Impact of Nitrogen Supplementation and Reduced Particle Size on Alcoholic Fermentation and Aroma in Nitrogen-Poor Apple and Pear Mashes

The aim of this study was to enhance the nitrogen supply through three different mash treatments and to investigate their effects on fermentation dynamics, yeast biomass accumulation, and the concentration of aroma-active volatiles in nitrogen-poor apple and pear mashes. In terms of nitrogen supplementation, the addition of diammonium phosphate (DAP) and amino acids (AS) accelerated fermentation and reduced the fermentation duration by 4–6 days in three out of four investigated fruit varieties. One pear variety showed sluggish fermentation, which was slightly improved by reducing the particle size (<3 mm) and significantly improved by nitrogen addition. Notably, AS supplementation resulted in a significant reduction in residual sugar concentrations and led to the highest yeast biomass accumulation across all four fruit mashes. Nitrogen supplementation significantly altered the composition of aroma-active volatiles, notably by increasing higher alcohols such as propyl alcohol, 2-methylpropanol, isoamyl alcohol, and 2-methylbutanol. The addition of AS was more effective in increasing higher alcohols, such as isoamyl alcohol and phenethyl alcohol, while decreasing the off-flavor acetaldehyde.