Vol. 69 No: 3

Title:
Effect of Storage Regimes on Pectolytic Enzymes, Pectic Substances, Internal Conductivity and Gel Breakdown in Cold Stored ‘Songold’ Plums

Authors:
M.A. TAYLOR, E. RABE, M.C. DODD and G. JACOBS

pp: 527-534

Abstract:
Plums (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 stages of storage and during ripening. Increases in temperature after 10 d and 28 d in dual- and single-temperature fruit, respectively, were associated with significant increases in the viscosity of water-soluble pectins, internal conductivity and gel breakdown. The significant positive correlation between internal conductivity and gel breakdown suggested that membrane integrity is closely associated with development of gel breakdown.

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