Long Term Exposure to Low Ethylene and Storage Temperatures Delays Calyx Senescence and Maintains ‘Afourer’ Mandarins and Navel Oranges Quality

Nasiru Alhassan,Michael C Bowyer,Ron B H Wills,Penta Pristijono,John B Golding

doi:10.3390/foods8010019

Abstract

Calyx browning and internal quality loss are major physiological causes for the loss of quality in citrus fruit during storage. While the symptoms of calyx senescence are only superficial, it can affect the appearance and consumer acceptability of citrus fruit. In this study, continuous ethylene exposure at different storage temperatures was investigated to assess their effect on calyx senescence and internal qualities in ‘Afourer’ mandarin and Navel orange fruit during storage. ‘Afourer’ mandarin fruit were stored at ≤0.001 (equivalent to ethylene-free air), 0.01, 0.1 and 1 µL L−1 of ethylene at either 5, 10 or 20 °C, whilst in a parallel experiment, Navel oranges were exposed to ≤0.001, 0.1 and 1 µL L−1 ethylene at either 1 or 10 °C. Changes in external and internal postharvest quality parameters were assessed for up to 8 weeks for ‘Afourer’ mandarins and 10 weeks for Navel oranges. At all storage temperatures, high levels of ethylene were found to increase the level of calyx senescence, weight loss, loss of fruit firmness and respiration rates. Also, there were significant effects of ethylene and storage temperatures on total soluble solids (TSS) content, titratable acidity (TA), and ethanol accumulation in both citrus species. Continuous exposure to high ethylene also significantly reduced vitamin C and ferric reducing antioxidant power (FRAP) in ‘Afourer’ mandarins after 8 weeks of storage. Overall, ethylene treatments had a significant effect on both the external and internal qualities of the fruit during storage. The relationship between ethylene concentrations and storage temperatures demonstrate that lowering atmospheric ethylene levels at reduced storage temperatures maintain fruit quality during long term storage.

Highlights

Fruit appearance is an important aspect of consumer purchase and acceptability where the green fresh condition of the fruit calyx is a desirable consumer attribute of citrus appearance [1,2].Changes in the physical appearance of the calyx can occur as a result of either natural senescence or external stimuli such as heat stress, causing colour change, with abscission of the calyx
External fruit appearance is an important characteristic that influences consumer purchasing decisions. The results of these experiments showed a significant effect of both ethylene concentration and storage temperature (p < 0.001) on calyx browning during storage
No significant interaction was observed between ethylene concentration and storage temperature

Summary

Introduction

Fruit appearance is an important aspect of consumer purchase and acceptability where the green fresh condition of the fruit calyx (button) is a desirable consumer attribute of citrus appearance [1,2].Changes in the physical appearance of the calyx can occur as a result of either natural senescence or external stimuli such as heat stress, causing colour change (from green to yellow and brown), with abscission of the calyx. Retention of the calyx is important because it enhances cosmetic appeal, but it protects against fungal infection in the abscission zone of the fruit peduncle and extends fruit storage life [2]. Both mandarins and to a lesser extent oranges are susceptible to calyx senescence during storage. Citrus fruit can be stored for up to 8 weeks under optimal conditions, but storage life depends on pre-harvest conditions, cultivar and storage environment, where lower storage temperatures reduce fruit senescence [3]. Citrus fruit can be sensitive to chilling injury (CI) when exposed to chilling temperatures (

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