Physicochemical properties of rice flour as affected by alkaline soaking and washing treatments

Pedcharat, Kasarin; Jangchud, Kamolwan; Prinyawiwatkul, Witoon

Physicochemical properties of rice flour as affected by alkaline soaking and washing treatments

2021

Pedcharat, Kasarin | Jangchud, Kamolwan | Prinyawiwatkul, Witoon

Effects of alkaline [NaOH, saturated Ca(OH)₂ and/or limewater] soaking and subsequent washing (with water vs. without washing) treatments on physicochemical properties of rice flour were investigated. Alkaline soaking treatment generally caused a loss of granule angularity but some birefringence was observed for unwashed alkali‐soaked flour granules. After soaking, protein content of the flours significantly (P < 0.05) decreased but swelling power significantly (P < 0.05) increased compared to the control (soaked in water). The washed flours had lower protein content than unwashed flours (3.77–6.87% vs. 5.26–7.87%). The NaOH‐soaking treatment yielded higher swelling power and solubility, respectively, for unwashed and washed flours. Alkaline soaking increased breakdown but decreased pasting temperature, trough viscosity, final viscosity and setback of the paste compared to the control. Compared to the control, hardness of soaked flour paste was lower due to lower final viscosity and setback. Overall, physicochemical properties of rice flour could be modified by alkali‐soaking and washing treatments.

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