AU7924398A - Acariogenic polysaccharides and method for making same - Google Patents

Description

ACARIOGENIC POLYSACCHARIDES AND A PROCESS FOR THE PREPARATION OF SAID POLYSACCHARIDES The invention provides acariogenic polysaccharides 5 which may be used in particular as a texture agent in products intended to be ingested by man or animals, in particular in food products and in certain pharmaceutical or veterinary products. The invention also relates to a process for the 10 preparation of said polysaccharides and to the application of said polysaccharides to the preparation of acariogenic compositions intended to be ingested by man or animals. The expression "compositions intended to be ingested by man or animals" means compositions or products intended 15 for ingestion and oral administration, such as various foodstuffs such as confectionery, pastry products, dairy ice creams, chewing pastes, chewing gums, prepared animal fodder, and pharmaceutical, veterinary, dietetic or health products such as, for example, elixirs, cough syrups, 20 tablets, pastilles, oral hygiene solutions, tooth pastes and gels. Over the past decade, an increasing amount of interest has focused on the preparation of acariogenic products capable of acting as substitutes for conventional 25 sugars such as sucrose, glucose or fructose in food products and in certain pharmaceutical or veterinary products. The term "acariogenic products" means products exhibiting less acidification by the bacteria of the mouth 30 than the conventional sugars such as sucrose, glucose or fructose. The acariogenic effect is in fact due to the 2 presence in the oral cavity of bacteria which metabolize sugars and lead to the production of acid. The latter dissolves the hydroxyapatite of the dental enamel and creates cavities therein. 5 Acariogenic products of this kind are, for example, hydrogenated monosaccharides, hydrogenated disaccharides, hydrogenated or non-hydrogenated oligosaccharides and hydrogenated polysaccharides. Examples of hydrogenated monosaccharides include 10 sorbitol, xylitol, erythritol, mannitol, arabitol and threitol. Acariogenic disaccharides are represented in particular by maltitol, lactitol, hydrogenated isomaltulose (known by the brand name PALATINIT@ or more is generally by the name ISOMALT) and isomaltitol. Hypocariogenic oligosaccharides are also known already. Examples include maltitol syrups containing about 50-55% of maltitol based on dry matter, for example, LYCASIN@ 80/55 sold by the Applicant. Said hydrogenated 20 oligosaccharides were developed more particularly for an application in boiled sugar sweets. It is evident that much more pronounced hypocariogenic properties are required in an application such as the preparation of boiled sugar sweets which, by their very nature, risk 25 being in contact for a long time with the teeth, than in an application such as the preparation of very dilute liquid products. Other examples of hypocariogenic oligosaccharides also include maltitol syrups containing about 72-78% of 30 maltitol based on dry matter, for example MALTISORB@ 100, 3 MALTIDEX@ 200, MALBIT@ and FINMALT@. However, said syrups cannot be used satisfactorily in certain applications, in particular in boiled sugar sweets, jellies, cough syrups, where another disadvantage is the risk of crystallization 5 during use of said syrups. Polydextroses purified by chromatography (WO-A-92 121 79), hydrogenated polydextroses (WO-A-92 14761) and hydrogenated and chromatographed polydextroses (US-A-5 424 418) are further examples of acariogenic products. 10 Finally, a last category of acariogenic products is composed of hydrogenated polysaccharides obtained by enzymatic hydrolysis of dextrins or polyglucoses (EP-A-561 088, EP-A-561 090, EP-A-561 089, EP-A-368 451 and JP-A 62019501). 