Estudos cinéticos da fermentação alcoólica da produção de vinho e da fermentação acética da produção de vinagre de vinho de caju.

Abstract

At present the cashew culture has been expanding and the Brazilian production of tropical fruits has a big potential in national and international markets. The cashew (Anacardium occidental L) is formed by a cashew nut (the true fruit), which is valued more in the international market in relation of its cavernous part (pseudofruto). The cashew juice, obtained from pseudofruto, produces a good quality of wine and vinegar. Therefore, these products can be a technically viable alternative and can minimize the waste of pseudofruto, as only 15% of the pseudo-fruit is taken advantage by the industries. Hence, a study of the kinetics of alcoholic and acetic fermentations for the production of cashew wine and cashew vinegar, respectively is made. In the production of the cashew wine, the mash was prepared with pseudofruit juice, having initial Brix value of 12,5°, while sucrose (common sugar) 210g/L and certain amounts of N and P nutrients were added. It was considered that the addition of the sucrose influenced the production of the ethanoJ. During the alcoholic fermentation up to 48 in the first step of fermentation (chaptalizacao) the concentration of sucrose decreased from 154.71g/L to 10.66g/L and in the second step from 176.28g/L to 86.84g/L. The amounts of alcohol, biomass, total acidity and pH values varied from: 7.9TGL to 99.76°GL; 15.5g to 37.5g 0,15 to 0,57g/100mL and 3.8 to 3.5 respectively up to 48 hours of the process. The alcoholic fermentation took place between 28°C and 33°C nad had received an inoculation of 20g/L of yeast (Saccharomyces cerevisiae). The process was conduted in a batch reactor with satisfactory production of alcohol, according to the standards required by the Brazilian legislation. In the acetic fermentation beckers of 600mL volume, at room temperature, were used. The yield of the alcoholic fermentation was 55.67% with efficiency of 74.17% and productivity of 1.41g/L.h. The values of the fermentation parameters: biomass (Yx/s), product (Yp/s) and the maximum growth velocity of the yeast were 0.064; 0.3 and 0.05b"1 respectively. In the acetic fermentation mashes that had higher initial concentrations of ethanol was more productive. With the purpose to optimize the cashew vinegar process a complete 2" factorial planning was realized The independent variables were initial concentration of ethanol in the cashew wine (3.0% to 6.0%,) and concentration of acetic acid (0.5% to 1.5% (first treatment). In the second treatment the initial concentration range of the acetic acid was changed to 1.0% to 2.0%, while the initial concentration range of ethanol was maintained same as in the first treatment. The yield and the productivity of the produced vinegars, during 72 hours, varied from 22% to 53.1% and from 0.19g/L.h to 0.42g/L.h (first treatment) and from 38.5%) to 86.2% and from 0.31g/L.h to 0.63g/L.h (second treatment), respectively. The application of the experimental planning helped to verify that the concentration of ethanol is a important variable as it influenced the yield as well as the productivity of the cashew vinegar.