Preparation of low estimated glycemic index (eGI) chestnut flours using enzymatic debranching and heat moisture treatment

Abstract

A low estimated glycemic index (eGI) chestnut flour was prepared using a combination of pullulanase debranching and heat moisture treatment (HMT). The modified samples had a lower eGI range of 49.1–53.0 compared to native chestnut flour (NCF) which had an eGI of 67.3. Furthermore, the dual treatment was found to be more effective than a single treatment. The total starch content decreased from 57.0 to 47.1 g/100 g after debranching and HMT, resulting in an increase in amylose content from 30.6 % to 48.5 %. A 1H NMR (nuclear magnetic resonance) analysis revealed that modified flours showed a reduction in α-1,6-glycosidic bonds. NCF exhibited a C-type crystal structure, while the debranched samples showed B+V-type crystallinity with an increased peak at 20°(2θ). Debranching increased the proportion of short linear chains, which facilitated the formation of amylose-lipid complexes. HMT resulted in partial starch gelatinization and the breakage of amylopectin. These findings emphasize the potential applications of debranching and HMT in producing chestnut flour with a low eGI, which can further be used in functional food products.