Effects of pullulanase debranching and octenylsuccinic anhydride modification on the structural properties of maize starch-green tea extract complexes

Green tea (Camellia sinensis) is a traditional beverage and its ethanolic extract (GTE) is rich in catechins, having numerous biological activities. However, commercial formulations of catechin-rich GTE are limited by low aqueous solubility, and high oxidation sensitivity. Here, normal maize starch was modified by pullulanase debranching or octenylsuccinic anhydride (OSA), and its inclusion complexes with catechin-rich GTE were prepared. Effects of debranching and OSA-modification on the degree of complex formation and characteristics of inclusion complexes were examined using complementary techniques. Results demonstrated that bioactive compounds of GTE efficiently cooperate with debranched or OSA-modified starches to form inclusion complexes. Moreover, inclusion complexes were subjected to a one step extraction followed by UHPLC-LTQ-Orbitrap-MS/MS analyses, which demonstrated selective inclusion complexation for distinct metabolites of GTE, with modified starches based on host-guest interaction. By debranching, maize starch formed a complex with GTE, demonstrating the highest recovery yield of 67.81% in comparison to other starches. Storage studies showed that the retention of distinct metabolites of GTE in complexes could achieve 92% after 28 days, and the antioxidant activity of the GTE-DB540 and GTE-DB520 was higher than that of others at any time and achieved around 90% after 28 days storage. This study reveals that the interactions between debranched maize starch and catechin-rich GTE are effective, and complexes can improve bioactive ingredients' stability.