Pre-storage temperature conditioning reduces cortex browning and cavity and alters organic, amino, and fatty acid metabolism in cold-stored ‘Chuhwangbae’ pears

Abstract

‘Chuhwangbae’ pears are susceptible to internal disorders thought to be related to abiotic physiological chilling stress during cold storage. For this cultivar, pre-storage warm temperature conditioning (e.g. gradual or step-down of fruit temperatures) after harvest is highly recommended to control the development of postharvest storage disorders during cold storage. This pre-storage temperature conditioning at relatively warm temperatures relative to final storage temperature is also called “ambient temperature” conditioning by fruit packinghouse personnel. This study evaluated the influence of pre-storage ambient temperature conditioning duration (holding fruit at 22 °C) on ‘Chuhwangbae’ pear fruit quality including the incidence of physiological disorders and metabolic responses related to these disorders during cold storage. Postharvest pre-storage temperature conditioning (1, 2, 3, or 4 weeks at 22 °C) reduced cortex lightness and flesh firmness, and increased fruit weight loss and shrivelling during cold storage. The incidence and severity of cortex browning and cavity were reduced by pre-storage temperature conditioning. Pre-storage temperature conditioning reduced glucose, sorbitol, and fumaric acid contents after cold storage. Phenylalanine, isoleucine, and valine contents decreased with pre-storage temperature conditioning, but methionine, glutamine, and proline contents were higher in conditioned fruit than in unconditioned fruit. In addition, oleic acid content and the ratio of unsaturated fatty acid to saturated fatty acid were reduced by pre-storage temperature conditioning during cold storage. Results indicate that pre-storage temperature conditioning reduces incidence of cortex browning and cavity in part by altering cell wall metabolism during cold storage. Concurrently, pre-storage temperature conditioning reduces metabolites that are substrates for primary metabolism (glucose, sorbitol, and fumaric acid) and for volatile metabolism (isoleucine and valine), which corresponded to other aspects of fruit quality negatively affected by pre-storage temperature conditioning.