WO2008068572A2

WO2008068572A2 - Process for recovery and production of carbohydrates from jerusalem artichoke tubers

Info

Publication number: WO2008068572A2
Application number: PCT/IB2007/003686
Authority: WO
Inventors: Vladimir Golubev
Original assignee: Melita Financial Group
Priority date: 2006-12-04
Filing date: 2007-11-29
Publication date: 2008-06-12
Also published as: ITTO20060860A1; WO2008068572A3

Abstract

An integrated method for the global recovery and production of carbohydrates, in particular inulin, pectin, fructose-glucose syrup and vegetable fibre from Jerusalem artichoke tubers, in which the crushed tubers are subjected to extraction in water in a cavitation extractor, including the phases of : a) subjecting the crushed tubers to extraction in water with a volume ratio from 1:3 to 1:8, with a cavitation index from 0.05 to 0.1 for times from 10 to 15 minutes, to provide the extraction in liquid phase of the carbohydrate fraction containing mainly inulin; b) separation of the liquid phase containing inulin from the solid phase through filtration; and c) purification and concentration of the aqueous filtrate containing inulin; for the production of pectin the Jerusalem artichoke tuber pulp, separated from the filtrate in phase b) is subjected to extraction in a rotary cavitation extractor from 2.1 to 2.5, for a time from 45 to 300 seconds; preferably, a portion of the aqueous concentrate containing inulin, produced in phase c), is subjected to hydrolysis with citric acid to provide a fructose-glucose syrup.

Description

Process for recovery and production of carbohydrates from Jerusalem artichoke tubers

*** The present invention is an integrated method for the recovery of carbohydrates from Jerusalem artichoke tubers, particularly for the production of inulin, pectin, fructose-glucose syrup and dietary fibre.

These products find uses in the food, pharmaceutical and medical industries, and also as food-grade final products.

The Jerusalem artichoke {Helianthus tuberosus L. , is a plant native to North America, cultivated for its tuber, which is used as a root-vegetable food product. Unlike other tubers, but a characteristic common to other plants belonging to the Asteraceae family, Jerusalem artichoke tubers have the characteristic of storing fructo-oligosaccharides, particularly inulin.

Thanks to the high content of inulin, as well as that of pectin and food-grade dietary fibre, Jerusalem artichoke is employed in the treatment of metabolic diseases, type I _, and type II diabetes mellitus, as well as in the treatment of gastrointestinal diseases, cardiovascular and immunodeficiency disorders. The simplest traditional mode of use of Jerusalem artichoke tubers is directly as food; however this use is limited, from a practical point of view, by major problems due to the need for specific storing conditions in order to avoid the development of a bitter taste.

Therefore, from an economic point of view, the use of Jerusalem artichoke tubers as the source for the extraction of dietary carbohydrates, particularly inulin and pectin, whose market value is considerably higher than that of the raw material in which they are contained, is desirable and convenient.

FR-A-2 502 909 describes a continuous method, in which the Jerusalem artichokes are washed, crushed and pressed to extract the juice. A disadvantage of this method consists of the fact that it provides only one product, that is, a fructose-glucose syrup, which is dark in colour and has a characteristic odour.

The Russian Federation patent RU 2 066 965 describes a method for the production of inulin, in which Jerusalem artichoke tubers are crushed, mixed with water and subjected to cavitation at the temperature of 35⁰C - 40⁰C for 15 - 65 minutes, with a cavitation index between 0.15 and 0.35, after which the juice is separated and subjected to ultrafiltration with hollow-fibre filters.

The filtrate is purified on an ion-exchange column until the percent inulin content is 20% - 21%, after which the product obtained is subjected to drying. This method is limited to the production of inulin alone, with an inulin yield that is not more than 65%.

