Effect of WPC and Casein Hydrolysate Supplementations on Physicochemical and Sensory Properties of Bioyogurt

The aim of this research was to study the effects of whey protein concentrate (WPC) and casein hydrolysate (CH) on chemical (pH and titratable acidity)، physical (consistency and syneresis) and sensory properties of yogurt containing probiotic bacteria. Reconstituted skim milk at 10% total solids was fortified with 1 and 2% of WPC، CH and blend of them (WPC to CH ratios of 1:1). Reconstituted skim milks were made with 11 and 12% total solids as control. Bioyogurts were prepared with commercial probiotic starter culture (Lactobacillus acidophilus، Bifidobacterium sp.، Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus). Fermentation was stopped at pH=4. 6 and samples stored at 4°C for 21 days. Addition of WPC resulted in the highest pH value and the lowest titratable acidity. Acidity values of supplemented bioyogurt samples increased between 0. 12 - 0. 19% during 21 days of storage. Mَoreovere syneresis of these yogurts was lower and their consistency was higher than control. Bioyogurts containing WPC had the lowest syneresis and samples containing CH or WPC had the highest consistency. With regards to total acceptability، the best samples were bioyogurts supplemented with WPC and blend of WPC and CH.