Study On The Technology Of Controlled Atmosphere Storage And Its Mechanism In Longan Fruits

In this study, we used Fujian's famous 'Oolongling' longan to carry out an experiment employing the Controlled Atmosphere equipment made in Italy. Compared with the regular cold storage (i.e., (2.5±0.5)℃ and 90%~95%RH) , the effects of the atmosphere composition ( (4±0.5% ) O2, ( 3±0.5% ) CO2 ) and different concentrations of biology inhibitors (i.e., thiourea and L-cysteine) on the browning of longan pericarp, enzyme activity(PPO, POD, SOD and CAT)and storage quality were studied. The results are showed as follows:1. Compared with the regular cold storage, CA significantly lowered the activities and delayed the rise of PPO and POD in longan pericarp; kept greater SOD and CAT activities; postponed the increase of MDA content and cell membrane permeability of pericarp; reduced the respiratory intensity of fruit and decomposition of pericarp pigment; maintained the total soluble solids, titratable acid and vitamin C contents, decreased the index of pericarp browning and the rate of fruit decay and postponed senescence, thereby the shelf and storage life of the fruit was improved.2. With CA, different concentrations of thiourea (0.5%, 1.5% and 2.5%) and L-cysteine (0.01%, 0.05% and 0.1%) displayed some effects on color and freshness preservation on longan. Thiourea (1.5% and 2.5%) and L-cysteine (0.05% and 0.1%) considerably reduced the activity and rise of PPO and POD activities in longan pericarp; kept greater SOD and CAT activities; postponed the increase of MDA content and cell membrane permeability of pericarp; decreased the index of pericarp browning and the rate of fruit decay, postponed senescence, thereby the shelf and storage life of the fruit was improved. However, the effect of restraining the respiratory intensity of longan fruits was not obvious. This indicates that respiratory intensity of longan fruits mainly depends on temperature and atmosphere composition.3. With economic consideration, 2.5% thiourea and 0.05% L-cysteine for biology inhibitors to suppress the browning of longan pericarp is suggested for commercial purposes.Mechanisms under which CA and biology inhibitors are capable of retarding senescence and decreasing the browning of longan pericarp are discussed .