MXPA96005214A

MXPA96005214A - Sugar-free coating obtained by hard grageification and its obtenc procedure

Info

Publication number: MXPA96005214A
Application number: MXPA/A/1996/005214A
Authority: MX
Inventors: Serpelloni Michel; Ribadeaudumas Guillaume
Original assignee: Roquette Freres
Priority date: 1995-10-30
Filing date: 1996-10-29
Publication date: 1997-06-01

Abstract

The present invention relates to a new hard crystalline coating based on a particular mixture of polyols. It has in particular the characteristic of having an improved crispiness with respect to the coatings known from the prior art. The subject of the invention is also a process for obtaining this particular coating and an improved process of hard grageification based on xylitol, maltitol or lactitol or its mixtures.

Description

SUGAR FREE COATING OBTAINED BY GRAZING DORA AND Sü PROCESS OF OBTAINING The invention has as its object a new crystalline coating based on a particular mixture of polyols - it also contemplates the process of obtaining this coating by hard grageification. Hard grageification is a unitary operation used in various fields, among which are those of confectionery and pharmaceutical. It can also refer to the industry of additives that are aromatics, sweeteners, vitamins, enzymes, acids and plant-based products. This operation consists of using a crystalline hard coating on the surface of the solid or powdery products in order to protect them for various reasons or to make them attractive visually or gustatively. In very general terms this unitary operation is carried out by placing these products as cores in subject to coating, in a grageification turbine. The purpose of hard grageification is to obtain a crunchy and sugary layer, which is always highly valued in the case of confectionery or chewing gums. It always requires the use of a syrup and / or a suspension containing crystallizable materials. The hard and crystalline coating is obtained later by application of this syrup or of this suspension in the cores and the evaporation of the water contributed by these, thanks to a drying with hot and dry air, which causes the crystallization. This cycle must be repeated for a large number of times, that is, on the order of ten to eighty times in order to obtain the desired rate of increase. It is generally called the rate of increase, the growth in weight of the products, considered at the end of the operation in relation to the beginning, and referring to the final weight of the products. Hard grageification can be preceded or followed by other wrapping techniques. In particular, the following techniques can be pointed out, which are also frequently carried out using a grageification turbine: - gumming, which is a technique in which syrups of non-crystallisable materials and in general non-hygroscopic materials such as gum arabic, starches are used and the modified celluloses, the maltodextrins. This technique allows, after one or two applications of the gumming syrup in the product subject to coating, to create a glassy film that constitutes a flag for the migration of oxygen, water or fats. In this process, together with these non-crystallizable syrups, powders of different characters can also be used to fix the water provided by the syrups. In still other cases, sugars or polyols melted or liquefied by solvents are used. The glassy, hard and cracking coating is then obtained by cooling or by evaporation of the solvents. - tender or soft grageification consisting of creating a very flexible and soft coating on the surface of the products. This coating is obtained by repetitive applications, on the one hand of a non-crystallizable syrup, in general the hydrolysates of starches and on the other hand of a powder, generally crystallized sucrose. The coating is usually thick. The rate of increase for this technique is of the order of 10 to 80% and even more. It should be noted that the matter constituting the syrup is usually different from that of the powder. - polishing consisting of the use of fatty substances or waxes that are generally supplied in crystallized form, such as pips, or in the form of alcoholic solutions, in order to coat the products with a very thin film, grease, in order to reduce the Transparencies of water from or to the wrapped products but also to beautify its surface. The hard grageification term used in the present invention also comprises the very similar techniques that are smoothing and frosting. The smoothing consists of one or two applications or loads of a crystallizable syrup diluted with respect to that used in hard grageification. The object is often to achieve the appearance of a surface of grageificados products. The frosting in turn also aims to improve the appearance of the products but also to isolate the latter from the humidity of the atmosphere. This technique resembles a hard grageification in the sense that vin crystallizable syrup is used. However, the essential difference lies in the fact that the number of cycles performed is only one, two or three and nothing more. Therefore, there is interest within the framework of the present invention for the hard grageification itself, in the smoothing, frosting as well as in these combined techniques. A hard grageification is often followed by a smoothing. Several of these wrapping procedures have been applied using polyols. Polyols are usually understood, as in the present invention, sugar alcohols which are obtained by reduction of sugars. More precisely, in the context of the invention, the interest is concentrated in mannitol. There is also interest in particular polyols such as the following: xylitol, maltitol and lactitol. Finally, there is interest in the mannitol of glucose 1-6 (or alpha-D-glucopyranosyl-l-6-mannitol) and in the mixtures of polyols containing this molecule such as isomalt. With a sugary taste generally inferior to that attributed to sucrose, which tend to replace in human food but also in pharmaceutical and dietetic formulations, polyols have the advantage of not being cariogenic and have a fixed caloric value in Europe equivalent to two thirds of that of sugar. Among the polyols, only considering the current situation, sorbitol is marketed in the form of syrups of high hardness, directly usable in hard grageification, especially