Study On The Preservation Of Longan Fruits By Coating

Longan(Dimocarpus longan Lour.) is a special fruit in south China as well as in Fujian. However longan will metabolize vehemence, lose moisture and browning because longan mature in the hot and humid period of the year, which influence the storage and distribution of longan. Therefor it is important to do research of the storage technology of the longan. In order to studying Knojac and sulfur management in longan storage in the room temperature, qualitative analysis of longan were studied in this thesis, so as to find the parameter and method which can adapt to the longan storage. The results are showed as follows:(1) Coating could significantly reduce water loss rate, respiration, dissolvable substance loss, total acid loss,it can also protect Vc.(2) The effect of the application of several coating material to longan well.The result showed that coating with Konjac can reduce the physiological reaction, avoid anaerobic respiration. During the storage period,the heathy fruit rate reach 75%, water loss rate, respiration were reduced significantly and the dissolvable substance loss, total acid loss, Vc can be well protected.(3)Sulfur management can elevate the healthy fruit rate. The result showed that proper concentration of sulfur can restrain the pericarp browning, ameliorate the pericarp appearance, enhance the commodity value.(4) Sulfur management can be conbined with coating which can strengthen the freshkeep effect. The effect of coating with 4% Na₂SO₃+0.2%Knoajc is better than using Na₂SO₃ separately. The conbining of sulfur and coating can prolong the period of time of reaction.(5)The concentration of the sulfur and the reaction time can influence the effect of storage directly, which can also influence the SO₂ residue of the longan flesh. In order to find the optimal combination of the two factor, the index of the thesis is healthy fruit rate and find out the relation between the concentration and reaction time, the equation was also educed. The optimal combination is that: the concentration of sulfur is 4.66%, the reaction time is 8.9 minute, in the condition the healthy fruit rate can reach 93.43%.(6) The parameters gained from the equation were applied in the longan storage experimentation. The result showed that: in that condition the SO₂ residue of the longan flesh was lower than state standard. The index of cell membrane permeability of longan pericarp, MDA, O^2- were better the contrast. The active of the PPO,POD,SOD,CAT were also be restrained .The commodity value was enhanced after management.