Acidic electrolyzed oxidizing water delayed the breakdown occurrence in pulp of fresh longan by regulating the metabolisms of respiratory and energy

Abstract

The efficacy of acidic electrolyzed oxidizing water (AEOW) treatment on the respiratory and energy metabolism during storage of harvested longan and its relationship with pulp breakdown were investigated. Results confirmed that the AEOW treatment exerted a significant inhibitory effect on longan pulp breakdown, with 15.5 % lower pulp breakdown index than the control at 6 d. Compared to the control fruit, the AEOW treatment displayed lower activities of polyphenol oxidase (PPO), ascorbic acid oxidase (AAO), alternate oxidase (AOX), cytochrome C oxidase (CCO), succinate dehydrogenase (SDH), pulp phosphohexose isomerase (PGI), and higher levels of nicotinamide adenine dinucleotide kinase (NADK), glucose-6-phosphate dehydrogenase (G-6-PDH) and glucose-6-phosphate dehydrogenase (6-PGDH). Furthermore, the AEOW treatment increased the amount of NADPH and NADP while decreasing that of NADH and NAD. In terms of energy metabolism, the AEOW treatment maintained higher levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP), energy charge, H+-ATPase, Ca2+-ATPase, and Mg2+-ATPase, but lower content of adenosine monophosphate (AMP). Therefore, the AEOW treatment inhibited respiratory metabolism by decreasing the terminal oxidase activities, tricarboxylic acid cycle (TCA cycle) and glycolytic pathway (EMP), and increasing the pentose phosphate pathway (PPP), which helped to maintain a higher energy status and further led to attenuation of longan pulp breakdown.