Impact of Various Fermentation Treatments on Nutritional, Anti-Nutritional and Bioactive Compounds of Black Rice

The black rice flour was subjected to a comprehensive fermentation process, incorporating a diverse range of microorganisms and treatment methodologies. Specifically, the fermentation process utilized two distinct strains of Lactobacillus, namely Lactobacillus brevis (BF) and Lactobacillus plantarum (PF), and yeast Saccharomyces cerevisiae L (YF). Additionally, the fermentation process also involved the use of yeast in conjunction with ammonium sulphate, a fermentation enhancer (YAF), and a combined treatment (CF) of yeast and Lactobacillus brevis. The fermentation process was conducted over a range of multiple time points (12, 24 and 36 hr), to assess the impact of varying fermentation durations on the various parameters of the black rice flour. The fermented samples were then dried and analyzed for their nutritional content, anti-nutritional properties, mineral contents and bioactive compounds. Crude protein and ash content were elevated significantly (p≤0.05) i.e. from 10.29 to 16.59% and 1.49 to 2.67% , respectively following fermentation, however, resulted in a significant reduction of crude fat (77.35%) and crude fibre (61.11%) content. A significant elevation in total phenolic (8.16 to 10.73 mg GAE/g) and flavonoid content (125.51 to 187.21 mg RE/100g) was observed throughout fermentation treatments, resulting in enhanced antioxidant activity (28.91%). The fermentation process also enhanced the nutritional value of black rice flour, reducing anti-nutrients like phytic acid (65.65%) and tannins (50.47%) and boosting mineral levels, particularly copper, iron, zinc and manganese. Although all fermentation treatments enhanced the nutritional and bioactive potential of black rice, but the effect of fermentation with Lactobacillus brevis was highest in improving the nutritional and bioactive components and decreasing the anti-nutritional compounds of black rice. This study suggests that fermentation is a highly valuable technique to elevate the nutritional value, bioactive components and antioxidant activity of black rice flour while reducing the anti-nutrients.