according to the procedure that is the object of patent EP 037,407. As regards xylitol, maltitol or lactitol, in which there is a special interest within the framework of the present invention, it is usual, in order to proceed with a hard grageification, to dissolve one of these polyols in water in advance in water in order to prepare crystallizable solutions in this way. It has always been considered indispensable to use, by analogy with what is done for sucrose, powders of a very high level of purity to allow rapid and facilitated crystallization of the preserved polyol from the solution or suspension used in hard grageification. This obligation is cited for example in the article by F. BOU IN "Sugarless panning procedures and techniques" The Manufacturing Confectioner, 1992, 77-82. It is said that the rate of crystallization depends directly on the purity of the syrup of the polyol used. The author refers to sucrose for which he points out that he has discovered that this speed is reduced by half when its purity is only 95%, that is, in relation to pure solutions. As regards the hard grageification with xylitol, outside of the demarcations of this article, the need to preserve or use high purity xylitol in the following documents is directly or indirectly mentioned: - the French patent FR 2.342.668 of the FERRERO company, which also states that it is imperative to use xylitol containing at most 5% other polyols such as sorbitol and / or mannitol; - US Pat. No. 4,127,677 in the name of the company LIFE SAVERS, in which the use of a solution containing dry from 95% to 99.5% of xylitol, obtained by cold dissolving crystalline xylitol and then heating the mixture; - the document "FOOD TECHNOLOGICAL EVALUATION OF XYLITOL "by F. VOIROL, ADVANCES in FOOD RESEARCH, 1982, vol.28, 373-403, where it is simply pointed out that it is advantageous to prepare a solution on saturated at 85% dry matter in xylitol: - European patent EP 273,000 the society WARNER-LAMBERT Company in which an edible product coated with an envelope consisting of 40 to 70% xylitol is described, the complement being formed to form 100% of at least one smoke agent, at least one binder and at least one mineral filler and optionally at least one plasticizer. This patent also claims a grageification process consisting of the successive use of three grageification syrups that at all times contain in relation to their dry matters, less than 35% of a sugar or a polyol, in particular xylitol; - and the US patents US 4,681,766 and US 4,786,511, of which the company also owns: WARNER-LAMBERT Company, and which describes a hard grageification solution and a grageification coating containing both from 30% to 80% of a sweetener, preferably xylitol, from 1% to 15% gum arabic and from 0.05% to 10% of a calcium salt. In several documents it also points out the possibility of carrying out a hard grageification with the use of maltitol, to the extent that the purity of this polyol is very high. This is the case in particular in the following documents: European patent EP 201,412, whose applicant is the owner, where a process for grageification using a maltitol syrup with a purity higher than 92% is disclosed at the same time and a product having a crystalline hard coating containing at least 90% maltitol; - and Japanese patent application JP 61.263915 in the name of the company HAYASHIBARA, which refers to the use in the hard grageification of a syrup containing maltitol with a purity greater than 90% and a cohesion agent. As regards isomalt grageification, it is also known from US patents 4,792,453 and 5,248,508 from WRIGLEY, where only as a polyol isomalt is dissolved in water to prepare the grageification solutions. Hard grageification with lactitol is also known. In this case, it also seems that nowadays it has never been contemplated to use it in any other way than as a hard polyol. In the case of mannitol, although it has been pointed out in the European application EP 308,317 deposited by the company SANOFI, the possibility of carrying out a hard grageification with mannitol, without concretely giving, on the other hand, the conditions of such operation, turns out to be very difficult to achieve such a purpose. This has been confirmed in the document of F. DEVOS "Coating with sorbitol, a comparison of properties of sorbitol-mannitol, other polyols and sucrose" in The Manufacturing Confectioner, 1980, vol. 60 p. 26, where the author explains that the solubility of mannitol is very weak to allow good conditions of hard grageification and that an excessive amount of water would have to evaporate in such case. This explains that there has never been a grated product with mannitol in the market before. In conclusion, there is a widely popularized postulate today, according to which it is convenient to use a single pure polyol in a fast and satisfactory way with a hard grage with polyols. This is not in contradiction, quite the contrary, with the basic principles of two of the most recent techniques known for hard grageification, as described below. The first of these two techniques, which is described in particular in US patents and patent applications US 5,270,061; the international WO 93/18663, the international WO 95/07621 and the international WO 95/07622 of the WRIGLEY company consists of a "dual" or "double" grageification. It's about starting the grageification with a syrup that contains a pure polyol like xylitol, maltitol or lactitol to then continue and finish it by using another polyol syrup equally pure but different in nature from the first polyol, such as isomalt. This double grageification technique contemplates essentially reducing the cost of grageification by partially replacing one polyol with another and reducing the hygroscopicity of the grageified layer. On the other hand, time seems to be quite expensive and difficult to take to an industrial practice. The second recent technique is disclosed in the European patent application EP 625,311 whose successor in title is the owner. Thus, the system is claimed to successively apply a high purity polyol syrup and a powder containing the same polyol in the pure state and, as usual, do not proceed with a forced drying by hot dry air in the gravity turbine. This procedure makes it possible to reduce the grageification times to a high