The effect of kefir grain concentration and fermentation duration on characteristics of cow milk-based kefir

Abstract

Cow's milk is very easily damaged because of the content of decomposing bacteria that occurs very quickly, so that the milk becomes inappropriate for consumption. Current technological developments in food sector provide an alternative diversification of milk processing products. One such technology is fermentation of cow's milk into kefir. The method used in this study is a Completely Randomized Design method (CRD) without any repetition. The raw materials used are cow's milk, kefir grains with various concentrations, namely 3%, 5% and 7% per 1L kefir, with different fermentation lenght namely 18 hours, 21 hours and 24 hours. Furthermore, the characteristics of lactic acid levels were tested using alkalimetry method, protein content test using the formol method, and the Lactic Acid Bacteria (LAB) test using Man Rogosa Sharpe (MRS) on growing medium. Characteristic test results show that lactic acid levels are optimal at 5% kefir grain concentration as well as optimal protein levels at 5% kefir grain concentration, while total LAB obtained are 1.80 × 107 cells / mL at 3% kefir grain concentration.