Chilling injury symptoms do not appear in nonripe peaches (Prunus persicu L.) while stored at low temperatures, but a dry-mealy texture (woolliness) appears in chili-injured fruits after ripening. Reduced pectinesterase and polygalacturonase activities were associated with reduced juiciness, reduced levels of water soluble pectins, poor texture and enhanced levels of insoluble pectins in peaches which were ripened after storage at 1°C for more than 3 wk. Pectinesterase and polygalacturonase activities and levels of pectic substances were unaltered in nonripened fruits held at 1°C. Fruits transferred to 20°C for 24 or 48 hr after 1 and 3 or 2 and 4 wk of storage at 1°C did not exhibit woolliness after 5.5 wk of storage. Warming for 12 hr was inadequate to prevent the development of woolliness. The effect of intermittent warming on providing a desirable texture in subsequently ripened fruits was related to enhanced pectmesterase and polygalacturonase activities. Low temperatures appeared to induce this physiological disorder by reducing the capacity to provide adequate levels of pectinesterase and polygalacturonase during subsequent ripening at nonchilling temperatures. Intermittent warming appeared to prevent injury by protecting the capacity to produce adequate levels of pectolytic enzymes during ripening.

Electrolyte leakage from tissue discs and internal conductivity of intact fruit of peach (Prunus persica (L.) Batsch) were determined during storage at 1°C and after transferring to 21°. Both methods produced similar results, however, the method used for measuring internal conductivity was rapid, nondestructive, and seemed to be more sensitive. Electrolyte leakage remained fairly constant while internal conductivity tended to decline during 5 weeks of chilling. Electrolyte leakage and internal conductivity increased when fruits were transferred to 21°. At 21° fruits which had been chilled for 2 weeks had enhanced leakage while conductivity was enhanced in fruits chilled for 1 and 2 weeks. In fruits transferred to 21° after 3 or more weeks of chilling, leakage and internal conductance declined and woolliness was concomitantly detected. The binding of free ions appears to be closely associated with woolliness in peaches.