Multi-scale structure provides new insights into the physicochemical and digestive behaviors of kiwifruit (Actinidia spp.) starch obtained from defective hard fruits.

The anti-digestive mechanism of kiwifruit starch obtained from defective hard fruits was explored from multi-scale structural perspective. The results indicated that kiwifruit starch belonged to small-granule B-type starch, characterized by stable semi-crystalline structure with hilum at the geometric center and relatively indistinct growth rings. Compared with commercial wheat and potato starch, it contained higher proportion of long-chain amylopectin, had higher protein and resistant starch content (63.76-64.14 %), and lower α-amylase activity, which contributed to its excellent anti-digestive behaviors. Kiwifruit starch had superior thermal stability and thickening capacity but weak gel strength. There were significant relationships between structure of kiwifruit starch and its digestion and pasting properties. Specifically, digestion properties were positively related to amylose content but inversely related to relative crystallinity, which allowed for easier aging and higher cold-paste viscosity. This study reveals the potential structure-function linkage of kiwifruit starch and lays foundation for its innovative applications in food fields.