Abstract
The effects of kefir grains from different regions in China on fermentation and bioactivity were studied by using pH value, acidity degree, protein hydrolysis degree, antioxidant activity, angiotensin converting enzyme (ACE, EC 3.4.15.1) inhibition rate and sensory evaluation as indexes to select the most suitable kefir grains as starter for goat milk. The parameters of kefir fermented goat milk were optimized by single factor experiment constantly. The results showed that kefir grain K1, which performed better in antioxidant activity, ACE inhibitory activity than the other four kefir grains and sensory evaluation was inferior to kefir grain K5 only, was suitable for the fermentation of goat milk. And the optimum fermentation conditions were found to be as 3% inoculation size at 25 °C for 22h.