Preparation and characterization of an apple juice and whey based novel beverage fermented using kefir grains

Abstract

An apple juice and whey based novel beverage fermented using kefir grains was prepared. Effects of the kefir grain amount (2-8%, w/v) and fermentation temperature (20-30°C) on beverage properties were investigated using response surface methodology (RSM). An increase in the kefir grain amount was associated with high acidity, an increased kefiran concentration, an increased lactic acid amount, increased viscosity, a higher lactobacilli population, and a higher yeast population. No definitive temperature results were obtained. Most previous reports used a temperature of 25°C to achieve best results. Use of RSM allowed determination of the most suitable conditions of a 3.73% (w/v) kefir grain inoculum at a temperature of 24.32°C to achieve the highest overall acceptability score of 3.54 in a range of 1-5 for a fermented beverage based on apple juice and whey.