degree and obtain relatively crispy coatings after being stored for several hours. Apart from the search for resources that include reducing the costs of hard grageification with polyols and especially reducing grageification times, it has often been tried to find solutions tending to increase the formation of crust and the crisp appearance of the grageified coatings. with polyols. These factors, like the taste, act directly on the level of acceptance of the products and on the renewal of purchasing operations by consumers. According to G. RIBADEAU DUMAS in his lecture entitled "Actual manufacturing possibilities for sugarless hard and soft coating techniques - problems - solutions" in SüBwaren - Dragee - Tagung, Mai 1994, Solingen, Zentralfachschule der Deutschen SüBwarenwirtschaft eV, crust formation is a subjective and complex organoleptic magnitude which, on the other hand, can be controlled by mechanical measures of hardness and friability with the help of an INSTRON type device. Thus, it has been possible to objectively demonstrate that scab formation varies with the characteristics of the nucleus subject to grageification, as in the case of those of the grage layer. The nature of the preserved polyol to prepare the grageified layers, the water content of the grageified layers at the end of the grageification as well as the water activity, are described as factors that act directly on the crust or crunching character. However, unfortunately the replacement of one polyol by another to obtain a crunchy character or improved crust state is not without consequences with respect to the other essential organoleptic characteristics of the grageified layer which are the sugary taste, whiteness or freshness in the mouth so that in general terms it is incompatible with the wishes of consumers. Thus, the author of the cited conference has pointed out that when the crust formation is the crunchy character it is insufficient that a purer polyol must be preserved or applied before replacing one polyol with another. As regards the adjustment of the characteristics of the nucleus subject to grageification, there are possibilities of improvement, however, such possibilities in general terms are quite limited. Finally, lowering the residual water content of the grageified layers to increase the crispiness in general is possible at all times but this is inevitably accompanied by an increase in manufacturing times and energy costs, which is a particularly important factor. annoying. Other solutions also seem to have been proposed to improve in particular the crunchiness of the sugar-free hard grageified layers based on polyols. It has been very frequently recommended that substances other than polyols be incorporated into grageification syrups. This is the case, for example, in the European patent EP 229,594 of the company WARNER-LAMBERT which recommends associating with the polyol used, polyvinyl pyrrolidone. Other authors have proposed to use, in addition to gelatin and gum arabic, whose use is very old grageification, binders such as modified celluloses, glucose syrups, pullulan or various gums, with relatively low percentages, generally less than 5% dry . It has been found that these substances improve the adhesion of the grageified layer to the core as well as the cohesion of the grageified layer. They also act to some extent on the crunchy character, that is, crusting. However, it seems that the addition of such viscous substances significantly disturbs the crystallization of the polyol used so that the grageified layer has a lower crystallinity. This would explain that in such a case it would have a tendency for the crystallinity to become sticky. Nor do these substances allow to reduce the grageification times, on the contrary, they increase them. The applicant has surprisingly and unexpectedly noticed that the addition of mannitol in the syrups or grageification suspensions based on xylitol, maltitol or lactitol, in a proportion of 20% to 50% dry with respect to the dry polyols present , allows both to reduce the grageification times and increase the crispness of the coatings thus obtained. Contrary to anything expected, the applicant realized that mannitol, as a voluntarily introduced impurity, far from retarding the crystallization of xylitol, maltitol or lactitol, had an effect in favor of crystallization, at certain very precise concentrations, ie which accelerates the crystallization of these polyols from aqueous saturated or supersaturated media as in the case of hard grageification syrups. In addition, when this material is incorporated in a sufficient portion, that is to say in more than 20%, an effect that draws attention is noted, at the level of the crust formation and the crunchiness of the grage layer. On the other hand, beyond 50%, the successor noticed that mannitol loses its beneficial role on the crust-forming character and that the times required for grageification tend to increase again.

Continuing with their investigations, I can establish the successor that the roles in favor of crystallization and of agent that improves scab formation, discovered by mannitol, could also be performed by glucose -1,6-mannitol. In this case, it is necessary to apply an addition rate, in dry, with respect to the dry matter constituted by polyols present in the grageification syrup, from 5% to 50%. The successor could also establish that it is possible to use a mixture of polyols containing mannitol and / or 1,6-mannitol glucose, subject to sting the employment rates, which poses no particular problem. Thus, in short, the currently popularized postulate according to which the grageified layers can not be obtained quickly with excellent crispiness more than with the use of a polyol of a very high purity, although in general terms it is still valid, it has not been proven when mannitol or glucose-1,6-mannitol is added as an impurity, and this in a very specific amount. The invention therefore contemplates, in the first instance, a new hard crystalline coating containing at least 90% of a mixture of polyols, constituted, in dry form, by about 20 to 50% mannitol or about 5 to 50% of glucose - 1,6-mannitol. The complement up to 100% of the dry matter of the mixture is constituted basically by a polyol selected from xylitol, mannitol or lactitol.