The Russian Federation patent RU 2 066 962 describes a method for the production of pectins from vegetable products that contain it by hydrolysis and extraction through cavitation in a hydroacoustic cavtation extractor; the hydrolysis/extraction are performed with cavitation indices of 0.9 - 1.9; the solid phase is separated from the liquid one by centrifugation and the liquid phase is subjected to microfiltration until the percent pectin content in the liquid phase reaches approximately 3.8%. The pectinaceous extract is then concentrated further up to a percent content of approximately 8%, by vacuum purification, followed by a drying step at a temperature of 75°C - 92°C. This method is penalised, from an economical point of view, by the fact that it provides pectin alone, with a yield of no more than 60%.

The Russian Federation patent 2 224 026 describes a method for the production of a fructose-glucose syrup that includes the phases of tuber preparation for processing, scalding, crushing, and pressing of the juice. The fructose-glucose syrup is obtained through acid hydrolysis of inulin with orthophosphoric acid for 30 - 120 minutes, with a pH of the solution between 0.5 - 5.0 and a temperature between 35°C and 100⁰C.

The hydrosylate is then neutralised with lime milk and the insoluble calcium phosphate deposit removed by centrifugation. The neutralised hydrosylate is purified by membrane ultrafiltration. The obtained filtrate is then subjected to purification by ionic exchange and the purified fructose and glucose solution is subjected to evaporation at a maximum temperature of 80⁰C to provide the syrup.

Also this method is directed at providing only fructose and glucose syrup and reaches a low final product yield (60% maximum) .

In addition, another method for processing Jerusalem artichoke tubers is known, which includes the primary preparation, crushing, separation of pressed juice from the solids, acid hydrolysis of the inulin in the separated juice, the purification of the juice with activated carbon, its clarification and concentration for the production of the fructose-glucose syrup (see V. N. Golubev, E. V. Volkova, K. M. Kuscialkov: Jerusalem artichoke, composition, properties, method of processing, fields of application, Moscow 1995, pg . 52) .

The imperfections of this method concern major inulin losses (more than 30%), as well as the impossibility of performing multiple processing of the Jerusalem artichoke tubers to obtain inulin, pectin, fructose-glucose syrup and food-grade fibre. Since the extraction of inulin is performed with high cavitation indices, part of the pectins are subjected to degradation, which causes a considerable reduction in the yield of pectins .

The Russian Federation patent RU 2 218 061 describes a method for the processing of Jerusalem artichoke tubers, which includes the phases of crushing of the tubers, electroplasmolysis of the crushed mass, its separation into juice and solids by pressing. After these phases, the acid hydrolysis of the juice, the purification with activated carbon, the clarification with lime milk, the centrifugation, the separation of the juice and concentration to a dry-matter content equal to 50% are performed. The solids and the food- grade fibre provided following pressing are subjected to drying at a temperature of 55°C - 65°C until a humidity of 6% - 14% is reached, after which they are ground to a powder.

This processing method has low efficiency in the global processing of the tubers from an economical point of view, since only a fructose-glucose syrup and dietary fibre are provided, as well as having a low yield of syrup (60% maximum) .

The object of the present invention is that of providing a perfected method that provides also an improvement of the qualitative characteristics of the above-mentioned carbohydrates . In view of these objectives, the object of the^' invention is a method as defined in the attached claims .

In particular, the method according to the invention is based on the identification of specific conditions for the extraction of inulin and pectin that allow the optimisation of production yields.

Further characteristics and advantages of the method according to the invention will be evident from the detailed description that follows. In the attached drawings, figure 1 is a schematic view, provided as a non-limiting example of a rotary extractor-cavitation disintegration device, usable in the field of the invention. a) Preparation of the tubers, washing and crushing The first phase of the method according to the invention consists of preparation of the Jerusalem artichoke tubers; fresh, chilled or frozen tubers are used, which are subjected to washing with clean running water, then inspected and washed at least a second time; it is preferable to perform three washings.

The method does not include thermal pre-treatment by scalding, for example a steam-treatment of the tubers nor a peeling operation, since it has been determined that these operations lead to a substantial reduction in the quantities of inulin, pectin and fructose-glucose syrup, because the greater part of such components are found in the peel and in the thin layer under the peel, and also a 5%-10% loss of the raw material with a substantial reduction in the overall economic yield of the production. Therefore it is preferable to perform a triple washing of the tubers in water.

