Effects of Pure Oxygen on the Rate of Skin Browning and Energy Status in Longan Fruit
Xingguo Su1, Yueming Jiang1*, Xuewu Duan1, Hai Liu1, Yuebiao Li1, Wenbin Lin1 and Yonghua Zheng2
1Institute of Economic Botany, South China Botanic Garden, The Chinese Academy of Sciences, Guangzhou LeYiJu 510650, PR China
2College of Food Science and Technology, Nanjing Agricultural University, Nanjing WeiGang 210095, PR China
Article history:
Received January 1, 2005
Accepted April 8, 2005
Key words:
browning, longan (Dimocarpus longan Lour.), energy, peroxidase, polyphenol oxidase, pure oxygen, respiration
Summary:
Postharvest pericarp browning is one of the main problems resulting in reduced shelf life of longan fruit. Experiments were conducted to examine the changes in concentrations of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP), energy charge levels and activities of polyphenol oxidase (PPO) and peroxidase (POD) in relation to pericarp browning of longan fruit. Fruit kept for 6 days in pure oxygen atmosphere at 28 °C showed lower browning indices and higher ATP concentrations but lower AMP concentrations and higher respiratory rates, compared to those kept in air. While energy charge decreased during storage, the decrease was delayed markedly by exposure to pure oxygen. There was a lower energy charge in the browned fruit, which was associated with rapid increase in malondialdehyde concentration. Enhanced respiration of longan fruit exposed to pure oxygen can result in the production of ATP. However, fruit exposed to pure oxygen exhibited higher activities of PPO and POD, which was not associated with reduced skin browning inhibition. These results supported the hypothesis that skin browning of postharvest longan fruit may be a consequence of membrane injury caused by the lack of maintenance energy.
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