The ability of probiotic lactic acid bacteria to ferment Egyptian broken rice milk and produce rice-based yoghurt

Abstract

Lactic acid bacteria (LAB) contribute to the fermentation of non-dairy cereal products such as rice milk and produce economic products like yoghurt and cheese. These bacteria also have a cytotoxicity activity against cancer cells. The current study intends to use Lactobacillus strains to ferment broken rice milk and produce financial yoghurt products, as well as to assess the growth, physicochemical properties alteration, sensory characteristics, and cytotoxicity of final products. This study indicated that the fermentation of broken rice milk for 8 h by Lactiplantibacillus plantarum ATCC 14917 and milk yoghurt cultures were more favorable than by Lc. casei DSM 20011, and L. acidophilus ATCC20552, which gave high viability (8.9 Log CFU/mL), specific growth rate (0.181, and 0.203 h⁻¹) and doubling time (3.83 and 3.41 h), respectively. Also, they dropped in pH values into ranged from 4.2 to 4.4, and increased in total titratable acidity and the acetic and lactic acids contents (0.82 and1.26 mg/L, respectively). The highest acidification rate (V_max) was 0.006 and 0.007, and pH U/min, the maximum acidification time (T_max) was 4 h and the time to reach pH 4.6 (T_e) was 5 h and 4 h for sample fermented by Lpb. plantarum and milk yoghurt cultures, respectively. Under refrigerated storage at 5 °C, the rice yoghurt seems to get a shelf life of 12 days. The sensory qualities of LAB rice yoghurt were satisfactory, and it was not toxic (safe) on OEC normal cells (IC₅₀ = ranged between 445.9 and 537.9 μg/mL) and cytotoxic on CaCo-2 colon cancer cells (IC₅₀ = ranged between 107.8 and167.8 μg/mL). The yoghurt rice included a lot of vitamin B₆ and B₁, but not much vitamin B₂ or C. As a result, this product is high in nutritional value.