Effect of High-pressure Homogenization on Molecular Structure and in Vitro Digestibility of Rice Starch
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Abstract:
To clarify the effects of different high-pressure homogenization (HPH) conditions on the molecular structure and digestibility of rice starch, the changes in the molecular structure of the rice starch before and after HPH were evaluated by gel permeation chromatography-multi-angle laser light scattering, nuclear magnetic resonance spectroscopy and iodine colorimetry in this study. Comparison was made on the digestibility of native and HPH-treated rice starch following in vitro simulation. The results showed that with the increase of homogenization pressure and cycles, both the average molecular weight and mean square rotation radius decreased, with the main molecular weight distribution shifting from the high-molecular weight region (5×106~1×107 g/mol and >1×107 g/mol) towards the low-molecular weight region (1×106~5×106 g/mol and<5×105 g/mol). These results indicated the breakdown and degradation of starch molecular chains. The decrease in the proportion of the α-1,6 linkages suggested the damage of the branched structure of starch, causing the increase of amylose content. In addition, an ordered domain was formed due to the re-aggregation between amylose and the starch molecules with appropriate molecular weights during HPH, which facilitated the increase of resistance to digestion for the rice starch. The results of this study will provide a foundation and fundamental data for regulating the digestibility and nutritional functions of starch and starchy foods through HPH.
