Fermented milk concentrates structural and mechanical characteristics comparison

The purpose of the study is a comparative assessment of the composition and ability to rennet-induced coagulation of pasteurized raw milk, as well as its concentrates obtained by ultrafiltration (UV retentate) and traditional vacuum evaporation (HV concentrate). Objectives: to establish the influence of the concentration technology and the peculiarities of the composition of the obtained concentrates on the change in the mechanism of the coagulation process. Objects of the study: raw milk classified as class I in terms of cheese suitability; UV retentate with a volume concentration factor of 3.5; BB-concentrate with a degree of thickening of 1.7 in terms of dry matter; milk-clotting preparations - chymosin (X) and pepsin (P) with an activity of 100 thousand c.u. A comparative analysis of the kinetics of gelation was carried out using the method of rotational viscometry, and the quality of model rennet clots produced from skimmed milk, its UV retentate and BB concentrate was studied by exposure to an equivalent amount of various milk-clotting agents: chymosin and pepsin. The results of the experiment showed that the UV treatment method causes a high kinetics of retentate gelation and the ability to form the densest clots in relation to the original milk, while BB concentrates, on the contrary, demonstrate a low coagulation ability: a weak structure of coagulates and an increased duration of all periods of rennet coagulation. The most effective way to concentrate milk in order to obtain strong rennet-induced milk gels is its ultrafiltration, and the use of explosive concentrates in dairy production has certain prospects for the development of products characterized by a soft consistency and high moisture content of clots.