Low-temperature wine-making using yeast immobilized on pear pieces

A biocatalyst was prepared by the immobilization of Saccharomyces cerevisiae AXAZ-1 yeast cells on pear pieces and tested for grape must fermentation in both batch and continuous conditions. The immobilized yeast cells were stable and active even at low temperatures (<10 °C). Wine production under batch fermentation at 8 °C was completed within 15 days while at 3 °C it took 36 days. In continuous fermentation, the bioreactor was operated for 33 days, then stored for 12 days at 10 °C, and re-run for another 15 days without any diminution of the ethanol productivity. Total acidity of the produced wines remained within the ranges usually observed in dry wines, while volatile acidity was found in rather increased levels. The concentrations of higher alcohols (1-propanol, isobutyl alcohol and amyl alcohols) were relatively low, while ethyl acetate was detected at up to 118 mg l^-1, contributing to the fruity aroma of the wines produced. Preliminary sensory evaluations carried out in the laboratory indicated the fine quality of the produced wines.