Physicochemical and functional properties of yeast fermented brown rice flour.

Abstract

In the current study, effects of fermentation on physicochemical and functional properties of brown rice flour (BRF) were investigated. Fermentation conditions were optimized using response surface methodology to achieve moderate acidity (pH5-6), specifically pH5.5 of brown rice batter with time, temperature and yeast concentration as the independent variables. The results indicated that brown rice batter was well fermented to maintain pH5.5 at optimum conditions of 32°C for 6.26h using 1% yeast concentration. Fermentation at moderate acidity significantly increased the levels of protein, total ash, insoluble fiber, soluble fibre, minerals, phenolics, antioxidants, resistant starch, riboflavin, pyridoxine, nicotinic acid, γ-tocotrienol, and δ-tocotrienol. However, it reduced the contents of γ-oryzanol, γ-tocopherol, α-tocopherol, phytic acid, amylose and total starch. Foaming capacity, foaming stability, oil holding capacity, gelatinization temperatures, enthalpy and whiteness of BRF were increased after fermentation. In contrast, its swelling power, water solubility index, hot paste viscosity, breakdown, and setback significantly decreased. Microstructure of BRF was also influenced, where its starch granules released from its enclosed structure after fermentation. This investigation shows evidence that yeast fermentation modified the functionality of BRF and can be used as a functional food ingredient.