Inhibiting effect of superheated steam processing on milling characteristics deterioration induced by storage of common buckwheat

Superheated steam (SS) was used to improve the milling characteristics of common buckwheat grains during storage. The changes in milling characteristics, pasting properties, micro-mechanical behavior and protein-starch interactions of buckwheat during storage were investigated. Results showed that the average particle size, color and pasting viscosities of untreated buckwheat decreased during storage, while the damaged starch content increased significantly. SS slowed down these deteriorations of milling characteristics by alleviating intracellular cleavage of starch during the process of buckwheat milling. SS also kept pasting properties of starch stable during the continuous heating and shearing process. X-ray diffraction showed less variation in crystallinity and stable structure of starch induced by SS. The results from SDS-PAGE and confocal laser scanning microscopy showed that these stabilizations were associated with the disulfide bonds of protein and its interaction with starch granules. It meant SS processing retarded the quality deterioration during storage and protected buckwheat starch against mechanical damage by promoting protein aggregation and letting the starch to be wrapped tightly by the protein, so as to protect the swollen starch granules from disintegration. Therefore, SS processing was potentially applicable for improving milling characteristics of buckwheat.