Effect Of The Combination Technique Of Heat Shock And Chemical On The Storability Of Ponkan Fruit

China is the biggiest country in the production of oranges. Now chemical is still a major technique to keep the fruits fresh. It can restrict the germs on the surface of the Ponkan peel to keep the Ponkan fruit fresh. However, with the increase in the attention to the health and safety and the overuse of the chemical, it is urgent to find some safe substitute which is free of toxin and low in chemical residue as well as effective to replace the chemical being used now. Heat treatment is a simple way to control the pest and the disease, prolong the aging, and improve the quality of the fruit. There are many researches related to the heat treatment but a few about the combination of the heat treatment and the chemical. In this thesis, Ponkan fruit is used to study the effects of the combination of the heat treatments and the chemical on the decay rate, quality changes after harvest. The main results are as follows:1.The combination of the heat treatment(55℃,20s) and 25% chemical can effectively reduce the decay rate of the Ponkan fruit during the storage and the shelf life. So this treatment can be applied in the production of the Ponkan fruit.2.The effect of the combination of the heat treatment and the chemical on color, sugar and acid of the Ponkan fruit during storage are studied. It is found out that there is no significant difference in the change of color. There is a downward trend in the content of sucrose, decreasing from 53.89 mg/g to 29.11 mg/g, while an upward trend in the content of glucose and fructose, with glucose seeing a rise from 3.37 mg/g to 5.49 mg/g and fructose from 10.71 mg/g to 16.31 mg/g. Citric acid is the most important and abundant organic acid in the Ponkan fruit, and during the storage, the fruits see a sharp decrease from 10.08 mg/g to 1.30 mg/g.3. Researches have been done in terms of bioactivity and antioxidant activity. The content of total phenolics in peel is higher than that in the pulp, and content of total phenolics in peel sees a slight increase, peaking at 1.28 mg CAE/g FW. There is an steady rise during the middle of the storage while the minimum amount of the total phenolics is only 0.71 mg CAE/g FW. The content of flavonoids remains steady in the peel, ranging from 0.55 to 0.89 mg catechin/g FW. Antioxidant activity has no significant difference both in the peel and pulp in the Ponkan fruit. There is a slight fluctuation in the content of flavonoids in the peel but a similar level in the content of flavonoids in the pulp.4. Some researches have been done about the CFU and the 2,4-D chemical residue. During the last period of storage, the CFU reaches the peak, indicating that there are many germs and bacteria on the surface of the Ponkan peel. The CFU of the fruits with the heat treatment is less than that of the fruits without the heat treatment. CFU is 1053 in the Ponkan fruit with the combination of the heat treatment and 50% chemical while CFU is 1116 in the Ponkan fruit with 50% chemical treatment. CFU is 666 in the Ponkan fruit with the combination of the heat treatment and 100% chemical while CFU is 727 in the Ponkan fruit with 100% chemical treatment. There is more 2,4-D residue in the peel than in the pulp. The level of the 2,4-D residue is higher in the fruits with the heat treatment than in the fruits without the heat treatment. During the 150th day after treatment, the 2,4-D residue cannot be detected by the machine in the Ponkan fruit with the combination of the hot treatment and 25% chemical.5. The content of the ethanol、acetaldehyde、pectin and fiber are quantified in the research. The content of the ethanol sees an upward trend, peaking at 1.12μL/kg, which is 26 times the amount of ethanol in the first stage. The content of acetaldehyde remains steady, ranging from 0.09 to 0.16μL/kg. The content of the soluble peerin in the peel is more than that in the pulp. There is an upward trend in the content of the soluble pectin while there is a downward trend in the protopectin in the peel. The content of the soluble pectin and protopectin remains slightly rising in the pulp during the storage. The level of pectin remains steady in the peel and gradually increases in the pulp during the storage. There is no fluctuation in the fiber in the peel until the last period of.storage. The content of the fiber with the heat treatment is higher than that without the heat treatment on the 150th day, peaking at 4.17 mg/g.