15 According to US-A-5 458 892 and US-A-5 236 719, additional treatments of the type including chromatography, treatment with glucose oxidase, gel permeation, ultrafiltration, fermentation by yeasts are, however, necessary for rendering commercial dextrins non 20 cariogenic. It follows from all the above that there is therefore an unsatisfied need for high-viscosity, non-cariogenic polysaccharides obtained according to a simpler process than those already known from the prior art. 25 Contrary to the all expectations, and surprisingly and unexpectedly, the Applicant discovered that it was possible, by extrusion, to obtain polysaccharides which are directly acariogenic, without necessarily hydrogenating them (hydrogenation sometimes 30 creating a regulatory constraint for certain applications) and without necessarily needing to hydrolyze them with enzymes and to 4 separate or hydrogenate the products obtained from hydrolysis in accordance with the processes of the prior art. The invention therefore relates firstly to a process 5 for the preparation of acariogenic polysaccharides comprising the successive steps of: - preparing an acidified starch, dehydrated to a moisture content of less than or equal to 6%, preferably less than or equal to 4%, and more preferably less than or 10 equal to 2%, - extruding the acidified starch thus dehydrated at a temperature in the range 1400C to 230*C, preferably 1500C to 2100C, - collecting the acariogenic polysaccharides thus 15 obtained. One of the objects of the invention is therefore to provide polysaccharides which have the property of being able to be classed as non-cariogenic according to a B test. 20 The invention also provides an acariogenic composition comprising 45 wt.% to 50 wt.% of said polysaccharides and 50 % to 55 % of maltitol. The B test is a test developed by the Applicant in order to monitor the non-cariogenic character of the 25 hydrogenated hydrolysates sold from 1979 onwards under the name LYCASIN@ 80/55. This simple test is based on the in vitro determination of the acidification of a given quantity of hydrogenated starch hydrolysate after seeding the medium with saliva. It is based on an assessment of 30 the pH fall over time of a culture broth containing the 5 product to be tested, therefore after seeding with saliva originating from several donors, in comparison with a reference culture broth not containing any glucid. It should be emphasized that this test is not sufficient to 5 characterize absolutely the non-cariogenicity of a product because its results may vary, for example, depending on the quality of the saliva used, but it nevertheless makes it possible to establish valid comparisons between different products. 10 The detailed operating procedure of this test is as follows. A series of tubes is prepared containing 10 ml of a nutrient culture medium (trypticase medium containing 2% of dry matter) without sugar at pH 7 and said tubes are 15 sterilized by autoclaving at 120 0 C for 20 minutes. 1 ml of sterile water is introduced into a first series of five tubes in order to prepare a reference series. 1 ml of an 18% solution (w/v) of the product to be 20 tested is introduced into a second series of five tubes. The five tubes of each series are then seeded with the same volume of 0.2 ml per tube of a one fifth dilution of human saliva obtained by taking samples from five donors. 25 The formation of acids is then monitored by measuring the pH, a first measurement being carried out before incubation and the other measurements being carried out after incubation at 300C for 3, 6, 13, 18 and 21 hours, respectively.

