The molecular state of gelatinized starch in surplus bread affects bread recycling potential

Abstract

Surplus bread is a major bakery side stream that should be strictly kept within the human food chain to reduce waste and ensure resource efficiency in baking processes. Optimally, surplus bread should be recycled as a dough ingredient, however, this is known to be detrimental to the volume and texture of bread. The purpose of this study was to investigate how gelatinized starch in surplus bread, untreated or enzymatically hydrolyzed, affects dough development, bread volume and textural attributes. Starch was hydrolyzed to various degrees using commercial α-amylase and amyloglucosidase. Bread hydrolysates containing different carbohydrate profiles (untreated, 75%, 57%, and 26% starch remaining) were evaluated as dough ingredients. More complete starch hydrolysis resulted in better dough visco-elastic properties and higher dough level, and reduced dough water absorption by 13%. Nonetheless, breads containing hydrolysate with high-malto-oligosaccharides had the lowest intrinsic hardness and similar volume yield when compared to control bread. Furthermore, compared to untreated slurry, the hydrolysate with high-malto-oligosaccharides, reduced crumb hardness by 28% and staling rate by 42%, and increased specific volume by 8%. The present findings show that enzymatic hydrolysis dramatically transforms the impact of gelatinized starch. Thus, by selecting correct bioprocessing approaches, bread recycling performance may be significantly improved.