Leaf water status evolution during greenhouse butterhead lettuce storage under adverse humidity conditions was evaluated. The relationships between water status and the chlorophyll content and overall visual quality (OVQ) were analysed. Parameters were evaluated in external, middle and internal sections of the lettuce heads. Indices showed different behaviour in different sections. There was a continuous decrease in the relative water content (RWC) in all sections. Decrement in water content (WC) was significantly higher in external section than in other sections. Increases were observed in bound water (BW) in all sections, probably representing a vegetable physiological response in order to control the amount of water loss. Chlorophyll in external section decreased following a first order kinetic. In external section, all parameters correlated with OVQ showing WC and RWC the highest correlation index; for middle section OVQ correlated with WC, RWC and free water (FW) while for internal section correlated only with WC.
Keywords: butterhead lettuce, leaf water status, chlorophyll degradation, overall visual quality, OVQ, shelf life, postharvest technology, lettuce sections, humidity levels, quality indices, greenhouse storage