The present invention relates to a fine sugar product obtained by comminuting sucrose or a sucrose- containing mixture to a mean particle size of 5 to 25 μm, a process for its production by counterjet milling and classification, and its use in icings, in the con¬ fectionery industry, specifically in chocolates, and as seed crystals in the sugar industry. The invention also relates to products prepared using this fine sugar product.

In many applications of sugar, the sugar must be very fine and also have a very uniform particle size. It is required of many ingested sweet products, such as chocolate, that organoleptically they have a velvet- smooth mouth feel. This calls for a very small particle size of the sugar and other solid ingredients in said products. Thus, for example in finished chocolate the proportion of sugar grains having a size exceeding 30 μm must be below 5% in order for the chocolate not to appear coarse to the tongue. This also applies to fon¬ dants employed for instance as coatings on bakery products and biscuit products (such as icings for iced doughnuts and gingerbread) and in confectionery fill- ings.

Sugar having a grain size in the range 10 μm - 1 mm can be used to prepare chocolate when the produc¬ tion process is selected in accordance with the grain size. If the chocolate is produced by a process com- prising mixing, rolling and conching of the in¬ gredients, one rolling step, i.e. roll refining, is sufficient if the particle size of the sugar is less than 200 μm. In order for it to be possible to entire¬ ly omit the refining, the particle size of the sugar must be less than about 20 μm. In another chocolate

process that is commonly used, a crumb-like prefabri¬ cate is prepared from part of the ingredients by heat¬ ing them in the presence of water and evaporating the water; this prefabricate is called the crumb (cf. e.g. inifie, B.W., Chocolate, Cocoa and Confectionery: Science and Technology, Second edition, AVI Publishing Company, Inc., Westport, pp. 108-113). The crumb is mixed with the other chocolate ingredients, refined, and conched. Also in this case the refining may be omitted, if the crumb is comminuted to sufficient fine¬ ness prior to the addition of the other ingredients.

Fondants may be either wet fondants or dry fon¬ dants. Wet fondants comprise two phases: a solid phase formed by fine sugar and a syrup forming a liquid phase and comprising sugar solids in high concentration. Wet fondants are produced either by cooling crystallization of the product into paste form or by adding the neces¬ sary liquid phase to a dry fondant. The production of fondant and the problems associated with the storage of wet fondant have been discussed for instance in Lees, L. & Jackson, E.B., Sugar Confectionery and Chocolate Manufacture, Leonard Hill, 1973, in the section Fon¬ dants, Creams and Crystallized Confectionery (pp. 211- 215). Storage problems are avoided by using dry fon- dants wherefrom a wet fondant may be prepared if desired, as stated previously. The conventional dry fondants comprise very fine sugar whereto a small amount of a polysaccharide doctoring/controlling the crystallization, and possibly also fat, has been added. By the conventional grinding methods it is in fact possible to prepare from sucrose a ground product having a sufficiently small particle size and narrow size distribution for use in chocolate production with¬ out roller refining and for the production of fondants. However, the amount of the product having sufficient

fineness obtained by these grinding methods is rather small and its recovery by classification is disad¬ vantageous. An example of the particle size distribu¬ tion of a typical commercial icing sugar is curve 1 shown in Figure 2. It is to be seen from the curve that said product, having a mean particle size of 28 μm, comprises about 30% by volume of particles having a size of 40 μm or larger. Commercially are also avail¬ able fine sucrose grades suitable for the production of fondants. The quality of these, however, is inadequate; the drawback is often non-uniform particle size dis¬ tribution. Curve 2 in Figure 2 illustrates the particle size distribution of a product available under the trade name Fondant icing (manufacturer Tate & Lyle Pub- lie Limited Company, London).

In addition to the above drawbacks, very fine sucrose produced by the conventional grinding methods is attended by decided disadvantages resulting from the fact that when crystalline sucrose is crushed into a very small particle size, it changes largely into amor¬ phous form, which is an unstable state. Small sucrose particles in this form very strongly absorb flavours from all materials (e.g. the grinding machinery, air) with which they come into contact. Further, they have a strong tendency to adhere to each other, which res¬ ults in clodding of the product. Absorption of flavours produces an off-flavour in the product: in a fine prod¬ uct of this kind, an unpleasant, often metallic and/or stale flavour is present. This off-flavour is often masked by using flavour-improving additives (which for instance in fondants may simultaneously be dyes); to some extent, however, it restricts the use of the prod¬ uct. On account of the clodding tendency, additives preventing clodding must usually be provided in such fine products.

A solid dry material can be ground to a very fine particle size in a counterjet mill wherein the particles to be comminuted that are fluidized in a car¬ rier gas, typically air, are conveyed so as to collide with one another at a high speed. Advantageously, a classifier wherein the ground material is classified into fractions of varying particle sizes is provided in connection with the mill. Such apparatus and processes have been disclosed in several patent publications, for instance in Finnish Patents 62 235, 72 896, 72 897, 74 222, 77 580, 77 168 and 80 617, and they have been implemented mainly to industrial minerals and pigments that are difficult to grind. Finnish Patent Application 883405 discloses the comminution of cereal flour in a counterjet mill and classifier. Finnish Patent 85 145 disclosed the comminution of a crystalline sweetener, sucralose, in a jet mill to a maximum mean particle size of 10 μm, the largest particle size being not more than twice the mean particle size. The significance of grinding has been dealt with in Eynck, V., "Dry Mixing System in Manufacture of Confectioner Coating", The Manufacturing Confectioner, October 1986, pp. 57-59.