The crystalline coating according to the invention may contain pure mannitol or glucose-1,6-mannitol crystals intimately mixed with pure crystals of xylitol, mannitol or lactitol. Such a coating can be obtained for example by crystallizing the surface of a core, a syrup containing dissolved state of xylitol, mannitol or lactitol and in the crystallized state of mannitol, glucose-1,6-mannitol or any substance containing one or the other of these two polyols. The crystalline coating according to the invention can also be constituted by the so-called "co-crystals" which are composed on the one hand of mannitol or of glucose -1,6-mannitol and on the other hand of xylitol, mannitol or lactitol. By "co-crystals" is meant the crystals obtained by crystallizing together, from a supersaturated solution, on the one hand mannitol, xylitol or lactitol and on the other hand mannitol or glucose-1,6-mannitol. Advantageously, the polyol mixture constitutes more than 95% of the coating according to the invention and even better, more than 95% thereof. The latter can therefore also comprise other substances. Mention may be made, without the list being exhaustive, of substances such as flavors, intense sweeteners, dyes, bleaching agents such as talc or titanium dioxide, mineral fillers, binders, such as, for example, gelatin and gum arabic, fats, waxes or lacquers and also water. Generally, the water content is lower than 1.5%, preferably lower than 1.0% and even better lower than 0.5%. This coating can be made using very diverse products as the core subject to grageification. They can be food products such as confectionery, such as chewing gums, tablets, pills, jellies, eggnog, chewing pastes, hard candies, chocolate-based products but also pharmaceutical or veterinary products such as pills, tablets, products for animals, dietetic products, granulates of plants and other products such as seeds, dried fruits, grains, powders of agglomerated fertilizers or also additives based on enzymes or microorganisms intended in particular for the manufacture of foodstuffs such as bread or industrial products such as bleaches or other detergent powders or cleaners, powdery additives composed of vitamins, aroma, perfumes, acids, sweeteners or various active ingredients. According to a first embodiment, the crystalline coating according to the invention comprises mannitol and another polyol selected from xylitol, mannitol or lactitol. Preferably, according to this embodiment, only one of these three polyols is associated with mannitol. Advantageously, the latter represents dry from 20 to 40% of the dry matter of the constituent mixture of the coating, and even better from 22 to 35% thereof. Indeed, it has been noted that the results in terms of crisp quality and speed of grageification are the best for these values. It is also preferred to use mannitol with a purity greater than 95% and even better, higher than 98%. According to a second embodiment, the crystalline coating according to the invention comprises glucose -1,6-mannitol and another polyol selected from xylitol, mannitol and lactitol. Preferably, glucose-1,6-mannitol is associated only with one of these three polyols. Advantageously, according to this particular mode, glucose-1,6-mannitol represents in dry form 10% to 40% and better 15% to 35% of the dry matter of the mixture of the polyols constituting the coating. These values are particularly good when the glucose-1,6-mannitol has a high degree of purity, ie greater than 75% and preferably greater than 90%. When this purity decreases and no longer reaches approximately 50%, as in the case of the use of the product called isomalt, the preferred contents are lower and are between 5% and 20% and even better between 5% and 15%. Based on these considerations, a few simple routine tests are sufficient to determine the content of glucose-1,6-mannitol that should be used according to its degree of purity, in order to obtain the best results in terms of crispiness and grageification speed. . The crystalline coating according to the invention, due to its high crunchy character, can constitute an interior, intermediate or outer coating of complex coatings such as those prepared by double grageification or those composed of several grageified layers of different character or texture. The invention relates in the second place to a process for obtaining by hard grageification, a hard crystalline coating having the characteristics defined above. The hard grage process according to the invention comprises, in its general mode, the following steps: the placement in rotation movement of the cores that must be grageified in a grageification turbine; - the creation on the surface of the cores of a semicrystalline coating containing at least 90% of a polyol mixture, provided by repeated applications of at least one crystallizable liquid composition or at least one crystallizable liquid composition and at least one crystallized composition. The polyol mixture is constituted on dry by approximately 20% to 50% mannitol or about 5 to 50% glucose-1,6-mannitol, the complement being constituted up to 100% of the dry matter essentially by a polyol selected from xylitol, mannitol or lactitol; - preferably a drying of the coating, inside or outside the gravity turbine, to allow more complete crystallization of mannitol or glucose-1,6-mannitol and at least one of the complementary polyols. As far as the first stage of the process is concerned, the cores to be coated are subjected to turbine treatment, that is to say a rotary movement in a grageification turbine. This turbine can have a common shape, ie a tulip shape with an inclined revolution axis or a cylindrical shape with a horizontal axis. The cores, preferably devoid of powder before or after their introduction into the turbine, preferably have a spherical, cylindrical or oval shape in order to facilitate the operation of the envelope but may also have a bearing shape. The second stage consists of creating a semicrystalline coating composed of a mixture of particular polyols to the surface of the cores. According to a first embodiment, only crystallizable liquid compositions are applied to the surface of the cores. It can be in particular of the following compositions: a