Influence of Water Activity on Physico-Chemical Properties of Proteins from Selected Oilseed Flours

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The objective of investigation was to study the influence of water activity on physicochemical properties (PCP) of defatted groundnut (Arachis hypogea), sunflower (Helianthus annus), rice bran (Oryza sativa) and soybean (Glycine max). Moisture free samples equilibrated at relative humidity (RH) levels from 22 − 84% were used for determination of PCP. Bulk density of samples decreased with increasing RH levels for sunflower, rice bran and soybean. Water absorption and emulsion activity of groundnut and sunflower increased with RH levels. However, an opposite trend was seen for rice bran and soybean. Fat absorption of all samples increased with increasing RH. Protein solubility of groundnut and sunflower was very high at RH of 84% in alkaline pH range. Protein solubility of rice bran was not affected by RH, whereas for soy flour it decreased with increasing RH. It can be concluded that water activity influenced the PCP of oilseed flour to a significant extent.