Oy Finnpulva Ab has developed fine-grinding apparatus and technology, which according to Oy Finn- pulva Ab's brochure "FINE, FINER, FINNPULVA ^R " are suit¬ able for producing fine powders for the construction material, chemical, mining and extractive, food, fodder and pharmaceutical industry and biotechnology. Applying said technology, tests were started for the fine grind- ing of sucrose on industrial scale. Dried, and respect¬ ively cooled, compressed air was employed as the car¬ rier gas. In that connection, very difficult problems were presented by clodding and vaulting of the sucrose, and the method was not suitable for industrial produc- tion. Furthermore, the ground product had the above-

described off-flavour typical of fine sucrose ground by the conventional methods.

In the initial tests, clodding very rapidly caused blockage of the apparatus, wherefore changes were made in the apparatus to optimize it for the grinding of sucrose. It was further found that the grinding parameters which had been given by the manu¬ facturer and which had been suitable for other mater¬ ials ground by this technique were not suitable for the grinding of sugar, but a change of the crystalline suc¬ rose used as the raw material into amorphous state took place during the milling, which was largely the reason for said clodding problems and off-flavour.

In further tests it was found that by suitable regulation of the temperature and pressure of the air employed as a carrier gas in the milling, clodding of the product could be avoided, and the off-flavour was also considerably less or there was no off-flavour. When heated air is used as a carrier gas instead of cooled air, the amorphous state of sucrose is cancelled by the effect of heat, and thus the reformed crystal¬ line state remains readily flowable and does not absorb flavours. The change of amorphous sucrose into crystal¬ line sucrose could also be improved by post-treating the ground sucrose hot, for instance in a screw mixer.

Furthermore, it was found that the problem of clodding and vaulting could be avoided or remarkably diminished and the production capacity of the mill in- cresed by adding native starch, dried starch syrup or hydrolysed starch to the sugar to be ground.

The object of the present invention is to pro¬ vide a fine sugar product having a particle size and particle size distribution suitable for use in the pro¬ duction of chocolate and fondants without additional refining, and being simple and cost-effective to pro-

duce. It is a further object of the invention to pro¬ vide such a fine sugar product which has markedly bet¬ ter flavour characteristics than the previously available ground sugar products, and wherewith the use of chemical anti-clodding agents such as tricalcium phosphate can be eliminated totally or in part.

These objects are achieved with the substanti¬ ally dry, substantially free-flowing fine product of the invention comprising sucrose or a sucrose-contain- ing mixture, being characterized in that it is prepared by grinding the crystalline sucrose or mixture contain¬ ing crystalline sucrose substantially autogenously in a counterjet mill employing as a carrier gas air the pressure and temperature of which are regulated to minimize formation of amorphous sucrose, and classify¬ ing the ground product to a mean particle size of 5-25 μm.

The invention also relates to a process for pro¬ ducing the above fine product, being characterized in that the crystalline sucrose or substantially dry granular mixture containing crystalline sucrose is ground substantially autogenously in a counterjet mill employing as a carrier gas air the pressure and temper¬ ature of which are regulated to minimize formation of amorphous sucrose, and the ground product is classified to give a product having a mean particle size of 5-25 μm.

With air heated to 40-120°C as the carrier gas, sucrose has been found to remain substantially in crys- talline state.

The particle size distribution of the fine suc¬ rose or sucrose-containing mixture produced in accord¬ ance with the invention as determined by the PMT - PAMAS method is advantageously in the range defined by curves A and B in Figure 1. When the mean particle size

is 5 μm, preferably a maximum of 50% of the particles have a size below 5 μm and a maximum of 20% above 10 μm. When the mean particle size is 25 μm, preferably a maximum of 15% of the particles have a size below 10 μm and a maximum of 20% above 40 μm.

The ground product is preferably divided in the classifier into two fractions, the coarser of which can be recycled into the mill or used as such for a suit¬ able purpose. The product according to the invention, having a mean particle size of 5-25 μm, is recovered as the finer fraction.

When crystalline sucrose was ground by the pro¬ cess of the invention, a product with a particle size distribution as shown in curve 3 in Figure 2 was obtained.

In a preferred embodiment of the invention, sugar is ground in admixture with native starch, dried starch syrup or starch hydrolysate. These are ingredi¬ ents often mixed with fine sugar to prepare traditional fondants. Thus, an extra mixing step of fine materials can be avoided when these ingredients are ground con¬ currently with crystalline sucrose.

Native starch effectively diminishes the clodd¬ ing and vaulting problems and increases the production capacity of the mill when used in amounts of from 2 to

10%, preferably about 3 to 4% by weight of the mixture.

