The objective of the research study was to determine the effect of dry matter concentration degree in milk on its souring dynamics as well as on some selected parameters of acid tvorog curd. The research material involved acid curds produced under laboratory conditions from reconstituted milk with different dry matter contents and prepared from skimmed milk powder. A Probat 505 starter culture was added to milk at a temperature of 28 ± 0.5°C and, in order to produce a tvorog curd, the souring process of milk was carried on until its pH value reached 4.60 ± 0.02. Changes in active acidity were continuously recorded. In the milk, the content of dry matter, protein, lactose, and ash were determined, and, additionally, a titratable acidity value was measured in the tvorog curds. Texture characteristics of the experimental curds produced were analysed and a sensory evaluation of those curds was performed. The time of milk souring increased along with the increase in the dry matter content in milk above 13.5 %. The content of dry matter in the raw material impacted the texture profile of curds and, along with the increasing content of dry matter, a significant increase occurred in the compactness, consistence, cohesiveness, and viscosity index of the curds. Also, the concentration of dry matter components highly impacted the development of sensory characteristics of curds. Along with the increase in the dry matter content in the processed milk, the intensity of cream colour, sweet taste, aftertaste of milk powder, and aromatics significantly increased in the curds, while the intensity of the surface uniformity, consistence and colour, acidic taste, acidic smell as well as the purity of those parameters decreased. From a technological point of view, the increase in the dry matter concentration in milk to as high as ca. 18 % makes it possible to produce good quality tvorog curds within an optimal souring time.
milk, dry matter, souring dynamics, tvorog curd, texture characteristics, sensory properties