Comparative assessment of ethanol production from six typical German waste baked products

Abstract

This study investigates the potential for bioethanol production of six types of typical German leftover baked products: bread rolls, pretzel rolls, fine rye bread, white bread, pastry, and cream cakes. The experimental setup consisted of two experiments—one as a control and another with the addition of diammonium phosphate (DAP) to the mash. In terms of monosaccharide concentration at 30% dry matter (DM), white bread mash exhibited the highest level at 251.5 g/L, while cream cakes mash had the lowest at 186 g/L. The highest ethanol production occurred after 96 h of fermentation with rye bread, yielding 78.4 g/L. In contrast, despite having the highest monosaccharide levels, white bread produced only 21.5 g/L of ethanol after 96 h. The addition of DAP accelerated monosaccharide consumption in all baked products, with cream cakes completing the process in just 24 h. Bread rolls, pretzel rolls, pastry, and white bread fermentations finished within 72 h. Ethanol yields significantly increased in three DAP samples, with pretzel rolls yielding the highest ethanol concentration at 98.5 g/L, followed by white bread with 90.6 g/L, and bread rolls with 87.7 g/L. DAP had a substantial impact on all samples, reducing fermentation time and/or increasing ethanol yield. This effect was particularly pronounced with white bread, where it improved conversion efficiency from 17 to 72%, resulting in 90.6 g/L of ethanol. These results demonstrate that waste baked products hold substantial potential for bioethanol production, and this potential can be further enhanced through the addition of DAP.