Altered leaching composition of maize starch granules by irradiative depolymerization: The key role of degraded molecular structure.

The molecular composition of starch leachates from starch-based foods has been recently recognised as a crucial determinant of food properties. However, there is limited knowledge on the regulation of this composition through irradiative depolymerization of starch. This research investigates the leaching behaviour of maize starch depolymerized by electron beam irradiation, and the relationship between the composition of leached starch and structures of modified starch granules. The analysis using 1H NMR spectroscopy confirmed a decrease in the degree of branching (from 4.4 % to 2.8 %), while size-exclusion chromatography identified a newly-derived amylopectin fraction of a smaller hydrodynamic radius (approximately 60-80 nm). The structural properties of the starch granules were also analysed, revealing an increased BET-area of granules and reduced total crystallinity after depolymerization. In the leachates of swollen granules, the bimodal distribution of starch molecules evolves into unimodal with the increase of the irradiative dosage, while modified starch leached more starch molecules with Rh < 10 nm. The results of principal component analysis and Pearson correlation analysis indicate that the degree of branching of degraded starch molecules, as well as the newly-derived amylopectin fraction, significantly correlates (p < 0.01) with the molecular size of leached starch molecules (Rh < 10 nm). It is thus proposed that the cleavage of α-1,6 linkage may be a critical factor in controlling the leaching process of irradiated starch granules. This study highlights the potential of irradiative degradation to control the molecular composition and structure of starch leachates, thereby optimizing the properties of starch-based foods.