Effects of environmental conditions and ripeness of the fruit at harvest on the physicochemical quality and internal skin browning of cold-stored ‘Mollar de Elche’ pomegranate

Abstract

Pomegranate is a cold-sensitive fruit, prone to develop chilling injury (CI) which manifests as external pitting and internal browning. In the case of ‘Mollar de Elche’ pomegranates, storage at 5 °C and >90% relative humidity (RH) is recommended to minimize CI, weight loss, and fungal diseases. However, in recent seasons, increased internal skin browning has been observed, in the absence of typical external CI symptoms. Furthermore, this disorder becomes apparent after a few weeks of storage under optimal conditions. The objective of this work was to study the effects of environmental conditions at harvest (early in the morning (E) with mild temperatures and late in the morning (L) with maximum solar radiation) and harvest date (at the beginning (H1) and the end (H2) of the growing season 2022) on the physicochemical quality and internal tissue browning of ‘Mollar de Elche’ pomegranates stored for 8 and 12 weeks at 6 ºC and 90-95% RH, followed by 7 days at 20 ºC and 85% RH. Differences in solar radiation, ambient temperature and RH at harvest time resulted in fruit temperatures of 15.7±1.8 and 28.1±0.4 ºC for E and L, respectively. No significant differences in internal browning were observed between E and L harvest time, whereas H2 fruit were less susceptible than H1 fruit. Furthermore, fruit with higher internal browning incidence showed higher respiration, weight loss, and electrolyte leakage, indicating damage of the cell membrane. Fruit firmness was greater in H1 than H2 at harvest and after 8 weeks of cold storage plus shelf life, but no differences were observed between treatments at the end of storage. Overall, late-harvest fruit was less susceptible to internal browning. Future work should explore the origin of this physiological disorder and feasible postharvest management to minimize it