Impact of ozone treatment on the physico-chemical properties, bioactive compounds, pectin methylesterase activity and microbiological properties of watermelon juice.

The increasing consumer demand for higher quality fruit juices has encouraged the use of non-thermal processing to extend the shelf life of perishable juice, watermelon juice. Ozone with its high oxidizing effect serve as an effective non-thermal processing treatment. The aim of this study was to investigate the impact of ozone treatment on the physico-chemical, bioactive compounds, pectin methylesterase (PME) activity and microbiological properties of unclarified and clarified watermelon juice. The ozone gas was pumped into watermelon juice for up to 25 min in a closed chamber. The microorganism inactivation in unclarified and clarified watermelon juices improved across the increasing processing time. Among these juices, the microorganism inactivation efficiency of ozone was found higher on clarified juice (3.466 log) than unclarified juice (3.150 log). It was found that °Brix value and PME activity were not altered by ozone treatment. The other physico-chemical properties (titratable acidity, pH, total colour difference, non-enzymatic browning, cloudiness) and bioactive compounds reduced across processing time. This study demonstrated that ozone treatment is an effective non-thermal processing technique to reduce the microorganism in watermelon juice. Further study is required to optimise the processing parameters of ozone treatment to maintain the overall quality of the watermelon juice.