Browning inhibition and quality preservation of fresh-cut romaine lettuce exposed to high intensity light

Fresh-cut romaine lettuce (FRL) is susceptible to tissue browning and quality deterioration, and thus has short shelf-life. The effect of continuous high intensity light (NIL, 2500 lx), low intensity light (LIL, 500 lx), and darkness on FRL browning and quality was studied upon 7 d cold storage. Changes in browning index (BI), browning-related enzyme activity, quinone, total phenol (TP), ascorbic acid (AA) content, antioxidant capacity (AC), and fresh weight loss were investigated. HIL significantly decreased BI and inhibited polyphenol oxidase (PPO) and peroxidase (POD) activities, and quinone accumulation. While HIL preserved more TP and AA content and resulted in higher AC value compared to darkness. Conversely, LIL induced PPO and POD activities as well as quinone generation, resulting in higher BI compared with darkness. Meanwhile, LIL induced low both TP content and AC value that contributed to low quality property. Both HIL and LIL notably increased PAL activity and fresh weight loss that progressively increased over time compared to darkness. Conclusively, HIL exposure effectively protected FRL from browning and quality decay by inhibiting browning-related enzyme activity and maintaining nutritional constituents during refrigeration. Industrial relevance: Romaine lettuce is consumers' favorite leafy vegetable for its crispness, good aroma, tender appearance as well as high phytochemicals like phenolic compounds. However, by nature, romaine lettuce is very perishable and susceptible to quality decay and enzymatic browning. In current retail marketing, fresh-cut produce is unavoidably exposed to light conditions during its displayed shelf-life for consumers' choice. This study investigated the effect of continuous high intensity light, low intensity light exposure and darkness on tissue browning and quality property of fresh-cut romaine lettuce. Result indicated that the high intensity light exposure was effective in inhibiting tissue browning and maintaining quality of fresh-cut romaine lettuce upon cold storage. The findings are innovative and very helpful for fresh-cut lettuce producers, distributors, and sellers to decrease the occurrence of undesirable color and nutrition changes by modifying light illumination during storage. (C) 2012 Elsevier Ltd. All rights reserved.