Study On Fresh Keeping Techniques Of Seedless Litchi Chinensis

Seedless litchi chinensis is one of tropical fruit resources specific in China, mainly originating from Hainan Island, there is no record of this speicis in overseas so far, ever since it was discoveried in the Hainan Qiongshan of Hainan in 1995, several grafts methods have been used for propagation during the the passed 6 years till 2000, however were still under 1%, which resulted in failure of commercialization and cultivation, In 2001, the seedless litchi was identified as a mutant by DNA relationship analysis method and anatomy technology. Uncompatibility of scion with stock is the main reason of extremely low level of survival rate. To solve this difficult problem, the study group start to develop 22 litchi specific SSR (simple sequence repeat)markers in independence by the application of modern molecular biological method since 2001. These locus-specific SSR markers were used to analyze the genetic diversity within 37 litchi germplasm materials. The result showed that the similarity between one of 37 litchi germplasm materials and the seedless litchi of Hainan Lu Qiao was biggest. The similarity mitrix achieves to 0.76.The survival rate of grafting rises to 85% above, it is named by Qin He 1 . It blossomed and had fruits for the first time in 2005. The fruits have good shape. The luster of fruits is bright. The flavor of fruits is excellent. It has been attractive in the domestic and foreign markets. The study is one part of the main contents of China National 863 guidances program .The main research content includes: The biological antioxidant, the complex experiment of biological antioxidant and biology membrane for fresh-keeping, the new type of biology membrane for fresh-keeping, type of bag test for fresh-keeping, optimum temprature and humidity test in process of fresh-keeping, PH value changes of pericarp in process of fresh-keeping. influence, simulation the long-distance transport experiment, and the test of previous treatment with ice-water and temperature water in fresh-keeping process. All these test carried out as follows:(1) suppression hormones which cause senescence producing before and after harvest of seedless litchi.(2) To keep the active of anthocyanin for the purpose of fresh-color maintenace by suppresses the activities of enzyme, such as PPO, POD, to minermize the replacement of the hydroxyl (-OH) on glucoside by phenolate.(3) To adjust persontage of jasmine acid, to suppress the senescence of fruit.(4) New antioxidant which can provide extra hydroxyl was used to protect the oxidation of anthocyanin caused by the enzyme, no antibiotics was used in the whole experiment.(5) To maintains optimum temprature and humidity to keep the fruit at the lowest physiological activity condition and to prevent the fruit browning and mildewing.Main results showed as follows:1. The biological antioxidant Number 1 used for fresh keeping At the temperature 2℃, with the condition of being sealed in PE fresh keeping bag, results showed that the fruit browned slightly which indicated that anthociny was maintened slightly, while the fruit of contronl showed medium browning. However 50% of fruit both from treatment with biological antioxidant number 1 and control showed mildewing. Indicated that biological antioxidant number 1 did not work against mildew.2. The biological antioxidant Number 2 used for fresh keeping The biological antioxidant Number 2 was sprayed onto the litch fruits one day before harvest with pH value of 4.0. fruit were harvested one day after spray, and stored at the temperature 2℃, with the condition of being sealed in PE fresh keeping bag, 36 days later the fruit still kept fresh-red without any mildewing, and the flavor of the fruit was still fresh, while the fruit of contronl turned into brown with mildewing percentage of 100%. The results showed that The biological antioxidant Number 2 played an important role both in the protecetion of anthociny and in antimildew as well.3. The biological antioxidant Number 3 used for fresh keepingThe biological antioxidant Number 3 which was obtained from natural resources was sprayed onto the litch fruits one day before harvest with pH value of 4.0. fruit were harvested one day after spray, and stored at the temperature 2℃, with the condition of being sealed in PE fresh keeping bag, 36 days later the fruit still kept fresh-red without any mildewing, the flavor of the fruit was still fresh, and the pericarp still kept fresh shining color, while the fruit of contronl turned into brown with mildewing percentage of 100%. The results showed that The biological antioxidant Number 2 played an important role both in the protecetion of anthociny and in antimildew as well.4. The biological antioxidant Number 2 plus the new type of new bioloical sourced membrane for fresh-keeping 34 days later the fruit browned slightly without any mildewing, and the flavor of the fruit was still fresh, the fruit was shining with the coat of new bioloical sourced membrane. while the fruit of contronl turned into brown with mildewing percentage of 100%. Both for the treatment and control, the fruits were rotten when they were checked at 69 days after treatment.5. The biological antioxidant Number 2 plus pericarp pH value adjusting for fresh-keeping Both the treatment and control were stored at the temperature 2℃, with the condition of being sealed in PE fresh keeping bag, 32 days later the fruit of treatment which adjusted pH value to 4 showed the best condition,browning slightly with slightly mildewing, while the fruit of control browned heavily. However the treatment with adjusting pH value to 9 showed severely browning. It indicated that the litch should be kept in slight acid condition with the anthociny could be kept at slight acid condition.6. The new bioloical sourced membrane was used for litch fresh keeping Laccaic was used as bioloical sourced membrane, Both the treatment and control were inspected after 32 days, the fruit of treatment browned slightly without mildewing, the fruit was shining with the coat of new bioloical sourced membrane, browning partially on the surface, white stripped. while the fruit of control browned heavily. It indicated that the laccaic might play an important role in antimedew,and in suppression respiration of fruit.7. New type of bag for fresh keeping uesd in this study the result showed that the fruit both from treatment and control were well kept when check at before 21days, and the fruit kept in PE bags released free water,however there was no free water in the new type of bag.8. optimum temprature and humidity The results showed that the optimum temprature and humidity for fresh keeping of seedlitch were low temprature and high humudity.9. The fresh keeping during the long-isitance transportation and saling process.(1) seedless litch were packed derectly after harvest in foam container with 16 bags and 4 ice bags each, 1kg fruits per bag, and were shipped to Beijing by air, totally 200kg 1itchi were shipped, and 10 hours in total were costed including from packing, waiting, tranporting and arrival at Beijing. Till sold out, all the fruits kept fresh red in colour without any changes in colour. However the disadvantage of this method is few fruits were mechanical injury caused by the ice bags pressure.(2) because the seedless litchi is very popular in Beijing, The second lot were send to Beijing in the next day at room temprature, packing in sealed PE bags without ice bags. Totally time costed for transportation is 8 hours, and time costed during the saling process is about 1-8 hours. Accooring tot our trial, fater harvest, the fuirt can be kept at room temprature for one day then can be stored at 2—5℃for at least 2 weeks, all the fruits kept fresh red in colour without any changes in colour.10. The result of the previous treatment with ice-water for seedless litchi showed that it is not necessary to keep fresh for them in this way.11. The result of the previous treatment with hot-water for seedless litchi showed that it has some good to keep fresh the fruit without mildewing.The colour of fruit turnt from red to yellow after being soaked in 47℃water for 15mins and being dried on the air. It confirmed that the partial anthocyanin was destroyed. The fruit was browned without mildewing in a week when kept fresh in 2℃with PE bags.