Following the washing, mechanical cutting of the tubers into sections, cubes or shavings is performed. The crushing dimension is typically included between 3 mm and 8 mm.

Preferable, the crushed tubers are then subjected to spraying with a citric acid solution (typically 5% citric acid) to prevent their blackening caused by non- fermentative oxidative processes. The crushed material is then sent to a collector provided with a valve that 'protects it from contact with air, and it is then sent through a screw transporter to a volumetric doser on the inulin production line. From the volumetric doser, the determined quantity of crushed Jerusalem artichokes is sent to a container, in which it is mixed with a dosed quantity of water,

^■ preferably demineralised, heated up to the temperature, preferably, of 65°C - 80⁰C. Preferably, the previously crushed material is mixed with demineralised water at a proportion between 1 : 3 and 1:8 in volume . b) Extraction of inulin

The inulin extraction operation is performed in a rotary cavitation extractor, preferably at a temperature between 75°C and 80⁰C, and with a cavitation index between 0.05 and 0.1 for 10 - 15 minutes .

Fig. 1 illustrates a schematic view of a rotary cavitation extractor usable in the field of the invention. Said rotary cavitation extractor disintegration device, indicated in its entirety as 1, includes a stator in the form of a stainless steel cylinder provided with a plurality (typically four) of deflectors 2. The raw material dispersed in water is fed through an inlet connector 3, with the help of a screw pump for viscous fluids 4. A rotary cavitation device is placed inside the stator chamber, mounted on a shaft driven by an electric motor 6 connected to a gear reducer 7.

The rotor is formed by two apposed hollow stainless steel semi-spheres; on the extreme outer border of the two rotating surfaces of the rotor there is a number (preferably odd) of sharp teeth. In addition, on the lateral surfaces of the semi-spheres of the rotor .a quantity (preferably an odd-number) of trapezoidal holes with rounded edges are provided.

Pressure regulation is accomplished through a regulation valve 8, placed on the recycling conduit connecting the outlet fittings 9 of the rotary extractor to the feeding tank 10.

In the method according to the invention, inulin extraction is performed with a cavitation index between 0.05 and 0.1. The cavitation index is defined as the ratio between the volume of the cavitation bubbles and the volume of the liquid in the cavitation chamber and this parameter can be easily defined on conventional cavitation extractors by the expert in the field.

The extraction method can be performed in a plurality of extractors placed in parallel.

Control of the quantitative output of inulin is provided through an instrumental method, in particular through a refractometric method performed continuously, c) Production of inulin Following the extraction operation in the rotary cavitation extractor, the pulp is separated into liquid phase (inulin extract) and solid phase (pectin pulp) , preferably by filtration with a vacuum drum filter with an outer filtering cloth. The filtrate (inulin extract) is collected in an intermediate tank and the solid phase, which typically has 60% - 65% humidity, is fed through a screw transporter to the pectin and fibre production line.

The aqueous inulin extract is purified and concentrated, preferably through ultra-filtration and Diafiltration; preferably by application of the tangential-flow method on ceramic membranes (trademark ISOFLUX), preferably with pore dimensions from 0.14 microns to 0.2 microns. The inulin extract obtained thusly is then fed to a thermal inulin concentration step, preferably with the use of a thin-layer vacuum evaporator, preferably at the a temperature of 60⁰C to 65°C; the inulin is concentrated preferably to a content of 25-28 g/1 and then the inulin concentrate is fed to a spray-drying step with ultrasonic injectors, where the spray-drying with ultrasonic injectors, where inulin drying is preferably performed at the temperature 50⁰C to 65°C.

A white powdered product having 6% - 8% humidity by weight, typically having the following characteristics, is obtained:

- total carbohydrate content: not lower than 90.5% by weight

- inulin: 90%-94% by weight - glucose plus fructose: 4% - 8% by weight

- Ashes: not more than 0.3% by weight

- heavy metals: not more then 0.2% by weight degree of inulin polymerisation: 12 - 16. Inulin yield from Jerusalem artichoke tubers is typically 95% - 98%.

