Mémoire
| Résumé : | In a context of growing concern over global food waste, and bread waste in particular, new initiatives are emerging to address this issue in an intelligent way. One such initiative comes from the brewing sector, which is increasingly interested in reducing its emissions and carbon footprint. Some breweries are eager to integrate into a circular economy by recovering unsold bread and reusing it in the brewing process, substituting part of the barley malt with this bread. Such a substitution is not without concerns or challenges: the impacts on the physicochemical characteristics of beer must remain minimal to ensure continued viable production. Some breweries are already experimenting with it, and scattered scientific studies address the topic. This thesis follows in the footsteps of this research, investigating the impact of substituting part of the malt with different types of bread, at varying concentrations (up to 40%), and under different brewing profiles. The study focuses on the characteristics of the wort and then compares a beer brewed with 40% bread to a 100% malt control beer. The pH of both wort and beer is only slightly affected by the addition of bread, showing a small decrease. Colour (EBC) consistently decreases when bread is added, both for wort and beer. Concentrations of polyphenols and free amino nitrogen both decline with increasing bread content, but not to levels that would disrupt proper beer production. Dry extract and dry matter extraction yield increase slightly, whereas fermentable sugar content shows a small drop, resulting in beers with similar alcohol volumes, but slightly lower for the bread beer. Bread addition increases cold wort viscosity but reduces it when hot, due to differences in β-glucan and arabinoxylan composition between bread and malt, with the viscosity of these molecules being differently affected by heat. Filtration kinetics are therefore altered by the addition of bread, in opposite ways for hot versus cold filtration. Sensory evaluation of the bread beer reveals no major differences compared to the 100% malt beer. We conclude that brewing a beer by replacing part of the malt with bread is a sufficiently feasible and promising approach for the development of this emerging sector. |
