Abusive Isothermal Conditions Inmediatly after Harvest afect Butterhead Lettuce Water Status

Abstract

The purpose of this study was to evaluate water status and overall visual quality (OVQ) of fresh butterhead lettuce during the first hours after harvest when plants were exposed to three different isothermal conditions: T1 = 0–2C, T2 = 10–12C and T3 = 20–22C (all with optimal relative humidity). Relative water content (RWC), water content (WC), free water (FW), bound water (BW), free water-to-total water ratio (FW/TW) and OVQ were evaluated in external (E),middle (M) and internal (I) zones of lettuce. High temperatures affected the tissue response to the uptake of water, diminishing the tissue turgid mass and increasing RWC, being I the most affected zone. Water movements (decreases in FW with simultaneous increases in BW) were detected immediately after harvest, even if conditions were optimum. However, the exposition temperature was a significant factor that affected the exchange between FW and BW. Texture and browning of lettuce heads were affected by inadequate temperature.