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Aims: The aim of this study was to investigate the effectiveness of bread as substrate for γ-aminobutyric acid (GABA) biosynthesis, establishing a valorization strategy for surplus bread, repurposing it within the food chain., Methods and Results: Surplus bread was fermented by lactic acid bacteria (LAB) to produce GABA. Pediococcus pentosaceus F01, Levilactobacillus brevis MRS4, Lactiplantibacillus plantarum H64 and C48 were selected among 33 LAB strains for the ability to synthesize GABA. Four fermentation experiments were set up using surplus bread as such, added of amylolytic and proteolytic enzymes, modifying the pH or mixed with wheat bran. Enzyme-treated slurries led to the release of glucose (up to 20 mg g -1 ) and free amino acid, whereas the addition of wheat bran (30% of bread weight) yielded the highest GABA content (circa 800 mg kg -1 of dry weight) and was the most suitable substrate for LAB growth. The selected slurry was ultimately used as an ingredient in bread making causing an increase in free amino acids., Conclusions: Besides the high GABA concentration (148 mg kg -1 dough), the experimental bread developed in this study was characterized by good nutritional properties, highlighting the efficacy of tailored bioprocessing technologies as means to mitigate food wastage., Significance and Impact of Study: Our results represent a proof of concept of effective strategies to repurpose food industry side streams., (© 2021 The Authors. Journal of Applied Microbiology published by John Wiley & Sons Ltd on behalf of Society for Applied Microbiology.)

Food-grade waste and side streams should be strictly kept in food use in order to achieve sustainable food systems. At present, the baking industry creates food-grade waste as excess and deformed products that are mainly utilized for non-food uses, such as bioethanol production. The purpose of this study was therefore to explore the potential of waste wheat bread recycling for fresh wheat bread production. Waste bread recycling was assessed without further processing or after tailored fermentation with lactic acid bacteria producing either dextran or β-glucan exopolysaccharides. When non-treated waste bread slurry was added to new bread dough, bread quality (specific volume and softness) decreased with increasing content of waste bread addition. In situ EPS-production (dextran and microbial β-glucan) significantly increased waste bread slurry viscosity and yielded residual fructose or glucose that could effectively replace the sugar added for yeast leavening. Furthermore, fermentation acidified waste bread matrix, thus improving the hygienic safety of the process. Bread containing dextran synthesized in situ by Weissella confusa A16 showed good technological quality. The produced dextran compensated the adverse effect of recycled bread on new bread quality attributes by 12% increase in bread specific volume and 37% decrease in crumb hardness. In this study, a positive technological outcome of the bread containing microbial β-glucan was not detected. The waste bread fermented by W. confusa A16 containing dextran appears to enable safe bread recycling with low acidity and minimal quality loss., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Food‐grade enzymes (α‐amylase, amyloglucosidase, maltogenic amylase, and protease) were investigated for recycling waste bread back to wheat bread‐making process. Waste bread was efficiently hydrolyzed into sugars (up to 93% glucose yield) and the best combination of enzymes was α‐amylase (0.05 g/kg bread) and amyloglucosidase (2.5 g/kg bread). Selected enzyme hydrolysis processes were tested in wheat bread making as a (a) hydrolyzed slurry, that is hydrolyzed waste bread without solid/liquid separation and (b) syrup, that is liquid supernatant after centrifugation of the hydrolyzed waste bread. Both hydrolyzed bread slurry and syrup were successfully utilized to replace sucrose (2 and 4%) in bread making without affecting the bread quality when compared to the control bread. Techno‐economic assessment revealed that this approach is 12% more economical than the current mean to dispose the bakery waste. This recycling concept showed both technical and economic potential for bakery industries to overcome their excess bread production. Novelty impact statement: A new recycling process was developed by using enzymes to efficiently hydrolyze surplus bread into sugars. The use of those sugar‐rich slurries and syrups in bread rework did not affect the bread quality when compared to the control bread. The recycling concept was more economical than current means to dispose waste bread, revealing the technical and economic potential for bakery industries to overcome their excess bread production. [ABSTRACT FROM AUTHOR]

Occurrence of surplus bread (SB) is common in the baking industry. Edible surplus bread can be utilized as a new bread dough ingredient; however, it creates technological challenges that affect the quality of the new bread. In this study, the interactions of SB with dough macromolecules were studied in a gluten-starch model dough system and subsequent model bread. Moreover, dextran or maltosyl-isomalto-oligosaccharides (MIMO) were produced by dextransucrase preparation, incorporated into the dough containing SB, and their individual influence on dough rheology and bread structure was investigated. Compared to control model dough/bread, the addition of SB at 10% level significantly decreased extensibility of the dough, dough level, and specific volume (SV) of bread, despite standardized gluten content and optimized water absorption (WA). This confirms that SB constituents (especially gelatinized starch) deteriorate the dough structure-forming by interactions with gluten network. Dextran addition at appropriate level (0.7%) with optimized WA, shielded the gluten network from the interactions of SB, thus, increasing dough extensibility and softness. Furthermore, dextran-enrichment significantly reduced the hardness and staling of breads and increased the SV to the control model bread level. MIMOs, especially at low concentration, induced stronger interactions with gluten proteins than dextran. However, the addition of MIMOs reduced the SV of breads containing SB and did not reduce the overall crumb hardness despite partially preventing starch retrogradation in the early phase of storage. The protective interactions of dextran with dough macromolecules showed that in vitro dextran could be utilized to enable recycling of edible SB. [Display omitted] • Weissella confusa A16 dextran and MIMO were produced by enzyme preparation. • SB-gluten interactions increased dough tenacity, and reduced extensibility and SV. • Dextran softened the dough and efficiently protected gluten from interactions of SB. • Dextran improved the SV and retarded crumb firming with optimal level of 0.7%/FW. • MIMOs interacted with gluten, decreased SV but retarded starch retrogradation. [ABSTRACT FROM AUTHOR]

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. • Surplus wheat bread starch was enzymatically hydrolyzed to various degrees. • Hydrolyzed surplus bread was evaluated as a bread ingredient. • Starch hydrolysis improved dough development and texture of breads. • High-maltodextrin hydrolysate yielded highest bread volume and lowest staling rate. [ABSTRACT FROM AUTHOR]