Inhibition of Pericarp Browning and Phenolics Oxidation in Longan (Dimocarpus longan Lour.) Fruit during Controlled Atmosphere Storage

Longan fruit cv. Daw at the commercial ripe stage were held in controlled atmosphere (CA) chambers applied with 2 or 4 kPa O-2 plus 5 or 15 kPa CO2 (balance nitrogen) or air (control) at 4 degrees C with 95% relative humidity. CA levels in 2 kPa O-2 treatments were effectively inhibited pericarp browning relative to the control, whilst 4 kPa O2 treatments were not consistently better than the control. Polyphenol oxidase (PPO) activity correspondingly decreased resulting to reduced phenolics oxidation indicated by retention of higher phenolics content than that in air. Phenylalanine ammonia lyase (PAL) also decreased and may have contributed to the reduction of browning. Most effective CA level was 2 kPa O-2 plus 15 kPa CO2, retarding browning by 10 days. However, pulp ethanol content increased in CA-stored fruits.