In vitro digestibility and structural control of rice starch-unsaturated fatty acid complexes by high-pressure homogenization

Abstract

This study emphasized on structural alteration of rice starch-unsaturated fatty acid complexes by adding trans-2-dodecaenoic acid (t12), trans-oleic acid (t18), cis-oleic acid (c18) and linoleic acid (loa) with different concentration under high-pressure homogenization treatment, and further illustrated the underlying mechanism of modulating digestibility. Results showed that the complex primarily presented as V6 or type IIa polymorph; complex index, content of ordered structure and thermal stability appeared to be positively correlated to the concentration of unsaturated fatty acids. t12 was too mobile to form single helix, leading to the formation of loose matrix; t18 fitted better within the cavity of starch than c18, and formed structural domain with higher compactness and thermal stability; Rloa had lower complex index but higher degree of short-range order, and tended to form alternating amorphous and crystalline structure. The digestibility was higher in the order of Rloa, Rt18, Rc18 and Rt12.

Keywords: Degree of unsaturation; High-pressure homogenization; In vitro digestibility; Multi-scale structure; Rice starch-unsaturated fatty acid complex.