Effects of supercritical carbon dioxide and thermal processing conditions on phenolics, antioxidant activity, and yeast inactivation in muscadine and pomegranate juice
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Muscadine juice and pomegranate juice were processed with two pasteurization methods, supercritical and thermal processing, to determine their effects on antioxidant activity (ORAC) and total phenolics (TPC) retention. The thermal processing conditions used were 50-80°C and 1-30 min. Supercritical conditions varied between 35-55°C, 20.7-34.5MPa, and 10-30 min. With thermal processing temperatures greater than 60°C, phenolics and ORAC values in muscadine juice began to decrease while pomegranate juice phenolics did not show any reductions until 70°C. By filtering particulates after thermal treatment, phenolics and ORAC retentions increased by at least 8% compared to unprocessed juice. The supercritical processing conditions of 45°C, 27.6MPa, and 20 min had the greatest phenolics and ORAC retentions. These conditions increased the phenolics and ORAC retentions in both muscadine and pomegranate juice by 1.2-1.9% compared to the unprocessed juice. In muscadine juice, supercritical processing achieved a 3-4 log reduction in Zygosacchromyces bailii.