With the process of the invention, a dry fondant can also be advantageously prepared by concurrent grinding of crystalline sucrose and dried starch syrup or hydrolysed starch, such as maltodextrin, having a dextrose equivalent in excess of 10, preferably 20 to

40. The proportion of dried starch syrup or hydrolysed starch in such a dry fondant can be for example 5-15%.

Preferred embodiments of the invention include dry fondants having e.g. the following basic composi-

tion:

1) sucrose 90-92% dried starch syrup, DE 28-36 8-10% 2) sucrose 90-94% crystalline fructose 3-5% crystalline glucose anhydride 3-5%

A wet fondant can be prepared from the dry fon- dant of the invention simply by mixing the dry fondant in a suitable liquid portion.

The process of the invention is also suitable for grinding a crumb employed in chocolate production, the fine premix obtained being useful for chocolate production without roll refining.

The most preferred temperature of air employed as a carrier gas in the grinding is dependent on the material to be ground. In the grinding of sucrose, the temperature of the carrier gas is preferably 50-100°C. If the material to be ground contains fructose, the temperature is preferably 50-80°C.

The pressure of the carrier gas employed in the process of the invention is selected to be suitable for the construction of the mill employed and the material to be ground in each case. It can vary for instance in the range 1.5-5 bar. For sucrose, a pressure of about 2-4.5 bar has been found preferable.

The fine sugar product prepared in accordance with the invention is suitable for the production of chocolate and icings without roll refining. It can also be used in the production of chewing-gums, e.g. dusting gum sticks, and fillings, e.g. fillings for chocolate and truffles. Further, a wet fondant can be prepared therefrom and used for various fillings and coatings in bakery products, particularly biscuits, Danish pas-

tries, cakes and doughnuts. The fine sucrose ground in accordance with the invention is also suitable for use as seed crystals in the sugar industry and in the pro¬ duction of confectionery. The process of the invention can be carried out as a continuous process. It also enables for instance in chocolate production a continuous, integrated pro¬ cess from the grinding of the starting materials right down to the forming of the final product, since no rolling steps are needed.

The following advantages, for example, are achieved with the process of the invention: by means of the grinding parameters, the need for anti-clodding agents can be minimized, - the particle size can be easily controlled, so that the organoleptic feel of the product is agreeably smooth, the grinding is substantially autogenous, that is, the material to be comminuted will only come into contact with foreign materials to a very small degree and thus contamination will remain low, the air employed as a carrier gas can be regu¬ lated to be specifically suited to the product, the product obtained is pure in taste and colour.

The invention will be illustrated in greater detail by means of the following examples, which are not intended to restrict the scope of the invention.

Example 1 Grinding of sucrose

A) Sucrose was ground using as raw materials crys¬ talline products having mean particle sizes of 0.33±0.03 mm and 0.50±0.05 mm. The sucrose was ground and classified in a counterjet mill FP4 and a dynamic rotor classifier FPC20R manufactured by Oy Finnpulva

Ab, in which improvements had been made to optimize them for grinding of sucrose. The crystalline sucrose employed as the raw material was fluidized in carrier air in a pressurized chamber, and the fluidized mixture obtained was accelerated in mill jets wherefrom it was conveyed to a milling chamber. The temperature of the carrier gas in the fluidizing and acceleration steps was about 80°C, the feed pressure about 4 bar. B) The sucrose grinding tests were continued fol- lowing the process as outlined in item A, except that the temperature of the carrier gas was about 60°C and the feed pressure to be used in each test was selected from the range 4-5 bar.

The particle size distribution of the sucrose powder thus obtained, as defined by the PMT - PAMAS method, is shown by curve 3 in Figure 2. The sucrose powder obtained was readily flowable, and no clodding problems were encountered in the grinding and clas¬ sification. The product had a pure sugar taste. Example 2

Dry fondant

A mixture of crystalline sucrose and dried starch syrup (starch hydrolysate having a dextrose equivalent of 36-39, dry solids content >94%) co pris- ing 90% of sucrose and 10% of dried starch syrup, was ground following the process as outlined in Example 1. The temperature of the carrier gas in the fluidizing and acceleration steps was 80°C and the feed pressure 5 bar. The coarse fraction obtained from the classifier was returned to the mill; the recycling load was twice the feed.

To optimize the flow of the product, different dry fondants were prepared using different starch hydrolysates and different mixture ratios. The mouth feel and taste of the resultant products was better

than with the commercially available product.

Example 3

Truffle

Truffle is prepared employing the following in- gredients:

Dry fondant of the invention 32.0% Water 4.0%

Dark or milk chocolate 54.5% Butter 9.0% Lecithin 0.5%

The dry fondant and water are stirred together for example in a Hobart mixer, and the melted chocolate and butter at 35-40°C and lecithin are added into the mixer. The mixture is whipped to have a suitable fluffy consistency and spread for example on baking paper coated with cocoa powder, or extruded into moulds with a pastry bag. The mixture is allowed to crystallize for 1-2 hours. Flavour variation is achieved by adding for ins¬ tance nuts, raisins, dried fruit and/or rum or liqueur aromas.