Physiological factors associated with overripeness, internal breakdown and gel breakdown in plums stored at low temperature

Abstract

Plums (Prunus salicina cv. Songold) were stored at -0.5°C for up to 50 d. On the day of harvest and thereafter at ten-day intervals, sub-samples were stored at 15°C and allowed to ripen for eight days, with evaluations every two days. Low temperature storage prior to ripening at 15°C was a prerequisite for plums to ripen. Overripeness was inhibited by low- temperature storage but developed when fruit was ripened at, or before, 30 d of storage. Longer storage resulted in the development of gel and internal breakdown at both -0.5°C and during ripening. The transition from overripeness to gel and internal breakdown was associated with significant increases in electrolyte leakage and internal conductivity at a time that viscosities of water soluble pectins were high. The resulting decrease in extrac- table juice suggested that cell fluids which leaked through cell membranes had bound with pectic substances. This was associated with development of gel and internal breakdown.