Production and evaluation of microbiological & rheological characteristics of kefir beverages made from nuts

Herein we report the preparation of nut milks followed by kefir production from Almond, peanut, hazelnut, walnut, and cashew. Nut-based milks were used to make kefir from 100% vegetable milk without food additives or sugar. During 30 days of storage at 4 °C, the microbiological (total aerobic mesophilic bacteria, lactobacilli, lactococci, acetic acid bacteria, yeast) and rheological (apparent viscosity, consistency constant, flow behavior index, thixotropy) parameters of kefir samples made from cow's milk and nut-based milk were monitored and compared to examine the effects of different milk types and storage time. The titratable acidity value of nut kefirs was lower than cow kefir. Kefir from walnut milk had the lowest titratable acidity value (0.15%), lowest apparent viscosity (3.3 mPa.s) and consistency coefficient (682.1 mPa.sn). Titratable acidity values of the samples increased while apparent viscosity, thixotropy, flow behavior index and consistency coefficient decreased during storage. According to the power-law model, the kefir samples exhibited non-Newtonian pseudoplastic flow behavior. The apparent viscosity values of peanut and almond kefirs were higher among the prepared samples (p < 0.05). The total number of aerobic mesophilic, lactic acid and acetic acid bacteria of kefir samples decreased during storage, while the number of yeasts increased. Kefir made from cow's milk had the highest average total aerobic mesophilic bacteria, lactococci, lactobacilli, and acetic acid bacteria counts, whereas kefir made from peanut milk had the highest yeast count (p < 0.05). During storage the lowest decrease (%) in the counts of microorganism was determined in almond kefir (4.06%), followed by cow (5.16%), walnut (5.73%), peanut (6.72%), cashew (7.78%), and hazelnut kefirs (9.53%).