solution containing in the dissolved state both mannitol or glucose 1,6-mannitol and at least one other polyol selected from xylitol, mannitol and lactitol. Preferably, these solutions have a saturation level in xylitol, mannitol or lactitol comprised between 0.8 and 1.2, or - a suspension containing, in the dissolved state and in the crystallized state, both mannitol and glucose-1,6-mannitol and minus another polyol selected from xylitol, mannitol and lactitol. These compositions are necessarily crystallizable, that is to say able to generate by water evaporation the crystallization of mannitol from glucose-1,6-mannitol and at least one of the complementary polyol. According to this embodiment, an appropriate amount of liquid crystallizable composition is sprayed onto the surface of the cores, this amount is allowed to be distributed to obtain a thin film of a crystallizable liquid composition and preferably a thin film of the surface of the cores. Dry by blown in the turbine with dry and hot air to allow crystallization. This cycle, as in the case of a classical grageification, can be repeated many times to obtain the desired rate of increase. According to a second embodiment, at least one of the liquid crystallizable compositions defined above but also at least one crystallized composition is applied to the surface of the cores. By "crystallized composition" is meant any powdery composition containing in the crystallized state at least one of the polyols selected from mannitol, glucose-1,6-mannitol, xylitol, mannitol and lactitol. According to this second embodiment, a crystallized liquid composition is applied to the surface of the cores that must be coated on the one hand and, on the other hand, after the latter has been distributed, a crystallized composition. The polyols which constitute these two types of compositions are selected in such a way that the coating contains at least 90% of a polyol mixture constituted in dry form by approximately 20 to 50% mannitol or approximately 5 to 50% glucose-1., 6-mannitol, the complement or moiety being constituted to form 100% of this dry matter by a polyol selected from xylitol, mannitol and lactitol. The last, optional but convenient step of the process according to the present invention consists in drying. It can be carried out inside the grageification turbine by blowing dry or hot air or outside it, for example by placing the cores coated with the semicrystalline mixture in a baking chamber. This step contemplates allowing the more complete crystallization of a part of mannitol or of glucose-1,6-mannitol and on the other hand of the complementary polyol selected from xylitol, mannitol and lactitol. Instead of proceeding with this step, it is also possible to allow the semicrystalline coating to evolve naturally to a crystalline state. The successor has noticed that the crust formation and crunchy condition obtained depend both on the level of crystallinity of the coating and on its water content. Through organoleptic tests and also by measurements of hardness and friability with an INSTRON brand model 4502 device, he noticed that the crust formation of the coating containing mannitol crystals or glucose-1,6-mannitol and crystals of at least A complementary polyol chosen from xylitol, mannitol and lactitol is clearly larger than the scale formation of control or control-type coatings according to the prior art, which consist only of the same complementary polyol. By comparative thermodynamic measurements between coating according to the invention and coatings corresponding to the prior art, it is thus found that, contrary to what might be thought by the results obtained from organoleptic and rheological studies, the melting enthalpies of the coatings according to the invention are smaller than those of the prior art coatings. In effect, these values are usually below 5 to 25%. By way of example, all other factors remaining the same, the enthalpy of fusion of a coating according to the invention consisting of xylitol and mannitol in respective dry proportions of 78% and 22% with respect to the group of the polyols present are only 170 J / g while the enthalpy of a coating of the prior art consisting only of xylitol is about 215 J / g. The melting point of the coating is generally lower. In the above example, the melting point of the prior art coating is close to 93 ° C while it is not more than a level of about 87 ° C for the coating according to the invention. As regards the water content, it is preferred that, thanks to the final drying, it should be lowered to a value lower than 1.5%, preferably lower than 1.0% and more preferably lower than 0.5%. The applicant company has found that the method according to the invention allows the desired rate of increase to be obtained more quickly, compared to or compared to prior art processes of the same type in which it is used only as polyol, xylitol, mannitol or lactitol. Less dust formation has also been noted in the grageification turbine and in the grage shop when only liquid crystallizable compositions are used, which is particularly advantageous in comparison with the prior art. Thirdly, the invention relates to a process that improves the speed of grageification and the crust formation of the coatings obtained by hard grageification with the help of a polyol chosen from xylitol, mannitol, lactitol and their mixtures, which consists of replacing: mannitol at 20 to 50%, preferably 20 to 40% and more preferably 22 to 35% of the polyol chosen, or - glucose - 1,6-mannitol in 5 to 50%, preferably 10 to 40% and more preferably 15 to 35% of the chosen polyol. The invention also contemplates the use of mannitol or glucose-1,6-mannitol for this purpose and in the amounts specified above. The gains obtained in terms of speed of grageification and crusting in relation to the prior art are usually at least 10%. The means for the practical realization of this method as well as the advantageous characteristics of the new coating according to the invention will be better understood in the light of the following examples, which are not limiting. EXAMPLE I: Preliminary Tests These tests are reported in order to highlight the specific roles of mannitol and glucose-1,6-mannitol on the crystallization