Juice Clarification with Pectinase Reduces Yeast Assimilable Nitrogen in Apple Juice without Affecting the Polyphenol Composition in Cider

Abstract

The term "cider" refers to the fermented beverage produced from apples. The rapid growth in the cider industry coupled with the prominence of traditional, or craft, approaches emphasizes the need for research on cider production. A common problem in ciders is the production of sulfur off-aromas by yeast during fermentation. Prefermentation juice clarification has the potential to reduce the occurrence of unwanted sulfur off-aromas. Concerns that prefermentation juice clarification will reduce the yeast assimilable nitrogen (YAN) and polyphenols in the juice have limited the application of this practice by cider makers. In this study, 3 clarification methods were applied to 'York' apple juice, that is, static settling, centrifugation, and pectinase. Raw (control) and clarified juice were fermented to cider, and the impact of clarification on the physicochemical parameters, amino acids and polyphenol content of the juice and cider was assessed. Juice clarification by pectinase decreased YAN by 50%, while static settling and centrifugation increased the concentration of most amino acids by 83%. All clarification treatments lowered the concentration of total polyphenols in the juice (from 60% to 30%, P < 0.05) and affected the individual polyphenols in the juice but these changes were not evident in the ciders. These findings demonstrate that prefermentation juice clarification results in changes in the chemistry profiles of apple juice. These changes were however not evident in the ciders. This approach therefore has the potential to limit the production of sulfur off-aromas during cider production without adverse effects on quality. PRACTICAL APPLICATION: Clarification of apple juice changes polyphenol and nitrogen contents, factors known to affect cider quality. However, these differences in the chemical profile of apple juice may not be reflected in the finished ciders. These findings demonstrate that juice clarification can be employed in cider making without affecting the quality. Cider makers should not assume that changes in apple juice imparted by clarification will be reflected in the finished ciders. Outcomes should be measured in finished ciders, rather than juice to accurately evaluate effects of the processing steps on quality.

Keywords: Malus xdomestica; fermentation; free amino acids; static settling; ‘York’ apples.