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(655b) 3D Time Variant Reactor Engineering Model for Red Wine Fermentations

Miller, K., UC Davis
Block, D. E., University of California, Davis

Abstract: 3D Time Variant Reactor Engineering Model for
Red Wine Fermentations

Red wine fermentations are
performed in the presence of grape skins and seeds to ensure extraction of
color and other phenolics. The presence of these
solids results in two distinct phases in the fermentor, as the solids float to the top to form a “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. To develop the heat
transfer component of the model, the heat
transfer properties of grapes were experimentally determined as a function of
fermentation progression. COMSOL was used to
solve all components of the model simultaneously white">utilizing a Finite Elements Analysis (FEA) approach (Figure 1).

Figure 1: Simulated velocity profiles inside a red
wine fermentor

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 (Figure 2).

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Figure 2: Epifluorescence microscopy of a grape seed
cross section, 500x

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