Lotus flower extract as a natural anti-browning agent for fresh romaine lettuce (Lactuca sativa L. var. longifolia)

Abstract

The effect of lotus (Nelumbo nucifera Gaertn.), butterfly pea (Clitoria ternatea) and Siam tulip (Curcuma sessilis) aqueous extract on reduction of polyphenol oxidase (PPO) and peroxidase (POD) in romaine lettuce (Lactuca sativa L. var. longifolia) were evaluated. Results showed that in vitro lotus flower aqueous extract exerted the highest reduction of PPO and POD activities on the romaine lettuce. The effectiveness of in vivo application of lotus flower aqueous extract to control browning cut stem ends of fresh romaine was examined. Romaine lettuce harvested as a whole plant and cut off at the stem. Cut stem ends of romaine lettuce were dipped in various concentrations of lotus flower extract for 5 min and packaged in polypropylene plastic bags. Weight loss, color, browning index as well as PPO and POD activities were evaluated during 12 days of storage at temperature of 10±2°C and relative humidity 50±5%. Cut stem ends dipped in 0.5% aqueous extract of lotus flower resulted in inhibition of browning of cut stem ends and decrease in PPO and POD activities. Thus, exogenous 0.5% aqueous lotus flower extract treatment could be a useful application to alleviate browning in cut stem ends of fresh romaine lettuce.