Modeling the effects of initial nitrogen content and temperature on fermentation kinetics of hard cider Original Research Article

Hard apple cider manufactured as a value-added product will increase consumption of excess American apples and give impetus to local industry. For larger scale productions, a mechanistic model that could predict the fermentation kinetics would be a useful tool for understanding and designing processes. Hence, the objective of this study was to apply a simple mechanistic model to predict fermentation kinetics of hard cider from Michigan apples and study the combined effect of initial nitrogen and temperature on fermentation. Kinetic parameters of the primary mechanistic model based on Monod kinetics were estimated non-linearly via the Runge–Kutta method. Four coupled ordinary differential equations were used for each of the four dependent variables, yeast cell concentration, nitrogen, sugar and ethanol concentration. For the secondary model, it was proposed to model the effect of temperature and initial nitrogen content on the kinetic parameters of the primary model with an Arrhenius relationship. The current study is the first known application of a mathematical model to the hard cider fermentation process.