Insight into the spatial distribution and interaction model of heat-induced micro- and nano-starch/myofibrillar protein blends.

This work investigated the gelatinizing and hydration properties of raw and milled tapioca starches at micron and nano scale as well as their effects on gelation of myofibrillar proteins (MP) from Ctenopharyngodon idellus by analyzing rheology, texture and microstructure of heat-induced MP/starch blends. Milling induced starch granules damage to micron and nano scale, causing a fall in starch swelling power and a jump in water solubility. Among raw and milled starches, nano-starch had the best reinforcement effect on MP gel, i.e., MP/nano-starch showed the lowest critical gel concentration, highest G', strongest resistance to deformation and highest texture performance. Correlation analysis revealed that starch water solubility was responsible for the reinforced MP gel rather than starch swelling power. A schematic model was proposed for illustrating the interaction of starches and MP. All the blends had the ordered filamentous network as the basic skeleton, with some starches (granules and their fragments) in the voids or on the edge or surface of MP filaments as inert fillers, and some (chain segments) embedded in the filaments as active fillers. Almost all nano-starch were actively filled into the MP filaments to enhance the strength of filaments, thus achieving the best reinforcement effect on MP gel.

Effects of wet-media milling on multi-scale structures and in vitro digestion of tapioca starch and the structure-digestion relationship.

This work aims to understand the relation between multi-scale structural changes and in vitro digestion of tapioca starch modified by wet-media milling. The native starch granules were smooth and difficult to digest due to the hindrance of enzymes entry into the granules by the concentric shell architecture. However, 1-min milling could break the smooth surface of starch granules, weakening shell architecture and increasing k1 (digestion rate). Moreover, 5-15-min milling could greatly disrupt the short-range ordered structure and transform it into the amorphous phase to enhance k1. The increase of milling time to 30-420 min mainly interrupted the glycosidic bonds of the amorphous phase, allowing the production of amylose and amylopectin fragments, achieving continuous increase of k1. Despite the increasingly severe damage caused by milling to multi-scale structures, the disruption of shell barrier on the starch surface was the most critical for digestion, followed by short-range ordered structure breakage.