Effect of Temperature‐Controlled Microwave Drying on the Physicochemical and Microbiological Properties of Kefir Powder

Abstract

In this study, the physicochemical and microbiological properties of kefir powders produced using a drying system modified by microwave temperature‐control (MTCM) and foam‐mat drying (FMD) were evaluated. The color parameters ( L , a , and b ) of the kefir powders ranged between 89.68–91.16, −1.54–(−4.48), and 14.24–15.64, respectively, while Carr Index (CI) and Hausner Ratio (HR) values varied from 39.39 to 63.20 and 0.93 to 1.13. Titration acidity (TA) values of kefir powders ranged from 4.00% to 4.46% and showed a general decreasing trend with increasing drying temperature and egg white concentration ( p  < 0.05). Water solubility index (WSI) values varied between 41.44% and 45.89% and decreased significantly as drying temperature increased, with a more pronounced reduction observed in samples containing 2% egg white. Hygroscopicity values ranged from 11.81% to 13.28% and increased with higher egg white concentration, while higher drying temperatures resulted in lower hygroscopicity. Water activity values remained within a range associated with enhanced shelf stability. Microbiological analyses revealed a substantial reduction in yeast counts following drying, whereas Lactobacilli and Lactococci were not detected in the kefir powder samples. Overall, the physicochemical and microbiological properties of kefir powders were significantly influenced by both drying temperature and egg white concentration.