Study of Antioxidant Activity, Peptides, and Chemical Quality of Goat Milk Kefir on the Different Post-Acidification Periods During Cold Storage

Abstract

The interaction between raw goat milk, lactic acid bacteria (LAB), and kefir grain resulted in the unique taste and flavor of fermented products. Under optimum temperature, LAB and yeast had the better condition for growth and optimizing metabolic activity. The proportion level of kefir grains should be considered during the incubation period because it could change the logarithmic growth phase of lactic acid bacteria. After the processing, cold storage should be applied to suppress microorganism growth in the post-acidification period. The prolonged post-acidification period potentially affects the quality of Goat milk kefir products. This research aimed to evaluate the effect of a post-acidification period during cold storage based on antioxidant, peptides, and chemical quality of goat milk kefir. The experimental design was a completely randomized design (RCD) with four treatments and three replications. The quality analysis was done in the different post-acidification periods for 1 day, 7 days, 14 days, and 21 days after being stored at 4 o C. Duncan Multiple Range Test (DMRT) was used for further statistical analysis. The results showed that the different post-acidification periods had significant effects (p<0.05) on antioxidant activity, peptide, fat, and ethanol content. On Average, antioxidant activity, peptide, fat, and ethanol content in goat-milk kefir were 55.70 ± 2.25 %, 9.32 ± 0.13 mg / ml, 1.86 ± 0.08%, and 1.04 ± 0.04%, respectively. In conclusion, the longer period of post-acidification has a major contribution to the change of goat milk kefir characteristics during cold storage.