Management Strategies for Natural Cider Fermentation: Effects of sulfite addition and acidification in high- and low- tannin cultivars

Virginia is the largest apple producing state in the Southeast region of the United States and ranks 10th in most cideries in the US. Natural, or un-inoculated, fermentation methods are of interest to cider producers due to the potential for generating unique and complex aromas and flavors via fermentation with naturally present microbiota. The objective of this study was to determine the effect of common pre-fermentation sulfite addition and pH adjustment on cider chemistry and sensory outcomes for naturally fermented high- and low-tannin apple cultivars. Four treatment conditions were applied to both the high- and the low- tannin cultivars: acidification only, sulfites only, acidification and sulfites, and a control with no pre-fermentation juice chemistry adjustment. The eight experimental ciders were fermented using the Pied de Cuve (PDC) method for natural fermentation. Cider chemistry and sensory parameters were determined, and the treatments imparted key differences in both. Key findings were analyzed for pH, titratable acidity, volatile acidity, malic acid, free/total SO2, yeast assimilable nitrogen (YAN), total polyphenols, residual sugars, and ethanol. For the acidified condition, the pH was lowered to 3.2 using malic acid. Cider pH ranged from 3.36 ± 0.04 to 3.72 ± 0.07, reflecting a general trend toward rising pH over the course of fermentation. Juice tannins were 0.244 ± 0.003 g/L for Harrison and 0.12 ± 0.01 g/L for GoldRush. Tannins decreased during fermentation; however, Harrison ciders maintained a higher range compared to GoldRush. Sensory characteristics were determined using a Descriptive Analysis (DA) with a trained panel which produced 28 descriptors. Results were examined via analysis of variance (ANOVA) and significant differences for apple cultivar, acid adjustment, and sulfite use were found for both chemistry and sensory parameters. The interaction between high- and low- tannin content and sulfite use had the most impact on the cider chemistry and sensory attributes. This study helps to shed light on the extent to which pre-fermentation pH adjustment and/or sulfite additions can influence the outcomes of natural cider fermentation in both high- and low-tannin cultivars.