Crystal formation

The size of crystals of ice is very important for creation smooth, cream product and sensation of freshness for the frozen desserts. Small crystals of ice provide smooth structure and cream of the product. Larger crystals are desirable by manufacture fresh, with more intensive taste Italian sherbet.

   At occurrence of crystals of ice it is possible to allocate two stages. At an initial stage there is an origin of the crystals, further the arisen crystals start to be increased. Initial origin of crystals begins at cooling and mechanical influence on a mix. It means, that formation of new crystals occurs only in freezer, but never - in time temper and storages. Very cold cylinder freezer with temperature of a surface of-20--25 degrees is ideal for formation of crystals. Rotating knifes carry out very important role: they cut increasing crystals from a surface of the cylinder. Thus it is necessary to take into account, that only very sharp knifes can provide the minimal size of crystals.

   The freezing point of a mix makes not 0 degrees as for water, and depends on a kind of sugar and the salt, used in mixes and from their concentration. The freezing point is reduced, and the received temperature of freezing refers to as depression of a freezing point. In a mix for ice cream taking place transformation of water into crystals of ice means concentration of firm substances in the stayed water that, thus, conducts to decrease of a freezing point. In summary it is possible to tell, that the most important technological moments by manufacture of ice-cream in freezer are formation and quantity of crystals of ice, and also parallel proceeding process of decrease of a freezing point.

   For standard ice cream from 10 % of fat, 16 % of sugar and 37 % of the common dry weight the parity between crystals of ice and a liquid phase can be expressed as follows depending on temperature (fig. 4).

   On the basis of diagrams which I shall show to you, it is possible to notice, that at a freezing point of 29 % of water of-3,5 degrees are in crystallical form, at temperature of-6,5 degrees already 58 % of water - is frozen. It means, that at temperature of freezing of-6,5 degrees in comparison with - 3,5 degrees form double quantity of crystals of ice. This high quantity of crystals of ice dispersion in the stayed water, which at this moment has high concentration of sugar, proteins and the stabilizer. Consequence of it is that fact, that ice cream obtains high viscosity and leaves from freezer richer. Mechanical loadings and internal friction in a mix of ice cream, which contains high number of crystals of ice, during an output from freezer, are very great. It renders positive influence for the size air bubbles and in any case on hardening of fat.

   Beating ice cream

   Presence of air in a mix of ice cream makes by its softer and softens its cold taste. Isolation effect affects and fusion of ice cream.

   Quantity of air in ice cream designates the term "fluff". Under fluff understand increase of volume. After air was included in a mix of ice cream, 100 % fluff designates, on 1 part of a mix of ice cream it is necessary one part of air (volume to volume).

   Air is brought in a mix before it will get in the cylinder freezer. Uniform distribution air bubbles is reached however only at mechanical influence and physical processing in freezer.

   The size of bubbles and an opportunity of beating depend not only on processing in freezer, but also from a kind and quality of components. There is no doubt that proteins play the big role at beating. Fats, which are, mostly, as liquid fraction, can render negative influence on process of beating.

   It is the best way to supervise fluff during process of freezing in freezer on a consistence of leaving ice cream.

   At good fluff ice cream very much homogeny and fluff has constant quality, and thus the level fluff 150 % is easily achieved. At non-uniform quality of ice cream leaving from freezer it is possible to talk about bad fluff, connected with destruction air bubbles.

   Sometimes it is impossible to achieve the greater fluff, than 70-80 %. When fluff is bad, it is recommended to lower quantity of submitted air and to establish the appropriate system pressure in the cylinder.

   Freezer with preerator gives ice cream with finnier air bubbles that provides reception of softer product. For the benefit of use such freezer speaks also that fact, that in it more optimum foamy structure, stability and cream the ice cream frozen in the form eskimo on a stick.