All of the product characteristics provided have been verified through experimental tests performed in the range of process parameters used according to the invention. In table 1 comparative data are reported that illustrate the influence of the process parameters used on the production of inulin.

TABLE 1

For comparison, with the use of a cavitation index equal to 0.15, with times of 15 minutes and inulin drying temperature of 62⁰C, an inulin yield equal to approximately 65% was obtained.

Thus, the method according to the invention provides a substantial increase in the yield of inulin from Jerusalem artichoke tubers, reducing the number of production phases and increasing the effect of purification of inulin, reducing processing losses in the procedure . d) Production of pectins

Following the inulin production phase, the pulp of the Jerusalem artichoke tubers that was separated by filtration and was stored in an intermediate hermetic tank, is fed to a screw press in which a pressing is performed, preferably to a humidity content of 18% - 24% by weight; the pulp provided is then fed through a volumetric doser to the extraction phase in a rotary cavitation extractor; the use of a battery of cavitation extractors arranged in series is preferable. The number of extractors must be sufficient to perform the extraction continuously. In this phase, the water content is regulated to a volume ratio from 1:3 to 1:5 (ratio dehydrated pulp/water) ; the pectin extracting operation is preformed with a cavitation index from 2.1 to 2.3 for a time that is preferably of 45 - 300 seconds .

This operation provides a reduction in time of the quantitative production of the pectinaceous substances from the Jerusalem artichoke pulp, and the production of pectins with high gelation capacity and at the same time the production of high quality, powdered food- grade dietary fibre.

The use of the extraction process with a cavitation index lower than 2.1 results in an increase in the extraction time to more than 300 seconds, which has the consequence of destroying the high molecular weight portion of the substance containing the pectins, lowering their gelation capacity.

The adoption of a cavitation index higher than 2.5 leads to the production of a finely crushed pulp, preventing the complete extraction of the pectinaceous substances from the pulp itself.

The choice of a pulp/water ratio seems to be equally critical when applied to the above-indicated field. Modification of the proportions of pulp/water to values lower than 1:3 or higher than 1:5, when operating with the cavitation indices cited above, leads in all cases, to a decrease in the quantitative yield of the pectinaceous substances and to the reduction of their gelation capacity. The pulp provided following the step of extraction in a rotary cavitation extractor is then separated into liquid phase (aqueous extract containing the pectinaceous substances) and solid phase (finely crushed food-grade dietary fibre) through filtration, preferably in vacuum drum filters and possibly in a filtration centrifuge; the aqueous extract is then subjected to purification, preferably through ultrafiltration and Diafiltration, advantageously with the use of cross-flow on ISOFLUX ceramic membranes, with pore dimensions of approximately 1.4 microns.

Concentration of the aqueous pectinaceous extract is performed in thin-layer vacuum evaporator, preferably at the evaporation temperature of 5O⁰C - 55°C, providing a product having a pectinaceous substance content of 8% - 12%. Final drying of the concentrate is then performed in the spray-drying system at the temperature, preferably, of 50⁰C - 65°C.

The pectin powder provided has the following 5 qualitative and quantitative indices:

- galacturonic acid content: not less than 65% by weight

- volatile substances: not more than 10% by weight

- ash (insoluble in 3 N HCl) : 1% maximum 0 - sulphur dioxide (in dry substance) : 50mg/kg maximum nitrogen content in the pectin (test-tube decalcinated and dried) : 1% maximum

- arsenic: 3 mg/kg maximum 5 - lead: 5 mg/kg maximum

- cadmium: 3 mg/kg maximum

- mercury: 1 mg/kg maximum

- pesticides: absent

- pathogenic micro organisms: absent. 0 All of the above-indicated qualitative and quantitative data were verified through experimental tests performed in the range of the previously described operational parameters.

