This work studied the effectiveness of gaseous ozone disinfection on pummelo (Citrus Grandis L. Osbeck) fruit juice components. Unfiltered and filtered pummelo fruit juices were treated with gaseous ozone for up to 50 min with ozone concentration fixed at 600 mg/h. A microbiological and physicochemical properties analysis were conducted on the ozone-treated fruit juices samples. It was found that the survival rate of aerobic bacteria, yeast and mold in unfiltered pummelo fruit juice were higher compared to filtered juice, as the juice components acted as protective barriers to the microorganisms. The microorganisms' inactivation in pummelo fruit juices was also observed to have increased as the ozone treatment time increased. Significant effects on total colour difference, ascorbic acid content, and total phenolic content were also observed over increased ozone-treatment time. However, ozone was shown to be ineffective in activating PME activity in both types of juice. The experimental results of this study indicated that pummelo fruit juice components had significant effects on the effectiveness of gaseous ozone, however, the degree of the effects depends on the different fruit components (total soluble solids, total phenolic content). As a conclusion, filtered juice showed better quality characteristics in comparison to unfiltered juice post-ozone treatment.

The global fruit juice market is expanding alongside the exponentially growing demand for a healthy lifestyle. Fruit juice is a preferred drink among all age groups as it contains numerous essential nutrients that benefit human health. The safety aspects of fruit juice are equally important as its healthy features. The conventional method of thermal pasteurisation has been known to produce fruit juice of inferior quality. Hence, ozone is being considered as an alternative, non-thermal form of pasteurisation. With its strong oxidation potential, ozone exhibits antimicrobial characteristics and produces no toxic by-products. However, for ozone to be successfully adopted by juice producers, the synergistic effects of the composition of fruit juice and ozone treatment must be adequately evaluated. Therefore, the present work subjected various concentrations of Chokanan mango juice (MJ), diluted with distilled water (DW) at 100MJ:0DW, 75MJ:25DW, and 50MJ:50DW to aqueous ozone treatment at different ozone doses. The effects of these treatments on the physicochemical and antioxidant properties of the MJ were evaluated. Ozone was found to be effective in decreasing the pectin methylesterase (PME) activity arising from the de-esterification of the pectin molecules, and increasing the DPPH activity, thereby increasing the juice quality. Significant effects on the total colour difference (ΔE) and total phenolic content (TPC) were observed in proportion to the increases in ozone dose. The colour of the treated MJ was found to be positively correlated with the TPC, while a kinetic study was performed to investigate the proportionality of the colour and TPC degradation. The first-order reaction model fitted well with the degradation patterns of L* and b*, as well as the ΔE of the MJ samples. A significant difference was observed between the degradation rate constant (k-value) for the MJ samples, which suggested that the k-value could have been affected by not only the ozone dose, but also the juice matrix. The present work demonstrated that the composition of fruit juice was an essential intrinsic parameter that must be assessed before adopting ozone as a form of non-thermal pasteurisation to produce fruit juice which is stable in quality, and safe for consumption.