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Ascorbic acid occurs naturally in many wine-making fruits. The industry also uses ascorbic acid as an antioxidant and color stabilizer in the making of alcoholic beverages including white wine, wine cooler, alcopop, and fruit liqueur. However, the degradation of ascorbic acid itself may cause browning and the deterioration of color quality. This study was aimed to monitor the degradation of ascorbic acid, the formation of degradation products, and the browning in storage of ascorbic acid containing 0-40% (v/v) ethanolic solutions buffered at pH 3.2 as models of alcoholic beverages. The results show that ascorbic acid degradation in the ethanolic solutions during storage follows first-order reaction, that the degradation and browning rates increase with the increase of ethanol concentration, that the activation energy for the degradation of ascorbic acid is in the range 10.35-23.10 (kcal/mol), that 3-hydroxy-2-pyrone is an indicator and a major product of ascorbic acid degradation, and that aerobic degradation pathway dominants over anaerobic pathway in ascorbic acid degradation in ethanolic solutions.

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Raw whole strawberries, if contaminated with pathogens, such as Escherichia coli O157:H7, must be pasteurized prior to consumption. Therefore, the objective of this research was to investigate the thermal inactivation kinetics of E. coli O157:H7 in strawberry puree (SP), and evaluate the changes in anthocyanins and color, and the survival of yeasts and molds (YM) after thermal processing. Inoculated with a 5-strain cocktail, fresh SP, with or without added sugar (20 and 40 °Brix), was heated at 50, 52, 54, 57.5, 60, and 62.5 °C to determine the thermal resistance of E. coli O157:H7. In raw SP, the average D-values of E. coli O157:H7 were 909.1, 454.6, 212.8, 46.1, and 20.2 s at 50, 52, 54, 57.5, and 60 °C, respectively, with a z-value of 5.9 °C. While linearly decreasing with temperature, the log D-values of E. coli O157:H7 increased slightly with sugar concentration. The log degradation rates of anthocyanins increased linearly with temperature, but decreased slightly with sugar concentrations. These results suggest that sugar may provide some protection to both E. coli O157: H7 and anthocyanins in SP. The browning index was not affected by heating at 50 and 52 °C at low sugar concentrations, but increased by an average of 1.28%, 2.21%, and 10.1% per min when SP was exposed to heating at 54, 57.5, and 60 °C, respectively. YM was also inactivated by heating. This study demonstrated that properly designed thermal processes can effectively inactivate E. coli O157:H7 and YM in contaminated SP, while minimizing the changes in anthocyanins and color.

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