Validation of a Phenomenological Model for the State Variables in the Non-Isothermal Wine Fermentation

ABALLAY PABLO; GUSTAVO SCAGLIA; MARTHA D. VALLEJO; ORTIZ, OSCAR ALBERTO; SERRANO, MARIIO EMANUEL; CARMEN A. MENGUAL; ROMOLI SANTIAGO

Rosario

Congreso; VII Congreso Argentino de Ingeniería Química - CAIQ2013; 2013

Asociacion Argentina de Ingenieros Quimicos

In winemaking, fermentation kinetics is temperature-dependent. Also, quality, quantity and rate of aroma compounds may be ?fine-tuned? by manipulating the temperature. Hence, oenologists use variable temperature profiles during the fermentation, to obtain high-quality varietal wines. This non-isothermal batch operation must be carefully controlled to avoid sluggish or stuck fermentations and favor the appearance of the preferred sensory features: acidity, ethanol level, and sugar depletion. Isothermal mathematical models cannot be used for controlling these bioprocesses. So, more rigorous and accurate models are necessary. This work proposes an improved non-isothermal phenomenological model for the alcoholic fermentation step in winemaking that considers temperature as the most critical variable influencing the mentioned bioprocess. The developed model, based on previous ones published by authors, couples mass and energy balances between the reactor and its cooling jacket. It predicts viable cells, total fermentable sugars and ethanol concentrations, carbon dioxide released on bioreactor temperature. It is considered a new expression depending on temperature for: maximum specific cellular growth and death rates, and the carbon dioxide released at 85-95% of its maximum value. The model has been validated, with an adequate accuracy, by own lab-scale fermentations and by data from literature for the four state variables of the process. Simulations at different constant temperatures and for predefined temperature trajectories, between 10 - 40ºC, were performed. Given that attained results are suitable, this model can be used to track complex temperature profiles to obtain high-quality wines, and in control and optimization strategies as well.