Evolution of plant water status indices during butterhead lettuce growth and its impact on post-storage quality

BACKGROUND: The stage of maturity of perishable commodities has an important bearing on their quality and shelf-life. Lettuce is a highly perishable vegetable whose quality and shelf-life are influenced not only by its water content but also by its water status. The purpose of this study was to analyse the evolution of water status indices (relative water content, water content, free water, bound water and free water/total water ratio) during lettuce growth, their behaviour after storage (7 days at 0-2 degrees C and 97-99% relative humidity) and how they impact visual quality. To accomplish these objectives, several harvests were gathered (at different maturity stages) and water status indices and visual quality were analysed in both fresh and stored lettuces. RESULTS: As harvests were gathered in a more advanced state of maturity, a tendency of diminishment in the differences between values of outer and inner leaves was observed for all water status indices. Lettuces were able to retain high indices after storage only at final development stages. Sensory quality was higher in lettuces harvested at final development stages. Consequently, optimal maturity from the point of view of physiology and quality coincided with optimal weight and size for harvesting. CONCLUSION: The stage of maturity at harvest affected the sensory quality of lettuces, those harvested at later stages being the ones that best maintained their quality attributes after storage. (C) 2008 Society of Chemical Industry