of xylitol, mannitol and lactitol in comparison with other polyols. For this purpose, solutions with 75% dry matter are prepared, containing: - xylitol only, - mixtures of xylitol / other polyol in respective proportions (dry envelope) of 95% / 5% of 90% / 10% and 78% / 22% As the other polyol, the products of a very high purity are applied, as follows: sorbitol, arabitol, mannitol, maltitol, glucose, 1,6-mannitol, obtained by fractional crystallization of isomalt. The solutions are prepared according to the following standardized mode of operation: - solubilization at 60 ° C, - adjustment of the dry matter, - maintenance in a closed vessel in a water bath at 100 ° C for 1 hour. Then the set of solutions (total 16) is placed at 20 ° C for 13 days. It is noted that during this period, only four preparations have evolved towards a crystallization of xylitol. These are the solutions that contain on dry: - 90% xylitol and 10% mannitol, - 90% xylitol and 10% glucose - 1,6-mannitol, - 78% xylitol and 22% mannitol, - 78% xylitol and 22% glucose - 1,6-mannitol. Solutions containing 22% glucose-1,6-mannitol or 22% mannitol crystallized only after 2 days while the other two solutions evolved in the same way but after 5 days for mannitol and after 7 days for the material with glucose - 1,6-mannitol. The whole of the preparations not changed after 13 days at 20 ° C (in total 12) are subjected to several thermal cycles comprising a phase of 12 hours at 4 ° C and a phase of 12 hours at 20 ° C. It is noted that the pure xylitol solution crystallizes after one cycle, only. Considering the solubility in water of xylitol that is 62.7% at 20 ° C, it can be noted that the initial solution has remained unchanged in an oversaturated state for 13 days that a single temperature drop at 4 ° C has been sufficient to cause the crystallization of xylitol. After 4 cycles of 12 hours at 4 ° C and 12 hours at 20 ° C, the appearance of xylitol crystals in the dry compound solution was observed by 95% xylitol and 5% glucose-1,6-mannitol. The set of other solutions (in total 10) has remained unchanged with respect to the initial state, even after 7 thermal cycles. It is concluded from these tests that surprisingly mannitol and glucose-1,6-mannitol accelerate the crystallization of xylitol from a supersaturated solution but under the condition of being used in a sufficient concentration (greater than 10%). In effect, these same two polyols have a reverse effect at low concentration. The effect in favor of the crystallization of mannitol and glucose-1,6-mannitol at certain concentrations can be exploited to accelerate the hard grageification rate in the case of xylitol. It is noted that the other polyols used (sorbitol, mannitol and arabitol) only retard the crystallization of xylitol and due to this fact are authentic anti-crystallization of xylitol. The pro-crystallizing effect of mannitol and glucose - 1,6-mannitol at certain concentrations, it also exists in mannitol and in lactitol as proven by the successor in agreement with other tests of the same type. By way of example, the Applicant has observed the pro-crystallizing effect of mannitol on maltitol at the level of a preparation at 70% dry matter containing respectively 70% maltitol and 30% mannitol. EXAMPLE II Preparation of coating according to the invention and according to the prior art. 2.1) Preparation: The cores are gragged for chewing gum in the form of a bearing using polyol compositions which all have a dry matter of 75% and which all contain on dry 98.7% polyols and 1.3% gum arabic. For this purpose, four different compositions are used: the syrup A: this does not contain more than xylitol as a polyol; - it is a syrup according to the prior art; - the syrup B containing 90% xylitol and 10% mannitol as a polyol, - the syrup I2 containing 79% xylitol and 21% mannitol as a polyol, - and the I2 syrup containing 75% polyol of xylitol and 25% mannitol. To avoid eventual crystallization, the four syrups are maintained at a temperature of 70 ° C. Four hard grageification tests are carried out using each of the four syrups throughout the time of the grageification. For this purpose, 1 kg of cores are placed in a grageification turbine, in the shape of a tulip. Each of the compositions is sprayed in a ratio of 10 ml onto the rotating cores. After distributing this amount, the cores are dried by ventilation with dry and hot air. At the end of this cycle, the system is repeated in an identical way, progressively increasing the amounts applied, and this until obtaining an increase level of 20%. Half of the grageified products are then extracted from the turbine. It is continued for the other half with the grageification until obtaining an increase rate of 30%. It is noted that to reach the same rate of increase, the time of grageification is less with the syrups containing mannitol and this is all the more so as the amount of mannitol is considerable. A lower dust formation is also noted with the syrups I, and I2 as in the case of syrups A and B. 2.2 Organoleptic quality of the obtained coatings The four types of coatings obtained are submitted to a panel of experts to qualify the formation of crust or crunchy character (0: very weak and 5: a very good crust formation). The highest marks with the same rate of increase are obtained by the crystalline hard coatings, prepared by using syrups I, and I2. 2.3) Comparative measurements of hardness and friability of coatings according to the invention according to the prior art. It is studied with the help of an INSTRON Model 4502 material, the hardness as well as the friability of a coating according to the invention (syrup I,) and a coating according to the prior art (syrup A) as obtained above with a of 20% and 30% increase. These coatings contain 0.7% water. The hardness thus measured corresponds to the force necessary to obtain the first breakage of the coating, related to the penetration distance of the punch used. The friability, in turn, corresponds to the number obtained of the coating breaks for a penetration imposed by the punch used. These two values allow calculating a value of crust formation (INSTROND) directly correlated with the results of crust formation that is obtained thanks to a jury of experts.

