Carbohydrate transformation and gluten immunoreactivity in bread-based amazake: carbohydrate and protein profiling with electronic eye colour analysis

This study examined the valorisation of stale bread in amazake production. Carbohydrate transformation, gluten degradation and colour development were assessed in products prepared with rice or wheat bread koji. Bread supplementation increased mono- and oligosaccharide concentrations, with wheat bread yielding the highest levels of trehalose, kojibiose, nigerose and isomaltose. Amazake produced with wheat bread koji showed higher levels of free amino acids. Principal component analysis revealed distinct sugar composition patterns. Among bread containing variants, wheat bread koji with rice addition resulted in the lowest gluten levels, remaining close to, but slightly above the low-gluten threshold. Colour analysis differentiated the samples according to bread type and process conditions. Overall, both koji type and saccharification substrate influenced amazake properties across all analysed parameters. Stale bread proved to be a suitable substrate for koji-mediated processing, enabling the production of amazake with enhanced carbohydrate complexity and reduced gluten levels.