Insights into the effect of structural alternations on the digestibility of rice starch-fatty acid complexes prepared by high-pressure homogenization

The effects of chain length and addition level of saturated fatty acids on multi-scale structure of rice starch-fatty acid complexes prepared by high-pressure homogenization (HRFC) were investigated, as was the correlation between their structural changes and digestibility. Increasing the addition level of fatty acids increased complexing index (CI) of HRFC, but increasing the chain length decreased the CI. Compared with high-pressure homogenization treated starch, the HRFC presented a V-type polymorph with a higher degree of short-range ordered structure. Increased single helix contents, crystallinities, degree of ordered structures, and thermal stabilities with HRFC were confirmed as the chain length or addition level of the fatty acids increased. When the chain length increased to 18 C-atoms, the helical structure of the resulting HRFC changed from V7 to V6, and the complex type changed from IIb to IIa. Combined with the digestion profiles of HRFC, the degree of short-range ordered structure, single helix contents, crystallinity, mass fractal dimension, and thermal stability were negatively correlated with rapidly digestible starch contents but positively correlated with the slowly digestible starch and resistant starch contents. Overall, these results suggested a systematic correlation mechanism of the multi-scale structure in regulating the digestion properties of starch-fatty acid complexes.