Rate of increase 20% 30% Syrup I Syrup A Syrup I Syrup A It is noted that the coatings according to the invention, although they are clearly less hard, are obviously more friable and more crisp. 2.4) Thermodynamic study The coatings according to the invention obtained by using the syrups I1 and I2 have melting points between 82 and 89 ° C while the melting point of the coating according to the prior art is of the order of 93 ° C. It should be noted that only a single melting point is disclosed for the coatings according to the invention as obtained above although they contain both xylitol and mannitol. The enthalpy measured for the coatings according to the invention is between 160 and 180 J / g while it is about 215 J / g for the coating according to the prior art. 2.5 Observation under the electron microscope It is noted that at least certain areas of the coatings according to the invention contain two populations of crystals. Some of them, few in number, with an elongated and parallelepiped shape, resemble ordinary mannitol crystals; the other crystals of a more compact and less elongated form resemble common xylitol crystals. EXAMPLE III Preparation of coatings according to the invention and according to the prior art. 3.1) Preparation: The chewing gum nuclei are grageified in the form of a bearing using polyol compositions having all a dry matter of 75% and containing all on dry 98.7% polyols and 1.3% gum arabic. For this, two different compositions are used: the syrup A: this does not contain as a polyol more than xylitol; - it is a syrup according to the prior art; - the syrup I3 containing as polyols 75% xylitol and 25% mannitol. To avoid its eventual crystallization, the two syrups are maintained at a temperature of 70 ° C. We proceed with two tests of hard grageification using each of the two syrups throughout the time of the grageification. For this purpose, 3 kg of cores are placed in a tulip-shaped turbine. Each of the compositions is sprayed in a proportion of 30 ml onto the rotating cores. After distributing this amount, the cores are dried by ventilation with dry and hot air. Once this cycle is completed, the cycle is repeated in an identical manner but progressively increasing the quantities applied until obtaining levels of 20% increase. 3.2) Quality of the chewing gums obtained and advantages of the process: The time necessary to grage the nuclei of the chewing gums is shorter when the syrup I3 according to the invention is used, in comparison with the syrup A according to the technique previous. The chewing gums obtained according to the invention obtained an excellent note of crust formation during the tasting by the jury of experts. In addition, the thermodynamic analysis of this crystalline coating according to the invention showed that it had a melting point of 84.5 ° C and a melting enthalpy of 146 J / g. EXAMPLE IV Preparation of coating according to the invention and according to the prior art. 4.1) Preparation: The chewing gum nuclei are grageified in the form of bearing by use of polyol compositions that all have a dry matter of 75% and all contain on dry 98.7% polyols and 1.3% gum arabic. For this, two different compositions are used: the syrup A: this only contains as a polyol, the xylitol; it is a syrup according to the prior art; - the syrup I4 containing 78% xylitol and 22% glucose-1,6-mannitol as polyols. To avoid its eventual crystallization, the syrup according to the prior art is maintained at a temperature of 70 ° C while the syrup I4 according to the invention is only maintained at a temperature of 50 ° C. We proceed with two tests of hard grageification using each of the syrups throughout the duration of the grageification. For this purpose, 3 kg of cores are placed in a tulip-shaped turbine. Each of the compositions is sprayed in a proportion of 30 ml onto the rotating cores. After distributing this amount, the cores are dried by ventilation with dry and hot air. Once this cycle is over, the amounts applied are repeated in an identical manner but progressively increased until 20% increase rates are obtained. 4.2) Quality of the chewing gums obtained? Advantages of the process: The time necessary to grage the nuclei of the chewing gums is shorter when the syrup I4 according to the invention is used, compared to syrup A according to the prior art. Furthermore, the maintenance of the syrup I4 according to the invention at a temperature of 50 ° C was sufficient to prevent its crystallization. This constitutes a non-negligible economic advantage that will be appreciated by the person skilled in the art. The chewing gums obtained according to the invention obtained an excellent note of crust formation during the tasting by the jury of experts. In addition, the thermodynamic analysis of this crystalline coating according to the invention showed that it had a melting enthalpy of 170 J / g. EXAMPLE V Preparation of coating according to the invention and according to the prior art. 5.1) Preparation: The chewing gum nuclei are grageified in the form of bearing by use of polyol compositions having all a dry matter of 75% and all of them contain on dry 48.7% polyols and 1.3% gum arabic. For this purpose two different compositions are used: - Syrup A: this only contains as a polyol, mannitol; it is a syrup according to the prior art; - the syrup I5 containing 50% mannitol and 50% glucose-1,6-mannitol as polyols.

