Post-harvest melatonin application reduced browning in minimally processed lettuce (Lactuca sativa L.) during low temperature storage

The investigation was carried out to assess the effect of post-harvest dipping of minimally processed fresh cut lettuce with various concentrations (10, 100 and 1000 μmolL-1) of melatonin on shelf-life and sensory quality of lettuce stored at 6±2ºC for 8 days. Melatonin treatment was found effective in maintaining freshness and sensory quality of lettuce during storage. Browning was reduced by 45% and visual quality index increased by 44.10% compared to control in 100 μmol L-1 melatonin treated samples on the 6th day of storage. Maximum total chlorophyll, total phenol and total antioxidants and least activity of browning related enzyme i.e., peroxidase (POD) was observed in 100 μmol L-1 melatonin treated samples during storage. No significant variation was observed between 10 μmol L-1 melatonin treated and control samples. Browning index value had significant negative correlation with total chlorophyll, total phenol and total antioxidants whereas POD activity had significant positive correlation. It can be inferred from the present investigation that post-harvest treatment of 100 μmol L-1 melatonin extended shelf-life of minimally processed lettuce for 6 days by preserving phenols, chlorophyll, antioxidants and inhibiting POD activity.