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Abstract
The effect of micro-oxygen (MO) and atmospheric processing on polyphenol oxidase (PPO) in bananas and orange juice quality was evaluated. PPO activity decreased non-linearly with decreasing oxygen concentration from 198 Units/ml to 45 Units/ml, at atmospheric and micro-oxygen (8ppm) concentrations. The decrease of PPO activity followed a second order polynomial regression (R2>0.9). There were no quantifiable differences between Raman spectra taken on the PPO extracts at different times and different oxygen concentrations. A decreased in absorbance at longer times of assay was observed, and may be an indicative of non-Henri-Michaelis-Menton kinetics. Dissolved oxygen (DO) in orange juice processed under MO was low and consistent (34ppb to 100ppb) and not statistically different from juice processed under atmospheric conditions (92ppb to 200ppb) (p<0.05). The shelf life studies performed suggest that there are no significant differences in vitamin C retention and browning for juices processed under both conditions (p<0.05).