Effect of storage of immobilized cells at ambient temperature on volatile by-products during wine-making

Duration, effective storage and reuse of immobilized yeast cells on kissiris, γ-alumina pellets and apple pieces at 30 °C were investigated and the effect of initial sugar concentration, immobilization support and maximum storage time period on volatile by-products profile was studied. The immobilized biocatalysts were allowed in the fermented must after the end of fermentation for extended storage time periods at 30 °C, before reactivation and reuse in wine fermentations. Immobilized cells were stored and remained active for longer time periods (up to 80 days) than free cells. The results showed that there were no negative effects on volatile product composition during storage. Duncan’s multiple range test showed that in some cases storage resulted in statistically increased levels of acetaldehyde in the produced wines, while ethyl acetate concentration ranged in normal levels. Higher (1-propanol and isobutanol), amyl alcohols and methanol content remained in low levels in all cases, indicating an improved quality product.