Research noteFermentation conditions of walnut milk beverage inoculated with kefir grains

The aim of the present study was to evaluate the use of kefir grains as inoculum for the preparation of walnut milk beverage. The results showed that the single factor effect of fermentation time, fermentation temperature and sucrose concentration on walnut milk beverage fermentation was very significant (P = 0.01), and the single factor effect of inoculum size was significant (P = 0.05). The suggested optimum fermentation conditions are the following: fermentation temperature of 30 °C, fermentation time of 12 h, inoculum size of 3 g of kefir grains (wet weight) and sucrose concentration of 8 g/100 mL. Under the optimum fermentation conditions, the sensory evaluation score of the beverage reached its maximum value of 88, and the pH and titratable acidity of the beverage were respectively 4.16 and 72 °T. The viable cell counts of lactococci, lactobacilli and yeast surviving in the beverage were 8.2 × 107, 1.1 × 108 and 1.0 × 106 CFU/mL respectively.

► The use of kefir grains as inoculum for preparation of walnut beverage was evaluated. ► Effect of several factors on quality characteristics of walnut beverage was studied. ► Kefir grains are proved to be efficient inoculum for preparation of walnut beverage. ► The optimal fermentation condition of walnut beverage was determined. ► Chemical, microbial and sensory characteristics of walnut beverage were investigated.