Effect of the addition of fatty acids on rice starch properties

The effect of the addition of the two fatty acids (stearic and linoleic acid) on starch pasting, thermal properties and the leaching of amylose during the gelatinization process are presented. The addition of stearic acid (C18:0) at 1.0% level (w/w, on the basis of starch) significantly changed starch pasting characteristics in peak viscosity (P < 0.05), breakdown (P < 0.001) and time to peak viscosity (P < 0.001) as measured by RVA. In contrast, the addition of linoleic acid (C18:2) showed less impact on the three RVA parameters. Thermal studies with DSC suggested that the addition of both fatty acids did not significantly influence the starch gelatinization behaviour as reflected in peak width and enthalpy but there was a decrease in peak temperature. However, the addition of the saturated fatty acid produced a significant decrease in the retrogradation endotherm (P < 0.01) compared to that of native starch. It is suggested that the saturated fatty acid complexes with amylose and is preferentially introduced into the starch granule. The double bond in the linoleic acid apparently hinders complexation. After complexation, hydrophobicity was further enhanced with the content of amylose in the hot-water soluble fraction being significantly reduced (P < 0.01) as determined by HPLC.