Effect of storage regimes on pectolytic enzymes, pectic substances, internal conductivity and gel breakdown in cold stored ‘Songold’ plums

Abstract

SummaryPlums (Prunus salicina cv. Songold) were cold stored according to a single-temperature regime comprising 28 d at −0.5°C, and a dual-temperature regime comprising 10 d at −0.5°C followed by 18 d at 7.2°C. After cold storage, the plums were ripened for 8 d at 10°C. Pectolytic enzyme activity, pectic composition, internal conductivity and gel breakdown were determined at seven stages during storage and ripening. Although not exposed to chilling temperatures prior to harvest, approximately 10% of the plums exhibited gel breakdown at harvest, indicating that the disorder cannot be classified solely as a cold-storage chilling disorder. The higher temperatures of the dual-temperature regime resulted in higher polygalacturonase activity than with the single-temperature fruit. Consequently, protopectin degradation and the concomitant production of water- soluble pectins were greater in the dual-temperature fruit. Single-temperature storage resulted in higher pectinmethylesterase activity during the latter s...