6 For a product to be regarded as non-cariogenic within the meaning of this B test, the difference in pH observed between the reference after 21 hours and the product to be tested after 21 hours must not be too pronounced and, in 5 practise, at most equal to 1 pH unit. One of the great merits of the invention is that it provides polysaccharides having the property of being non cariogenic within the meaning of this B test while they have not undergone any known treatment to acquire this 10 property. The Applicant has discovered and shown that the acariogenic character of the polysaccharides obtained by extrusion is a direct function of the moisture content of the acidified starch to be extruded. 15 During the preparation of the starch and the conversion thereof by extrusion in the melted phase it is therefore necessary to operate in a slightly hydrated acid medium containing less than or equal to 6% of water, preferably less than 4% of water and more preferably less 20 than or equal to 2% of water, probably so as not to promote hydrolysis reactions and to create branches or crosslinks between the molecules. Processes consisting in extruding a starch have already been proposed in the literature. 25 EP-A-538 146 and EP-A-530 111 describe the preparation of an indigestible dextrin by extrusion of potato and corn starch respectively. Said documents thus relate to obtaining relatively indigestible so-called "low-calorie" products acting in the body as dietary 30 fibers. Their object is thus very far removed from that of the present invention, which is to prepare a 7 hypocariogenic product with technological capabilities that may be used in sweets, chewing gums and tooth pastes and in drinks and pharmaceutical or veterinary elixirs. Moreover, it must be emphasized that the above 5 documents neither disclose nor suggest the importance of the moisture content of the starch to be extruded. With a water content of the acidified starch of less than or equal to 6%, and preferably less than or equal to 4% and more preferably less than or equal to 2%, polysaccharides 10 are obtained which are directly non-cariogenic without it being necessary for them to undergo an additional treatment within the meaning defined above. The first stage of the process according to the invention therefore consists in preparing a dehydrated 15 acidified starch in order to convert it by extrusion. The botanical origin of the starch is unimportant. The starch may therefore originate from wheat, corn or potato. However, it is preferable and advantageous to use wheat starch. 20 The acid used to acidify the starch may be chosen from the group composed of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and citric acid. However, in view of the fact that citric acid is likely to generate undesirable ester bonds, these being responsible 25 for bitterness, and that the handling of sulfuric acid poses obvious safety problems, it is preferable to use hydrochloric acid, phosphoric acid or nitric acid within the context of the invention. The quantity of acid used in the process according to 30 the invention is in the range 5 meq H*/kg to 50 meq H*/kg dry product, and preferably 10 meq Hi/kg to 30 meq H*/kg 8 dry product. It is important that the distribution of the acid in the starch be as homogeneous as possible. Various methods may be used for the acidification of the starch such as batchwise or continuous acidification 5 in the dry or liquid phase. Nevertheless, as the acidified starch is intended to be used in a continuous modification process (extrusion), it is preferable in the context of the present invention to use a continuous means of acidification in order to achieve a process which is as 10 continuous as possible and thus to restrict non-productive operations (loading, unloading, emptying). Once acidification has been carried out, the starch is dehydrated in order to promote re-polymerization reactions during conversion by extrusion. During this 15 drying stage, it is important to ensure that hydrolysis reactions are not promoted because the various parameters favorable to dextrinification (high moisture content, temperature, acidity) are present. These conditions promote undesirable hydrolysis reactions which are 20 characterized by an increase in the levels of reducing sugars. The Applicant was able to show that it was necessary to give preference, during this stage, to continuous drying methods making it possible to achieve the desired 25 moisture content in a residence time of the order of minutes or even seconds and thus to minimize starch hydrolysis reactions. Having thus been dehydrated to a moisture content of less than or equal to 6%, preferably less than or equal to 30 4% and more preferably less than or equal to 2%, the acidified starch may be extruded at a temperature in the 9 range 1400C to 2300C, preferably 1500C to 2100C, to give polysaccharides which are directly acariogenic. The invention therefore relates to acariogenic polysaccharides obtained by extruding a dehydrated 5 acidified starch having a moisture content of less than or equal to 6%, preferably less than or equal to 4% and more preferably less than or equal to 2%. The polysaccharides obtained by extrusion according to the invention are characterized in that they are 10 directly acariogenic without necessarily having to undergo an additional treatment after extrusion to remove the compounds likely to be converted to acids by fermentation, i.e. compounds responsible for dental caries. Within the scope of the present invention, the term 15 "additional treatment intended to remove compounds likely to be converted to acids by fermentation" means, without this list being restrictive on the invention: enzymatic hydrolysis, chromatography, treatment with glucose oxidase, gel permeation, ultrafiltration, fermentation by 20 yeasts, etc. According to another feature of the invention, the polysaccharides obtained by extrusion are directly acariogenic without it being necessary for them to undergo hydrogenation after extrusion. 25 The acariogenic polysaccharides according to the invention have a weight-average molecular weight Mw in the range 2 000 g/mole to 10 000 g/mole and preferably 3 000 g/mole to 7 000 g/mole. They have a number-average molecular weight Mn in the range 900 g/mole to 5 000 30 g/mole, preferably 1 000 g/mole to 2 500 g/mole.

