Abstract

Ryazhenka is a popular Russian baked milk product. The physicochemical profiles of commercial, small-farm, and home-made baked milk remain fragmentary in scientific literature. This article describes the efficiency of various approaches to milk fermentation control and introduces a new experimental baked milk formulation.
The study involved commercial samples of fermented baked milk and experimental samples obtained from local ultra-pasteurized milk and the Vita starter. After heating, the milk samples were mixed with the starter culture and fermented at 37°C until stable titratable acidity. The physicochemical tests relied on standard methods used in industrial practice.
After the fermentation, the freezing point dropped to –0.691°C and the pH went down to 4.48 whereas the titratable acidity and the specific conductivity rose to 89.0°T and 7.23 mS/cm, respectively. The dynamics of changes in all parameters during cultivation included periods of constant values (3–4 h) followed by a sharp increase/decrease and a slow change until the end of fermentation. The freezing point, titratable acidity, specific electrical conductivity, and pH of the experimental products were compatible to the commercial samples. The acidity changes during fermentation were similar to the data reported by other authors.
The research yielded an extended set of physicochemical parameters for the ultra-pasteurized milk and baked milk samples available from retail shops, Minsk, Belarus, and those developed in laboratory conditions. It revealed a linear dependency between the freezing point, acidity, and specific electrical conductivity during cultivation. The data obtained may help factory laboratories to optimize various quality control methods.

Keywords

Starter culture, fermented baked milk (ryazhenka), freezing point, titratable acidity, active acidity, electrical conductivity, water activity

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