Impact of Non-Thermal Processing on Antioxidant Activity, Phenolic content, Ascorbic Acid content and Color of Winter Melon Puree

In the last decade, non-thermal processing for inactivating microorganisms has been developed in response to the worldwide interest for more fresh and improved quality of food products. Winter melon is a very perishable fruit, hence, processing into puree is a necessity. However application of heat in the production of puree could affect the nutritional values, thus, application of non thermal treatment in combination with preservation method is significant for this fruit. This study was conducted to evaluate the effect of non-thermal processing in combining with preservation method on antioxidant activity, level of key antioxidant groups (total phenolic and ascorbic acid content) and the color of winter melon puree. Total phenolic content (TPC) was measured using Folin-Ciocalteu reagent. Ascorbic acid (AA) was determined using 2,6-dichlorophenol-indophenol titration method. Antioxidant activity were determined using four antioxidant assays namely Ferric Reducing Antioxidant Potential (FRAP), Oxygen Radical Absorbance Capacity (ORAC), 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and β-Carotene Bleaching Assays. For the TPC, puree with pH 3 (28.5±1.3 GAE/g fresh weight) exhibited high in TPC as compared to puree with pH 3.5 and unprocessed puree. In contrast, unprocessed puree contains significantly high ascorbic acid (AA) content (35.9 ± 1.8 mg/100 g fresh mass) as compared to pH 3.0 and pH 3.5 purees. In general, antioxidant activity for all assays of pH 3.0 and pH 3.5 purees were significantly higher (p<0.05) than unprocessed puree. Color changes (ΔE) were not significant between puree with pH 3.0 and pH 3.5. Therefore, processed winter melon puree using non-thermal processing in combination with chemical preservation method could be an efficient method to preserve the quality of winter melon puree more superior than unprocessed puree.