10 The method used for determining the molecular weights is steric exclusion chromatography. It is based on the selective retention of the molecules of solute as a function of their size due to their penetration in the 5 pores of the stationary phase. The polysaccharides in question also have a free reducing sugar content in the range 0 % to 20 % and a free glucose content in the range 0 % to 5%, preferably 0.01 % to 2.5%. 10 The reducing sugar content is expressed as glucose, by weight with respect to the dry weight of product analyzed, and is measured by the BERTRAND method. Due to their physical/chemical and physiological properties, the polysaccharides according to the invention 15 have a certain and immediate advantage, particularly in the preparation of acariogenic compositions intended to be ingested by man or animals. Thus, an acariogenic composition comprising 45 to 50 wt.% of polysaccharides according to the invention and 50 20 to 55 wt.% of maltitol finds an advantageous application in the preparation of boiled sugar sweets. The polysaccharides obtained according to the invention may thus undergo a series of purification stages with a view to decolorizing them. Two methods of 25 decolorization by adsorption may be used, that using activated carbon in powder or granular form and that using adsorbent resins. The ICUMSA (International Commission for Uniform Methods of Sugar Analysis) color defines the color of 30 products synthesized from starch or the hydrogenated equivalents thereof.

11 The principle involves filtering a solution over a membrane to remove the turbidity. The absorbance of the filtered solution is measured at a wavelength of 420 nm and the color of the solution is calculated by the 5 following formula: ICUMSA color = As x 1 000 / 1 x C IU wherein - As is the absorbance of the solution, 10 - 1 000 is a multiplier factor, - 1 is the length of the optical path, - C is the concentration in g/ml of the solution. In the case of a decolorizing stage using activated carbon in powder form, the Applicant has determined that is high decolorization percentages could be obtained using large mesopore pore volumes (radii of the pores in the range 1.5 nm to 25 nm and in particular 4 nm to 20 nm). Successive decolorizing operations may be used to optimize decolorization. However, in order to avoid the 20 loss of activated carbon it is preferable within the context of the invention to use recyclable supports such as columns of granular blacks or specific (adsorbent) resins. Adsorbent resins are very rigid, macro-crosslinked, 25 nonionic or very slightly ionic polymers. They are composed of polystyrene crosslinked with divinylbenzene in the presence of a pore-forming agent. They take the form of. spherical particles with a diameter of 0.5 to 1.5 mm or granules with specific surfaces that may be as much as 30 1 300 m 2 /g, comparable with activated carbons.

