ROLE OF PECTINESTERASE AND POLYGALACTURONASE IN THE FORMATION OF WOOLLINESS IN PEACHES

ABSTRACT Chilling injury symptoms do not appear in nonripe peaches ( Prunus persica L.) while stored at low temperatures, but a dry‐mealy texture (woolliness) appears in chill‐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 pectinesterase and polygalacturonase activities. Low temperatures appeared to induce this physiological disorder by reducing the capacity to provide adequate levels of pectin‐esterase 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.