Removal of internal lipids enhances the effect of proanthocyanidins on maize starch retrogradation.

Internal lipids of normal amylose (NMS) and two high amylose (HMS56, HMS72) maize starches were removed to investigate the effect of proanthocyanidins (PA) on starch short-term (1 d) and long-term (21 d) retrogradation. Removal of internal lipids decreased the degree of retrogradation in PA-starch complexes after 1 d and 21 d retrogradation. The relative crystallinity (RC) of PA-NMS, PA-HMS56 and PA-HMS72 without internal lipid complexes after short-term retrogradation decreased by 5.46 %, 6.47 % and 7.52 % when the addition of PA was 10 %, respectively, compared with corresponding samples without PA. Compared with PA-native starch complexes, PA-starch without internal lipids complexes had lower correlation length (ξ) and tended to form smaller polymeric assemblies suggesting that the size of aggregates growing within gels was decreased because more PA molecules impeded the reformation of ordered starch structures. Removal of internal lipids exposed hydrogen bonds and the cavities of amylose, promoting the interaction between PA and amylose and more formation of PA-amylose complexes, which in turn reduced amylose available for crystal nucleus formation delaying retrogradation. Overall, retrogradation could further slow down by PA after internal lipid removal, which provided a new perspective for enhancing the modification effect of PA on starch.