12 The use of resins of the MACRONET@ MN 600 type (sold by PUROLITE) is particularly preferred for decolorizing extruded products according to the invention. The extruded, purified product filtered beforehand 5 then demineralized then optionally undergoes molecular sieving then catalytic hydrogenation or catalytic hydrogenation then molecular sieving. This molecular sieving stage may consist in a chromatographic separation stage or a stage of separation over membranes, for 10 example. In the context of the present invention, the molecular sieving stage is intended to remove small molecules from the extruded product. It thus contributes to improving the thermal stability of the product and 15 increasing its viscosity. This molecular sieving stage makes it possible to collect a fraction composed of polysaccharides having molecular weight characteristics determined as a function of the desired viscosity in a given application. Thus, investigations by the Applicant 20 made it possible to show that, for the preparation of boiled sugar sweets, the fraction of polysaccharides having an Mw of about 5 000 g/mole and an Mn of about 2 500 g/mole gave very good results. In the context of the present invention, the 25 hydrogenation stage is intended to improve the thermal stability in the case where, for a given application, the presence of reducing sugars is harmful (which is the case, for example, in the boiled sugar sweet application). Generally speaking, molecular sieving is carried out 30 on a syrup filtered beforehand then demineralized and 13 concentrated to a dry matter content in practise in the range 20% to 60%, preferably 25% to 55%. The chromatographic fractionation stage is carried out in an inherently known manner, batchwise or 5 continuously (simulated mobile bed), over strong cationic resins of the macroporous type, loaded preferably using alkali or alkaline earth ions such as calcium and magnesium but more preferably using sodium or potassium ions. 10 Examples of such processes are described in particular in the following patents: US 3 044 904, 3 416 961, 3 692 582, FR 2 391 754, 2 099 336, US 2 985 589, 4 024 331, 4 226 977, 4 293 346, 4 157 267, 4 182 623, 4 332 623, 4 405 455, 4 412 866, 4 422 881 and WO 92/12179. 15 In a preferred embodiment, chromatographic fractionation is carried out using the process and apparatus described in American patent 4 422 881 of which the Applicant is the owner. Whatever the chromatographic process adopted, the adsorbent preferably used is a strong 20 cationic resin of the macroporous type used in the sodium or potassium form. The resins advantageously have a homogeneous particle size distribution in the range 100 micrometers to 800 micrometers. The choice of parameters of chromatographic 25 fractionation is known to the skilled person. The choice of these parameters is made in such a way that the fraction containing the polysaccharides according to the invention has a weight-average molecular weight in the range 3 000 g/mole to 7 000 g/mole and preferably 4 30 500 g/mole to 5 500 g/mole and a number-average molecular 14 weight in the range 1 000 g/mole to 4 000 g/mole and preferably 2 000 g/mole to 3 000 g/mole. For the hydrogenation stage, it is possible to use both catalysts based on ruthenium and Raney nickel 5 catalysts. However, it is preferable to use Raney nickel catalysts which are less expensive. In practise, 1 to 10 wt.% of catalyst is used with respect to the dry matter of sugar undergoing hydrogenation. Hydrogenation is preferably carried out on 10 syrups of which the dry matter content is in the range 15 % to 50 %, in practise around 30 % to 45%, under a hydrogen pressure in the range 20 bars to 200 bars. It may be carried out continuously or batchwise. In batchwise operation the hydrogen pressure used is 15 generally in the range 30 bars to 60 bars and the temperature at which hydrogenation is carried out is in the range 1000C to 1500C. It is also important to maintain the pH of the hydrogenation medium by adding soda or sodium carbonate, for example, but without exceeding a pH 20 of 9.0. By operating in this manner the appearance of isomerization and cracking products can be avoided. The reaction is stopped when the reducing sugar content of the reaction medium has become less than 1%, preferably even less than 0.5% and more particularly less 25 than 0.1%. After the reaction medium has cooled, the catalyst is removed by filtration and hydrogenated polysaccharides are demineralized over cationic and anionic resins respectively. 30 Other characteristics and advantages of the invention will become clearly apparent on reading the examples below 15 given for guidance but by no means restrictive on the invention. EXAMPLE 1 5 Wheat starch was acidified by hydrochloric acid in a quantity of 21.7 meq H*/kg dry matter, then dried to various residual moisture contents: 6%; 3%; 1.5%. This raw material was then introduced into a CLEXTRAL BC92 extruder having the following technical 10 characteristics: - smooth cylindrical barrel with a fixed length (L 1 000 cm; L/D 10), twin-screws; self-cleaning; multiple-thread; co rotating (diameter of screws: 10 cm), 15 - two barrels heated by induction and cooled by circulation of water, - maximum operating current: 400 A, - maximum rate of rotation: 400 rpm, - maximum operating pressure: 180 bar, 20 and using the following operating conditions: - rate of rotation: 400 rpm, - temperature: 1600C. The product was recovered and characterized in terms of weight-average and number-average molecular weight, and 25 result in the B test (acariogenicity). The results are summarized in Table III below. 30 16 TABLE III Test No. 1 2 3

