Effect of pectin methyl esterase and Ca2+ ions treatment on antioxidant capacity, shelf-life and quality of minimally processed pomegranate (Punica granatum L.) arils.

Abstract

Pomegranate fruits are difficult to peel and once peeled, extracted arils have very short shelf-life. Therefore, present investigation was carried out to extend the shelf life of minimally processed pomegranate arils using pectin methyl esterase (PME) and CaCl2 treatment during refrigerated storage. The arils of freshly harvested pomegranate fruits (Punica granatum L.) were treated with different concentrations of food-grade PME (50-300 units) and calcium ions (0.5-2.0 % as CaCl2) for a period of 5-30 min using response surface methodology. Treated and untreated arils were then packed in low density polyethylene bags (25μ) and maintained under low temperature (5oC; 90% RH) for evaluating the physical, biochemical and microbial quality of pomegranate arils at four days interval. Physiological loss in weight increased during storage but no food-borne pathogens were found during 28 d of cold storage in treated arils. Color and firmness of both treated and untreated arils decreased during storage but it was better maintained in treated arils. The firmness was found to be 0.630 N in treated samples compared to untreated one (0.511 N) after 20 d of storage. Total antioxidant capacity, ferric reducing antioxidant power, polyphenol oxidase and lipoxygenase activities increased during storage. The treatment with 249.33 units of PME and 1.70 % CaCl2 for an immersion time of 24.93 min was found to be most effective treatment for maintaining the quality of minimally processed arils for longer period. Sensory score was also higher in treated pomegranate arils that were quite acceptable even after 20 d of referigerated storage as against 12 d for untreated ones.