Growth, proteolytic, and ACE-I activities of Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus and rheological properties of low-fat yogurt as influenced by the addition of Raftiline HP.

This study investigated the influence of incorporating Raftiline HP on the pH, growth, proteolytic, and angiotensin-I converting enzyme inhibitory activities and on spontaneous whey separation, firmness, and rheological properties of low-fat yogurts during storage for 28 d at 4 degrees C. Three types of yogurts were prepared from skim milk containing 0% (YI0, control), 2% (YI2), and 3% (YI3) Raftiline HP, respectively. The incorporation of Raftiline HP improved the growth of starter organisms, particularly that of Lactobacillus delbrueckii ssp. bulgaricus, resulting in shorter fermentation time. There was a significant improvement in total proteolysis, which was highest in yogurt containing 3% Raftiline HP. The ACE inhibitory activity was maximal in YI3 compared to YI2 and YI0. Incorporation of Raftiline HP did not affect whey separation and firmness of the low-fat yogurts. All these products were more fluid like with distinct pseudoplastic properties and lesser ability to resist deformation upon applied shear.