H

2 0 (%) 6 3 1.5 Mw g/mole 3 420 3 830 4 150 Mn g/mole 1 060 1 130 1 290 B Test Good Good Good B Test Good Good Good (+ 50% maltitol) The extruded product was then purified before undergoing chromatographic separation. The results after 5 chromatography are summarized in Table IV below: 17 TABLE IV TEST No. Mw g/mole Mn g/mole 1 4 560 2 580 2 4 780 2 640 3 5 000 2 500 The product was then concentrated to a dry matter content of about 40% then hydrogenated catalytically to a 5 reducing sugar content of less than 0.5%. EXAMPLE 2 Boiled sweets without sugar were produced from three compositions containing about 50% of maltitol: 10 (A) a maltitol syrup sold by the Applicant under the name LYCASIN@ 80/55; (B) polysaccharides obtained by a conventional process (polysaccharides obtained by submitting a dextrin to an enzyme treatment) to which an equivalent quantity of 15 maltitol had been added; (C) polysaccharides according to the invention to which an equivalent quantity of maltitol had been added. The results are summarized in Table V below. 20 25 18 TABLE V Product A B C Boiling temperature 150 150 150 ("C) Residual water (%) 3.9 2.6 2.3 Glass transition Tg 26.5 49.6 55 (*C) Stability (*) + ++ ++ Quality of completely semi- semi packaging sealed sealed sealed The stability was evaluated after 10 days at 20 0 C and 66% r.h. 5 + sticking ++ slightly deformed and sticky - traces of microcrystals. It was observed that the boiled sweets without sugar prepared from composition (C) according to the invention 10 behaved in a similar manner to conventional prior art sweets. Their behavior differed greatly, on the other hand, from that of boiled sweets prepared from maltitol syrups of the LYCASIN@ 80/55 type which are particularly 15 hygroscopic and tend to run when taking up water. Moreover, Table V shows the other advantages of using composition (C) according to the invention in the preparation of boiled sweets: - surface microcrystallization which leads to a 20 reduction in the cost of packaging; 19 - a reduction in the boiling temperature in order to obtain a boiled mass of less than 97% dry matter (reduction in the cost of energy) whereas, for LYCASIN@ 80/55 (product A) it would be necessary to heat to above 5 150'C in order to bring the residual water content to a value below 3%; - an increase in the glass transition temperature (reduction in the production time).

Claims (10)

1. A process for the preparation of acariogenic polysaccharides comprising steps of: 5 - preparing an acidified starch dehydrated to a moisture content of less than or equal to 6%, preferably less than or equal to 4%, and more preferably less than or equal to 2% ; - extruding the acidified starch thus dehydrated 10 at a temperature in the range 140*C to 2300C, preferably 150 0 C to 2100C, - collecting the acariogenic polysaccharides thus obtained.

2. Acariogenic polysaccharides obtained by 15 extrusion of a dehydrated acidified starch having a moisture content of less than or equal to 6%, preferably less than or equal to 4% and more preferably less than or equal to 2%.

3. Polysaccharides obtained by extrusion which are 20 directly acariogenic without it being necessary for them to undergo additional treatment after extrusion to remove compounds capable of fermenting to acids.

4. Polysaccharides obtained by extrusion which are directly acariogenic without it being necessary for them 25 to undergo hydrogenation after extrusion.

5. Polysaccharides according to any one of claims 2 to 4 which have a weight-average molecular weight in the range 2 000 g/mole and 10 000 g/mole and preferably 3 000 g/mole to 7 000 g/mole. 21

6. Polysaccharides according to any one of claims 2 to 5, which have a number-average molecular weight in the range 900 g/mole to 5 000 g/mole and preferably 1 000 g/mole to 2 500 g/mole. 5

7. Polysaccharides according to any one of claims 2 to 6, which have a reducing sugar content in the range 0 % to 20 %.

8. Polysaccharides according to any one of claims 2 to 7, which have a free glucose content in the range 0 % 10 to 5%, preferably 0.01 % to 2.5%.

9. The use of polysaccharides obtained by extrusion of a dehydrated acidified starch having a moisture content of less than or equal to 6%, preferably less than or equal to 4%, and more preferably less than or equal to 2% as 15 acariogenic compound in the preparation of acariogenic compositions intended to be ingested by man or animals.

10. An acariogenic composition comprising 45 wt.% to 50 wt.% of polysaccharides according to any one of claims 2 to 8 and 50 wt.% to 55 wt.% of maltitol.