Effect of Whey Protein Concentrate and Casein Hydrolysate Supplementations on Physicochemical and Sensory Properties of Yogurt

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. 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). For comparison، reconstituted skim milks were made with 11 and 12% total solids as control. Yogurts were prepared with commercial starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) and their fermentation proccess were stopped at pH=4. 6 and samples stored at 4°C up to 21 days. The lowest pH value was obtained when milk base was supplemented with WPC. pH values of all yogurt samples did not change significantly during 21 days of storage and ~0. 18% increase in titratable acidity was observed during storage period. The lowest syneresis was observed in yogurts containing blend of WPC and CH. Moreover، the syneresis values of these yogurts increased slower than other samples during storage. Consistency of fortified yogurts was higher than control yogurt and the consistency values of these samples reduced slower than control sample during 21 days of storage. With regards to total acceptability، the best samples were yogurts supplemented with blend of WPC and CH.