Ermolaev V. A, Komarova N.A., Sosnina O.B.

The Kemerovo technological institute of the food industry

Changes of a microstructure of products of an animal origin in the course of freezing

Freezing of a product is the most widespread method of conservation of a product, and also the integral stage in many technological operations applied in the food-processing industry at which in fabrics of a product there are the essential physical and chemical changes reflected finally on its quality. Thus distinguish the freezing occurring in separate freezing chambers and self-freezing, occurring under vacuum as a result of tap of warmth by evaporation at fall of temperature more low криоскопической points and formations in a product of crystals of ice. Process of self-freezing under vacuum is caused by intensive evaporation of a moisture in a product.

For the majority of materials the most comprehensible is the method of self-freezing that is caused by more uniform and fast cooling of a product on all volume. Such a frost allows to avoid formation of large crystals of the ice adversely operating on structure of fabrics of a product. Thus self-freezing is favourable in the power plan.

Firm cheeses on power and food value take a special place among foodstuff that is caused by the high maintenance in them of fibers, dairy fat, vitamins and mineral salts. Cheeses are a source of irreplaceable amino acids [1]. For research of influence on a microstructure of cheese of freezing and self-freezing in vacuum cheese "Dutch" was used. Preliminary a frost of cheese it was made in the refrigerating chamber at temperature -40OC. Self-freezing was carried out in the vacuum chamber.

a

d

b

e

c

f

Fig. 1. A microstructure of the "Dutch" cheese: a, d - before frosts; b, e - after self-frosts under vacuum; c, f - after frosts in the freezing chamber

On fig. 1 cheese microphotos "Dutch" before and after frosts are presented. After self-freezing cheese was characterized by an equal, smooth surface (fig. 1 b, e) with characteristic cellular structure and capillaries, the size 100 microns.

Formation of crystals of ice in the course of self-freezing occurs by gradual deepening of a zone of crystallization. A sign of end of process of self-freezing is achievement in the middle of cheese particles of temperature-20 …-30OC. Duration of self-freezing varies within 20-30 minutes. Increase of duration of this process conducts to formation of too large crystals of ice that can be at the bottom of destruction of cages of fabrics and deterioration of quality indicators of the defrosted cheese.

At fast freezing more uniform formation кристалликов ice in cages and in intercellular space is observed. In a case with slow freezing are formed кристаллики the large sizes, the cheese structure is thus broken, the surface becomes rough with chaotic сколами (fig. 1 c, f). The difference in distribution of crystals of ice at fast and slow freezing speaks diffusion processes.

Thus, on the basis of the spent experimental researches the expediency of application of self-freezing under vacuum at which more uniform structure with small crystals of ice in comparison with заморозкой in the freezing chamber is observed has been established that directly affects quality of cheese.

 

The list of references:

1. Majors, A.A. Formation of structurally-mechanical properties of cheese / А.А. Majors, Е.А. Nikolaev. – Barnaul, 2005. – 223 P.