and dextrose, characterized in that it involves crystallization of fructose from an aqueous solution and the addition of dextrose to the solution after removal of fructose. A method according to claim 1, characterized in that the aqueous solution containing fructose and dextrose is separated into two streams, the first of which is fractionated to obtain a high content of fructose and after crystallization and separation of the fructose part thereof. combines with the second stream. A method according to claim 2, characterized in that the aqueous solution containing fructose is subjected to an isomerization treatment of a portion of the dextrose therein, to obtain an aqueous solution containing fructose and dextrose. The method according to claim 1 to 3, characterized in that the crystallization of the fructose is carried out at a pH of 3.7 to 4.3. 5. The method according to claims 1 to 4, characterized in that before the crystallization the aqueous solution containing fructose is treated with charcoal and then a portion of the solvent is evaporated. 6. The method according to claims 1 to 5, characterized in that the aqueous solution containing fructose and dextrose is fractionated to obtain a solution enriched in dextrose, a first fructose solution and a second fructose solution, the second fructose solution having higher fructose content than the first, and fructose crystallizes from the second solution or from the solutions obtained therefrom, and the solution, after removal of fructose, is added to the first fructose solution and to an aqueous solution containing dextrose with a higher concentration ation as dry matter relative to the first solution. A method according to claim 6, characterized in that the solution containing fructose and dextrose is separated into a first and a second stream, the first stream being subjected to the fractionation and crystallization of fructose, and the second is added to the first fructose solution and to the solution remaining after removal of fructose. as an aqueous solution containing dextrose. A process for the preparation of crystalline fructose and a fructose-containing liquid sweetener, characterized in that the aqueous fructose solution is crystallized to form a mixture comprising crystalline fructose and a mother liquor; crystalline fructose is separated from the mother liquor, in which further crystallization is inhibited to obtain a fructose-containing liquid sweetener. 9. A method for producing crystalline fructose, characterized in that a dextrose and fructose-containing stream is fractionated to produce a high-fructose stream with a fructose content greater than 90% of the dry matter to be treated. Application: 5 charcoal figures to obtain purified fructose flow and evaporate to give a more concentrated fructose solution from which fructose crystallizes. 10. A method for the preparation of crystalline fructose, characterized in that the solution of fructose is crystallized to form a mixture of crystalline fructose. 10 fructose and mother liquor containing fructose. crystalline fructose is separated from the mother liquor, at least part of which is mixed with an aqueous solution to give a solution of fructose with a lower dry matter, which after evaporation with activated charcoal is evaporated to give a fructose syrup with a higher dry matter . A method according to claim 10, characterized in that the cooling of 20 solutions in the original temperature range are carried out at an initial cooling rate, then the cooling in the intermediate range is at an intermediate rate that is less than the original cooling rate, the solution in the final temperature range is carried out at a speed, which is greater than the rate at the intermediate cooling stage. Publication of the Patent Office of the Republic of Bulgaria 1113 Sofia, 52-B Dr. GM Dimitrov Blvd.