Insights into maize starch degradation by high pressure homogenization treatment from molecular structure aspect

High-pressure homogenization (HPH) is a common physical method used for starch modification. In this study, starch molecular structure in terms of chain-length distribution (CLD) and molecular size is characterized to explore the structural variations during HPH and its internal relations. It is found that: 1) the molecular size is significantly reduced by HPH treatments and further gradually decreases with HPH pressure increasing; 2) HPH degrades the long amylose chains with degree of polymerization (DP) ~ 2000-20,000 into short- and intermediate-amylose chains with DP ~ 100-1000 and DP ~ 1000-2000; 3) by HPH treatment, the proportion of amylopectin chains with DP ~ 6-12 and DP ~ 12-24 decreases while that with DP ~ 24-36 and DP ~ 36-100 increases, whereas, the amylopectin CLDs between HPH treated starch samples are not significantly varied; and 4) by a subtraction analysis, the molecular size of HPH treated starches shows a strong correlation with the proportion of degraded long amylose chains, indicating these long amylose chains might play a critical role in maintaining the large molecular size of starch. This study provides a further understanding of molecular features from the individual chains assembling into a whole branched molecule.