In table 2 below, comparative data illustrating 5 the influence of cavitation indices on the extraction of pectins from Jerusalem artichoke are reported.

TABLE 2

For comparison, operating with a cavitation index of 1.9 and an extraction time of 30 minutes a pectin yield of 60% with a product having the following characteristics was provided: galacturonic acid content: 52% molecular weight: 64,000

- gelation power: 140° SAG e) Production of fructose-glucose syrup

For the production of the fructose-glucose syrup, part of the inulin aqueous concentrate, coming from the inulin production line, is subjected to hydrolysis with a citric acid solution, preferably at 3% - 5% by weight (pH = 3.5 - 4.2) for 30 - 40 minutes at a temperature from 95⁰C to 120⁰C, preferably 95°C -105⁰C. Performing the hydrolysis under the above-said condition allows maximum hydrolysis to be reached (100%) and darkening of the solution to be avoided, eliminating at the same time the need for a syrup clarification phase on ion- exchange columns .

The hydrosylate provided in this manner, which contains fructose and not less than 50% dry matter, is then subjected to concentration in a vacuum evaporator operating in a cyclic regime and continuously.

After which, the commercial produce is provided, that is, the fructose-glucose syrup of light amber colour, that is sweet to the taste and has a light odour of fruit and caramel.

Performing the concentration in a vacuum evaporator at a temperature of 65⁰C - 7O⁰C, a product that still contains the residual citric acid as a preservative, and therefore does not require the addition of more preservatives, such as sorbic acid, during the preservation phase, is provided.

The use of citric acid at the concentration of 3% - 5% is advantageous, since concentrations lower than 3% lead to an increase in the duration of the hydrolysis (more than 40 minutes) . In addition, in the hydrolysis phase, operating with pressures on the order of 0.41 - 0.45 MPa is advantageous; in fact, reduction of over-pressure to less than 0.41 MPa as well as the use of concentrations of citric acid more than 5% by weight, lead to the formation of an excessive content of citric acid in the final product (syrup).

The temperature interval chosen between 95°C and 120⁰C has been determined through experimental tests performed based, on the kinetic data of the hydrolysis process with citric acid and on the data of the formation of coloured polymeric forms of degradation products of the inulin molecule.

The above-described method for the production of glucose syrup provides a reduction in the number of production phases with respect to the conventional technique, in particular, the syrup neutralisation step with lime milk, adopted in the conventional technique is avoided; in addition, by using citric acid as the hydrolysing agent instead of orthophosphoric acid the step of removing the calcium phosphate deposit, otherwise necessary, is avoided, as is the syrup clarification step by cationic and anionic exchange columns . The fructose-glucose syrup provided is a transparent viscous liquid, with no deposit, cloudiness or extraneous odours .

The syrup provided has the following physicochemical characteristics: - .percentage of dry matter: 60% - 85% by weight - percentage reducing power: 85% - 98% by weight

- percentage of citric acid: 0.01% - 0.03% by weight

- extraneous vegetable substances : absent - extraneous mineral substances: absent

The carbohydrate content in 100 g of 70% fructose- glucose syrup is 64.8 grams; the energetic value is equal to 298 kCal/100 g.

In particular, the technical result provided consists of the reduction of the technological processing of the Jerusalem artichoke tubers, as well as the simplification of the production process and improvement of the organoleptic characteristics of the product provided. f) Production of food-grade dietary vegetable fibre

In a preferred form of embodiment, the method according to the invention provides, in addition, the production of food-grade dietary vegetable fibre; for this purpose the solid portion separated in the pectin production phase, typically having 55% - 65% humidity by weight, is subjected to pressing, preferably with a screw press, and successively dried, preferably in a rotary drum dryer, using hot air, preferably at a temperature of 95°C - 120⁰C, to a humidity of 6% - 8%.

The dry product thus provided, that is, the dietary fibre, does not require further grinding provide a powder, since the solid portion obtained following the extraction of pectins through hydro- acoustic cavitation has a uniformly dispersed composition, in particular, with an average fibre granule dimension of 80 - 120 microns.

