Effects of different content of EGCG or caffeic acid addition on the structure, cooking, antioxidant characteristics and in vitro starch digestibility of extruded buckwheat noodles

The effects of different types and content of polyphenol addition on the structure, cooking, antioxidant characteristics and in vitro starch digestibility of extruded buckwheat noodles were investigated in this study. The result showed epigallocatechin-3-gallate (EGCG) was more easily combined with starch to form complex than caffeic acid, and amylose tended to be combined with polyphenols to form more complex. Amylose had a protective effect on polyphenols during extrusion process, which led to a significant increase of polyphenol content and antioxidant activity of extruded noodles. The addition of polyphenol and high amylose corn starch (HACS) improved the cooking quality of extruded buckwheat noodles. The extruded buckwheat noodles with 20 % HACS and 1 % EGCG had the lowest cooking loss of 6.08 %. The addition of EGCG and HACS increased the content of resistant starch and reduced predicted glycemic index (pGI). The noodles with 20 % HACS and 3 % EGCG had the lowest pGI (63.38) and the highest resistant starch (RS) content (61.60 %). This study provides a theoretical basis for the development of low pGI extruded buckwheat noodles.