Amylose-lipid complex formation during cooking of rice flour

Abstract

The effects of cooking rice flour in the presence of myristic, palmitic and stearic acid on amylose-lipid complex formation, water solubility and pasting properties were studied. Different fatty acids were added to rice flour, at 1.5, 3.0 and 4.5% levels, and cooked in Visco-amylograph at 95°C for 30, 60 and 90 min. Amylose-lipid complex formation increased and water-solubility decreased with the increase in levels of all the fatty acids in rice paste cooked for 30–90 min. Complexing of amylose with all the fatty acids increased with the increase in cooking time. Myristic acid had the highest ability to form the complex and stearic acid the lowest. Iodine spectra of rice paste cooked with and without lipids were also determined to confirm the formation of amylose-lipid complexes. Both λmax and ratios of absorbances at 630 and 520 nm decreased with the increase in levels of all the fatty acids. Myristic acid caused a greater reduction in λmax and ratios of absorbance. Addition of all the fatty acids increased the pasting temperature, peak viscosity, viscosity at 95°C and viscosity at 50°C of rice paste. Consistency coefficient and flow behaviour indices of rice pastes cooked in the presence of different fatty acids were also determined using a Brookfield viscometer. Consistency coefficient increased with the increase in levels of all the fatty acids and the increase was more pronounced with myristic acid.