OPTIMISATION OF THERMAL PROCESSING PARAMETERS AND STORAGE DURATION OF TOMATO JUICE FOR ANTIOXIDANT RETENTION

Abstract

Tomato (Solanum lycopersicum) is a vegetable widely cultivated worldwide. It is known to be a rich source of antioxidants including carotenoids, vitamin C, tocopherol and phenolic compounds. These compounds have the ability to scavenge free radicals and also reduce oxidative stress. Industrially, tomato can be processed into various forms of products such as tomato juice, purees and paste. Extensive studies have been carried out to understand the kinetic changes in the nutritional and antioxidant quality of processed tomato products. The aim of this study was to optimise the processing parameters (temperature and time) as well as the length of storage of tomato juice for optimum antioxidant retention. In this report, tomato juice was thermally processed using different temperatures (55, 60 and 65oC) and time (3, 5 and 7 min) conditions. Thermally processed tomato juice samples were further stored for 7, 17.5 and 28 days. The Box-Behnken design of response surface methodology (RSM) was used to optimise the conditions for the production of tomato juice to have optimum antioxidant retention and 15 sample runs were generated. Changes in total carotenoid (TC), lycopene, vitamin C, vitamin E, total phenolic content (TP) and 2, 2’-azino-bis 3-ethylbenthiazoline-6-sulphonic acid (ABTS) scavenging activity were determined at different levels of sample runs. The experimental results were fitted to a second order polynomial equation derived from the multiple regression analysis of the data. Analysis of variance (ANOVA) was used to determine the model fitness and the significant effects of the factors and their interactions were tested at 95% confidence interval. The result showed that fresh tomato juice had TC, lycopene, vitamin C, vitamin E, TP and ABTS content of 91.32 mg/kg, 69.66 mg/kg, 39.04 mg/g, 2.0 mg/g, 0.66 mgGAE/g, 67.30 mgTEAC/g,