Interactions in starch co-gelatinized with phenolic compound systems: Effect of complexity of phenolic compounds and amylose content of starch.

Maize starches of different amylose contents were co-gelatinized with caffeic acid (CA), quercetin (Qu) and epigallocatechin gallate (EGCG), respectively. The decomposition temperature of waxy maize starch (WS)-CA blends was increased compared to WS, while that of normal maize starch (MS) and high amylose starch (HS) was decreased. The more complex of the phenolic compounds, the lower the decomposition temperature of the MS. The results of Fourier-transform infrared spectroscopy suggested that CA increased short range ordered structure of gelatinized WS but decreased that of gelatinized MS and HS. Hydrogen bonds associated with CA and starch led to the arrangement of ordered structures in different starch. Nuclear magnetic resonance (NMR) indicated that all hydroxyl groups of CA and EGCG formed hydrogen bonds, while hydroxyl group at C-4' of quercetin had priority to form hydrogen bonds. During co-gelatinization process, more single helixes were induced in MS by CA than Qu or EGCG did.