Machine Processing of Milk in Dairy Production

For fermented milk products, consistency plays a leading role: it provides a quality product and shapes consumer demand. There have been numerous studies of the effect of the technological process on the properties of sour cream, kefir, etc. However, these studies were performed after the introduction of ferment. Thus, the effect of parameters of thermal and mechanical treatment during the primary stage on the physical and mechanical properties of fermented milk products remains understudied. The research objective was to confirm the following hypothesis: the parameters of homogenization during the primary stage affect the consistency of the fermented milk products. A set of experiments made it possible to expose the dependence of the rheologic properties of sourmilk products from the regime parameters of homogenization. The research featured initial mix for kefir and sour cream production. The milk was preheated to 45°C in an Alfa-Laval pasteurizer and separated in an Alfa-Laval separator. The fat-free milk (1% of fat for kefir production) was heated in a pasteurizer to 55–60°C and homogenized at 8–16 mPa. The homogenizing device of the manometer was additionally equipped with a phase separator delimiter of the S-homogenizer type. The acidity and viscidity for the sour cream and kefir were measured at different pressure values. The power expenses on homogenization depended on the pressure and the volume of milk. The pressure of homogenization proved to be a meaningful factor and affected the fermentation process. It rendered a substantial influence on the consistency and taste qualities of the fermented milk product. The experiment defined the optimal temperature of fermentation for kefir production. The optimization of pressure decreased the energy consumptions by 4.4 kW/h (24.4%) per ton. Solar thermal collectors were used to preheat the milk before homogenization, which decreased the specific energy consumption by 10.5 kW/h per ton. The new parameters lower the prime cost of the dairy products and raise their competitiveness.