The effect of combined dairy basis on the formation of structure and quality indicators of yogurt
The article deals with the technology of a fermented milk product on the basis of secondary raw milk concentrates. Nanofiltration buttermilk concentrates and whey concentrates with mass fraction of dry substances from 10 to 20 % were investigated. Good organoleptic properties and high protein content (up to 9.3% in buttermilk concentrate and up to 3% in whey concentrate) allowed to choose the concentrate with 20% mass fraction of dry substances for further studies. On its basis the samples of combined dairy basis with different ratios of concentrate buttermilk to whey concentrate (25:75; 50:50; 75:25) were made, and the process of fermentation of YoFlex<sup>®</sup> thermophilic yogurt culture samples was analyzed. The structural and mechanical characteristics of obtained clusters and their water-holding capacity are investigated. Full factorial experiment proved that, in the selected range of factor values, effective viscosity, water-holding capacity, and consistency of the product were strongly influenced by mass fraction of buttermilk concentrate (correlation coefficients are 0.95; 0.93 and 0.94, respectively), and they did not depend on the dosage of starter culture greatly. The analysis of response surfaces and their cross-sections showed that rational values of the mass fraction of buttermilk concentrate are 50 and 75%, the dosage of starter culture - 3 and 5 %.