The food-grade fibre thus provided can be used both as a food product and as a structural ingredient of low calorie foods. Examination of the physical and chemical characteristics of the food-grade fibre provided shows the following properties:

- absorbing power (water g/1 g fibre) : 23.4 - cholic acid exchange capacity (% of the initial amount) : 34.

These data show that the food-grade dietary fibre provided as the final product of the processing of Jerusalem artichoke tubers according to the method of the invention, is not inferior to the best food-grade fibre provided by cereals (cfr. R. N. Kay, Dietary fiber, J. Lipid Res; 1992, vol. 23, pgs 221-242).

Claims

1. An integrated method for the global recovery and production of carbohydrates, particularly inulin, pectin, fructose-glucose syrup and vegetable fibre from Jerusalem artichoke tubers, in which the crushed tubers are subjected to extraction in water in a cavitation extractor, characterised by the fact that it includes the phases of: a) subjecting the crushed tubers to extraction in water with a volume ratio from 1:3 to 1:8, with a cavitation index from 0.05 to 0.1 for times from 10 to 15 minutes, to provide the extraction in liquid phase of the carbohydrate fraction containing mainly inulin; b) separation of the liquid phase containing inulin from the solid phase through filtration; and c) purification and concentration of the aqueous filtrate containing inulin.

2. A method according to claim 1, characterised by the fact that the phase a) is performed at a temperature from 75°C to 80⁰C.

3. A method according to claim 1, characterised by the fact that the phase c) of purification and concentration is performed through: Ci) purification by filtration and ultrafiltration, on ceramic membranes with pore sizes from 0.14 microns to 0.2 microns; C₂) spray drying at a temperature from 50⁰C to 65⁰C.

4. A method according to any of the claims 1 to 3, characterised by the fact that, for the production of pectins, it includes also the phase of: d) subjecting the pulp of Jerusalem artichoke tubers separated by filtration in phase b) to extraction in water in a rotary cavitation extractor with a mixing ratio of pulp/water of 1:3 to 1:5 and with a cavitation index from 2.1 to 2.5 for a time from 45 to 300 seconds.

5. A method according to claim 4, characterised by the fact that following phase d) of pectins extraction it also includes the phases of: di) separation of the liquid phase by filtration; d₂) purification and concentration of the filtrate; and d₃) drying of the concentrate.

6. A method according to claim 5, characterised by the fact that the phase d₂) is performed through ultrafiltration and Diafiltration, preferably on ceramic membranes.

7. A method according to claims 5 or 6, characterised by the fact that the phase d₂) of concentration of the filtrate is performed in a thin layer evaporator at a temperature of approximately 50⁰C until a product having a content of pectinaceous substances of 8% - 12% by weight is provided.

8. A method according to any of the claims 5 and 7, characterised by the fact that the spray drying phase d₃) is at a temperature from 50⁰C to 60⁰C.

9. A method according to any of the previous claims, characterised by the fact that a portion of the aqueous concentrate containing inulin, produced in phase c) , is subjected to hydrolysis with citric acid to provide a fructose-glucose syrup.

10. A method according to claim 9, characterised by the fact that said hydrolysis is performed with citric acid at a concentration of 3% - 5% by weight.

11. A method according to claims 9 or 10, characterised by the fact that the hydrolysis is performed for a time from 30 to 40 minutes, at a temperature that is between 95°C and 120⁰C.

12. A method according to the claims 10 or 11, characterised by the fact that the fructose-glucose syrup provided in the hydrolysis phase is concentrated in a vacuum evaporator at a temperature from 65°C to 70⁰C.

13. A method according to any of the claims 4 to 12, characterised by the fact that it also includes a step of production of food-grade dietary vegetable fibre, through drying of the solid portion provided from phase d) of the. pectin extraction.

14. A method according to any of the previous claims, characterised by the fact that prior to phase a) , the tubers are washed and crushed and treated with a citric acid solution.