Malolactic fermentation (MLF) is commonly carried out in winemaking as a tool for deacidification, altering the sensory profile and increasing the microbial stability of a wine. MLF must be monitored and sometimes stopped so as to prevent unwanted microbial spoilage. Current methods for monitoring MLF are both expensive and labor intensive and a low cost automated sensor could be of practical relevance for the wine industry. Due to the different densities of malic acid and lactic acid, density measurements could be used to monitor MLF. This multifaceted project involved two key studies, a study of density during MLF in a Zinfandel wine and a study of the pressure tube density meter during MLF. The goal of the study of density during MLF in a Zinfandel wine was to determine if a correlation between malic acid concentration and density exists and to write a predictive curve which can be used to determine malic acid concentration from density measurements. The goal of the study of the pressure tube density meter during MLF was to assess the sensitivity, compatibility and potential for adapting the pressure tube technology used in Cypress Semiconductor’s Integrated Fermentation Control System (IFCS) to monitor malic acid concentration during MLF with a density derived predictive curve. Daily samples were taken from three replicate 208 Liter fermenters and analyzed for density and L-malic acid concentration in a laboratory setting for the duration of MLF of a Zinfandel wine. The regression models fit to the data did not show evidence of a correlation between malic acid concentration and density with the coefficient of determination for each fermenter being R2Tank1 = 0.01092, R2Tank2 = 0.00085, R2Tank3= 0.01826 and R2Tank_all = 2.082-5. The high standard deviations in density for each data set (SDTank1 = 0.0051, SDTank2 = 0.0038, SDTank3 = 0.0046 and SDTank_all = 0.0045) implied a lack of sensitivity in testing methodology due to a volumetric variation not accounted for in density calculations. The data collection software disconnected from the IFCS units during alcoholic fermentation, halting data collection. Without data collection, it was impossible to assess the capabilities of the IFCS as a MLF sensor.
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