Optimization of thermal processing condition for winter melon puree using response surface methodology

Winter melon is a perishable fruit, hence, the need to process it into puree is a necessity. The concept of thermal processing involves in canning process as the most widely used method of preserving and extending the shelf life and capable to inactivate pectinmethylesterase enzyme (PME) in fruit puree was studied. The purposes of this study are to determine the optimum temperature and time for thermal processing of winter melon puree (WMP) and to verify the optimum condition proposed by response surface methodology (RSM). Winter melon puree samples was treated at thirteen different treatment combinations of temperature (°C) and time (second). Each treatment of WMP was analysed for the percentage (%) reduction of PME, total phenolic content (TPC), percent pulp content and physicochemical analysis such as colour (absorbance), total soluble solid (°Brix) and pH. PME and TPC were the responses used in this research. For each treatment % reduction of PME ranged from 27.61-78.05 % while TPC ranged from 12.21-28.84 mg GAE/g fresh weight. The % of pulp content for each treatment of WMP varies from 51.17-63.17 %. However, there were no significance difference results in the colour, total soluble solid and pH of WMP samples. The MINITAB software version 15 used for optimization suggested three possible optimum conditions but the best desirability where the experiment was feasible at temperature 84.5 °C and time 94.1 seconds. At this optimum treatment, the predicted value of % reduction of PME was 78.87 % and TPC 20.34 mg GAE/g fresh weight. After verification at the optimum treatment, results showed that % reduction of PME was 78.12 % and TPC was 20.43 mg GAE/g fresh weight and since the difference values between predicted and verification for both responses (PME and TPC) are less than 5% meaning that the optimum condition predicted by RSM of MINITAB software version 15 can be accepted at the 5% level of significant difference. At this condition pH o- WMP was 4.76, colour absorbance 0.4124 nm, % pulp content 55.0 % and total soluble solid 1.282° Brix. All derived mathematical model for the response was found fit significantly to predict the data. This study showed that RSM does not only reduce the number of experiment to be carried out but also effective tool in determining the optimum condition of thermal treatment for WMP.