ICE-TEMPERATURE STORAGE COMBINED WITH STAGE-WISE SO₂ RELEASER TREATMENT EXTENDED SHELF LIFE OF LONGAN FRUIT

Longan fruit are highly perishable when stored at ambient temperature. SO₂ treatment has been widely used to inhibit pericarp browning of longan fruit yet entails the risk of high SO₂ residue in aril. Our previous study indicated that stage-wise SO₂ releaser treatment reduced SO₂ residue in aril of longan fruit. Ice-temperature storage has the potential to maintain the quality of the fruit aril, but results in severe pericarp browning. In the present study, ice-temperature combined with stage-wise SO₂ releaser treatment (ITS) was applied to the storage of longan fruit. The pericarp color, physiological change and fruit quality were investigated. Compared to control fruit in traditional 3°C storage, the pericarp color of the ITS-treated fruit maintained a fresh-green appearance, which was represented by the high level of b, C and L values and a high content of yellow pigments. After 48 days, a higher good fruit rate of 91.15% was achieved for ITS-treated fruit, when compared to the control fruit with 0% good fruit rate. ITS remarkably inhibited the activity of PPO and POD, and decreased pH value of fruit pericarp. A lower SO₂ residue with 29.2 mg/kg in aril was detected in ITS-treated fruit compared to SO₂-treated fruit. Taken together, these results suggested that ITS is a practical technique for extending shelf life of longan fruit.