Nitrate Content in Minimally Processed Lettuce (Lactuca sativa L.) as Affected by Fluorescent Light Exposure During Storage

Abstract

Butter head lettuce (Lactuca sativa L.), a leafy vegetable commonly used in salads is characterized by its ability to accumulate high level of nitrate. Accumulation of nitrate in the edible part of the plant causes nitrate toxicity. Indeed, use of artificial light during storage, exploring new approach to prevent accumulation of nitrate. The objective of this study was to determine how light exposure during storage prevents accumulation of nitrate in butter head lettuce. Minimally processed lettuce in the form of leaf discs were stored in the dark and under fluorescent light at 5, 10 and 15 µmol m -2 s -1 at 10°C (95% RH) for 14 days. The light treatments were provided for 12 hour's photo period. Light exposure during storage significantly prevented nitrate accumulation, delayed degradation of chlorophylls and extends shelf life. In contrast in the darkness, nitrate content was accumulated while chlorophyll level was degraded. The delayed accumulation of nitrate under light can be because of the higher accumulation of soluble sugars, as changes in nitrate level and soluble sugar were found reverse. In conclusion, light exposure in the level applied successfully prevented nitrate accumulation, increasing the level of soluble sugars and delayed loss of chlorophyll pigment.