To avoid its eventual crystallization, the syrup according to the prior art is maintained at a temperature of 70 ° C, while the syrup I5 according to the invention is only maintained at a temperature of 50 ° C. We proceed with two tests of hard grageification using each of the two syrups for the entire duration of the grageification. For this purpose, 3 kg of cores are placed in a tulip-shaped turbine. Each of the compositions is sprayed in a proportion of 30 ml onto the rotating cores. After distributing this amount, the cores are dried by ventilation with dry and hot air. Once this cycle is completed, repeat it in an identical manner but progressively increase the amounts applied until obtaining 20% increase rates. 5.2) Quality of the chewing gums obtained? Advantages of the process: The time necessary to grage the nuclei of the chewing gums is shorter when the syrup I5 according to the invention is used, compared to the syrup A according to the prior art. Furthermore, the maintenance of the syrup I5 according to the invention at a temperature of 50 ° C was sufficient to prevent its crystallization. This constitutes a non-negligible economic advantage that will be appreciated by the person skilled in the art.

The chewing gums obtained according to the invention obtained an excellent note of crusting or crunchy condition, during the tasting by the jury of experts. In addition, the thermodynamic analysis of this crystalline coating according to the invention showed that it had a melting point of 92 ° C.

Claims

CLAIMS 1. A hard crystalline coating containing at least 90% of a polyol mixture consisting of dry for about 20 to 50% mannitol or about 5 to 50% glucose-1,6-mannitol, the missing complement being constituted to 100% of the dry matter of the mixture, basically by a polyol selected from xylitol, mannitol or lactitol. The hard crystalline coating according to claim 1, wherein the polyol mixture represents more than 95% and preferably more than 98% of the coating. The hard crystalline coating according to claim 1 containing mannitol, which represents 20% to 40% dry, preferably 22 to 35% dry matter of the polyol mixture. 4. The hard crystalline coating according to claim 1 which contains glucose-1,6-mannitol, which represents from dry 10% to 40% and preferably 15% to 35% dry matter of the polyol mixture. The hard crystalline coating according to claim 1 which contains pure crystals of mannitol or glucose-1,6-mannitol intimately mixed with pure crystals of xylitol, maltitol or lactitol. 6. The hard crystalline coating according to claim 1 which contains "co-crystals" which are composed on the one hand of mannitol or of glucose-1,6-mannitol and on the other hand of xylitol, maltitol and lactitol. 7. Method for obtaining by hard grageification a hard crystalline coating according to claim 1 comprising the following steps: - putting in rotation rotating nuclei that must be grageified in a grageification turbine; creation to the surface of the cores, of a semicrystalline coating containing at least 90% of a polyol mixture provided by repeated applications of at least one crystallizable liquid composition or at least one liquid crystallizable composition and at least one crystallizable composition.; the polyol mixture being constituted on dry by approximately 20 to 50% mannitol or approximately 5 to 50% glucose-1,6-mannitol, the missing complement being essentially constituted for 100% dry matter by a polyol selected from xylitol , maltitol or lactitol, preferably a drying of the coating, inside or outside the grageification turbine to allow more complete crystallization of mannitol or glucose-1,6-mannitol and at least one of the complementary polyols. 8. The process that improves the speed of grageification and the crunchy state of coatings obtained by hard grageification with the help of a polyol selected from xylitol, maltitol, lactitol and mixtures thereof which consists in replacing: - 20 to 50%, preferably 20 to 40% and more preferably 22 to 35% of the selected polyol, for mannitol, or -5 to 50%, preferably 10 to 40% and more preferably 15 to 35% of the selected polyol, for the glucose-1,6-mannitol. 9. The use of mannitol or glucose-1,6-mannitol as an agent that improves the hard grageification rate with the help of a polyol selected from xylitol, maltitol, lactitol or mixtures thereof, in which mannitol and glucose-1, 6-mannitol represent respectively from 20% to 50% or from 5% to 50% of the polyol. 10. The hard crystalline coating containing at least 90% of a polyol mixture formed in the dry state by approximately 20 to 50% mannitol, and the missing complement being essentially constituted to reach 100% of the dry matter of the mixture by xylitol , characterized in that it has a melting point comprised between 75% and 89% and more preferably between 82 ° C and 89 ° C. 11. The hard crystalline coating containing at least 90% of a polyol mixture formed in dry form by about 5% to 50% glucose-1,6-mannitol, and the missing complement being essentially constituted to reach 100% of the dry matter of the mixture by xylitol, characterized in that it has a melting point comprised between 60 ° C and 80 ° C and more preferably between 62 ° C and 78 ° C. 12. The hard crystalline coating containing at least 90% of a polyol mixture consisting of dry by approximately 20 to 50% mannitol, essentially being the missing complement to reach 100% of the dry matter of the mixture, by xylitol, characterized in that it has an enthalpy of fusion comprised between 130 and 180 J / g »Y and more preferably between 140 and 175 J / g. 13. The hard crystalline coating containing at least 90% of a polyol mixture constituted in dry form by about 5% to 50% glucose-1,6-mannitol, and the missing complement being essentially constituted to reach 100% of the dry matter of the mixture by xylitol, characterized in that it has a melting enthalpy comprised between 130 and 180 J / g, and more preferably between 140 and 175 J / g. 14. Grageized product, characterized in that it has a hard crystalline coating according to any of claims 1 to 6 or 11 to 13 or obtained according to claim 7. 15. The grageified product according to claim 14, characterized in that it consists of a chewing gum .