Different Milling Methods: Physicochemical, Pasting and Textural Properties of Rice Flours

Abstract

Background and Objective: Milling methods had a marked effect on the properties of flour. This study was conducted to investigate the chemical composition and physicochemical properties of rice flour to utilize the suitable rice for product development with desired characteristics. Materials and Methods: The effect of three milling methods (wet milling, semi-dry milling and dry milling) was investigated on the physicochemical, pasting and textural properties of rice flour using five varieties with varied amylose content. Results: Dry-milled flour had the highest protein, fat, damaged starch, particle size, water absorption index and water solubility index, compared to wet-milled and semi-dry-milled flours. Moreover, these determined parameters of wet-milled flour were rather similar to semi-dry-milled flour. Partial gelatinization occurred during the dry-milled method. The ΔH_gel and temperature of gelatinization of wet-milled flour were similar to those of semi-dry-milled samples. There was no effect of milling method on the retrogradation. The physicochemical and textural properties of flour also depended on the amylose content and although this had no clear effect on gelatinization, retrogradation tended to increase with increased amylose content. Stickiness and adhesiveness tended to decrease as the amylose content increased. Conclusion: Suitable rice milling depends on the desired food characteristics. Rice cookies should be made from dry milling rice flour because of the high amounts of damaged starch and large particles, resulting in fracturability and porosity in texture. Wet-milled-rice flour is useful for making desserts and foods which require stickiness, smooth texture and oily mouthfeel. Semi-dried rice flour may be attractive ingredients for non-gluten free products.