In-depth exploration on the effects of organic nitrogen addition during different fermentation periods on the quality of cider

Nitrogen is an essential element for the growth and metabolism of Saccharomyces cerevisiae, and has a great impact on the quality of cider. In this study, the effects of organic nitrogen addition at different stages of fermentation process on the quality of cider were systematically explored. The main projects included the analysis of fermentation rate, yeast growth, organic acids, amino acids, and volatile aroma compounds. The results indicated that organic nitrogen addition speeded up fermentation rate and shortened fermentation time. The organic nitrogen addition before fermentation and at the early stationary phase altered the composition of organic acids in cider. Moreover, with the addition of organic nitrogen at three stages of fermentation (pre-fermentation, logarithmic and stable phases of yeast growth), the total concentrations of volatile aroma substances in ciders were 10.57 mg/L, 11.97 mg/L and 11.05 mg/L respectively, which were all significantly higher than that in control group (9.69 mg/L). A close relationship between free amino acids consumed during fermentation and volatile aroma compounds produced was revealed by partial least-squares regression analysis. Overall, this study provided a new strategy for cider quality improvement by evaluating the effects of organic nitrogen on the aroma composition of cider.