Postharvest storage of loose leaf lettuce (Lactuca sativa); the role of light, nutrients, bioactive levels and potential health benefits

Abstract

A diet rich in fresh fruit and vegetables is associated with a reduced incidence of disease, this health benefit is largely due to bioactive compounds. Bioactive compounds are mostly secondary metabolites, many of which help to protect plants during times of stress. Most vegetables are stored in the dark postharvest and this can induce senescence, which often results in a loss of bioactive compounds. By improving postharvest storage techniques, the loss of bioactive compounds could be reduced. The aim of this study was to investigate how storage in the light, supplied by full spectrum light emitting diodes (LED’s), affected the postharvest storage life and bioactive molecule content of loose leaf lettuce (Lactuca sativa). In addition, how storage of lettuce in the presence or absence of light influences the bioprotective capacity simulated human digests of lettuce leaves have on cultured Caco-2 cells was also investigated. Lettuce plants were stored in either constant darkness, a photoperiod (8 h light: 16 h dark), or in constant light. Plants stored in the photoperiod had a greater antioxidant capacity than plants stored in either constant darkness or constant light. Lettuce plants stored in constant light were shown to be under oxidative stress and this negatively influenced both measures of quality and human cell bioprotective capacity, compared to plants stored under a photoperiod. The results of this study highlight a simple technology that enables both more bioactive compounds and a greater human cell bioprotective capacity to be retained during postharvest storage of lettuce. This could potentially be of benefit to human health.