3D Time Variant Reactor Engineering Model for Red Wine Fermentations

Authors: 
Miller, K., UC Davis
Block, D. E., University of California, Davis
Red wine fermentations are performed in the presence of grape solids (skins and seeds) to ensure extraction phenolics. This results in a heterogeneous fermentation system, as the solids float to the top to form a porous solid-liquid “cap.” Modeling of red wine fermentations is, therefore, complex and must consider spatial heterogeneity to predict fermentation kinetics. We have developed a reactor engineering model for red wine fermentations that includes the fundamentals of fermentation kinetics, heat transfer, diffusion, and compressible fluid flow. COMSOL was used to solve all components of the model simultaneously utilizing a Finite Elements Analysis (FEA) approach.

A kinetic model for the extraction of phenolics from grapes as a function of temperature and ethanol concentration was derived, incorporating the release of phenolics from grape cells, the adsorption equilibria of phenolics onto cell wall material, and the reaction of phenolics in solution. The findings of this model were supported by bright field and epifluorescence microscopy.

This extraction model was then combined with the fermentation reactor engineering model, enabling prediction of phenolic extraction as a function of fermentation progression and winemaking conditions.