The North Carolina Journal of Mathematics and Statistics

Statistical Analysis of Yeast Nutrient in Hard Cider Brewing

Jamie Leigh Rowell, John Wagaman


  In brewing, it is widely known that trace elements, particularly zinc, are required by yeast in order to grow and ferment. The most sensitive and time-consuming step of cider production is the fermentation process, and problems encountered during this process can lead to prolonged fermentation time and the deterioration of cider quality. Several studies have been published on the optimal zinc concentration to increase the rate of fermentation, but few have studied this process in quantities that are practical to the average homebrewer. Furthermore, homebrewers more commonly supplement with yeast nutrient rather than zinc, as yeast nutrient is more widely available and easier to use. Given that the use of zinc in increasing fermentation rate has been so widely studied, it may be useful for homebrewers to know if zinc is as useful in increasing fermentation rate on a smaller scale. In this study, we explore different methods of increasing fermentation rate by supplementing with various levels of zinc and yeast nutrient, as well as a combination of zinc and yeast nutrient. We present statistical models that describe specific gravity as a function of time, identify underlying causes of variability in specific gravity, and determine if supplementing with zinc is an effective method of increasing fermentation rate on a smaller scale. The results of this study show that supplementing with the full recommended amount of yeast nutrient is the most effective method of increasing fermentation rate, while the other treatment levels were not significantly different from the control treatment.

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