The Different Concentrations of Citric Acid on Inhibition of Longkong Pericarp Browning during Low Temperature Storage

Abstract

Longkong is one of the nutritious and economical fruits in Thailand. It has a very short shelf life due to its severe pericarp browning at ambient temperature storage. In the present study, the different concentrations (1, 2, and 3%) of citric acid were used to control longkong pericarp browning during storage at 18°C and an 85% relative humidity. Longkong treated with distilled water served as a control. An increased pericarp water loss and decreased fruit respiration rate was observed throughout the storage. Fruit pericarp ultrastructural observation showed the severe damage on the pericarp parenchymal tissues during at the end of storage. The different concentrations of citric acid effectively limited longkong pericarp browning throughout storage. Longkong treated with 3% citric acid significantly suppressed the increase of pericarp pH, phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD) activities, and loss of pericarp total phenolics as compared to a low concentration and control fruit (P < 0.05). These findings have suggested citric acid is a promising agent that controls longkong pericarp browning and oxidoreductase activities during prolonged storage.