Effect Of CPPU Treatment On Postharvest Quality Of Lotus Seeds And Chlorophyll Metabolism Of Lotus Peel

Lotus is one of the high quality resources of our country,and it is of great nutritional and medicinal value.Fresh lotus seeds have abundant nutritive val and delicious taste,so it’s very popular with consumers.The harvesting of the lotus seeds was concentrated in July and September,and the respiration rate was still intense after harvest.The quality of the lotus seeds which is not treated by treatment is often decreased after 4⁵ h,so that the sales period of fresh lotus seeds is limited,which can not meet the demand of consumers.At present,there is little research on the preservation of fresh lotus plants,which can not fully meet the needs of the development of lotus industry.On the basis of previous studies,the experiment was carried out with the treatment of fresh lotus by CPPU.The effect of CPPU on the preservation of lotus was studied from postharvest quality of lotus pods,cell wall polysaccharides of lotus seeds and chlorophyll metabolism of lotus peel.The main research contents and results were as follows:The harvested lotus pods were treated with different concentrations（2.5,5,10,15,20mg/L）of CPPU.The results showed that the optimal concentration was 5 mg/L.The further study found that CPPU treatment inhibited the browning degree.At the 8th day,the CPPU contents of CK0 and CK1 were 3.1 and 2.9 times respectively of the CPPU treatment,while the CPPU treatment remained at a low level throughout the storage time.In addition,CPPU treatment also maintained a good phenotype of lotus and lotus seeds,and inhibited the TSS accumulating,starch losing and respiration rate of lotus pods.Moreover,the CPPU treatment retarded the increases of MDA and H₂O₂ contents,as well as the rate of O₂^·-generation in fresh lotus seeds.At same time,the activities of SOD and CAT were significantly improved,and the activities of POD and PPO were inhibited by CPPU treatment.In addition,the result indicated that the maximum CPPU residue was 0.0058 mg/kg,which is far less than the Chinese standard.The study found that 5 mg/L CPPU can inhibit the degradation of polysaccharide in the cell wall of the lotus plant,and can effectively maintain the good phenotype of the lotus and lotus seeds,and maintain the delicate and tender taste of the lotus seeds.In 4⁸ d,the sensory score in the same storage period is 20 points higher than CK.At the same time,the infrared analysis of the cell wall of the lotus seed showed that the treated lotus seeds maintained a good cell wall polysaccharide carbon chain structure(1100¹060 cm^-1).On this basis,further studies showed that CPPU treatment inhibited the activities of pectin-degrading enzymes such as pectinesterase（PE）and polygalacturonase（PG）,and the activities of cellulose-degrading enzymes such as cellobiohydrolase 1（C1）,β-1,4-endoglucanase（Cx）andβ-glucosidase.Thus,covalent-soluble pectin of the seeds was inhibited by CPPU treatment,resulting in less accumulation of water-soluble pectin and ionic-soluble pectin,and lotus seeds in treated sample possessed higher contents of cellulose and hemicellulose.The content of covalent-soluble pectin treated by CPPU was significantly lower than that in CK,and the content of pectin was decreased,for example,in the 4th day,compared with the 2th day,CK and CPPU were respectively 25.83%and 2.68%respectively.At the same time,the results of the cell wall ultrastructure showed that CPPU treatment maintained the structure of the cell wall and the morphology of cellulose microfibril of the lotus seed.What’s more,the separation rate of the cell wall plasmolysis was retarded by CPPU treatment.It was found that 5 mg/L CPPU had a certain effect on chlorophyll degradation metabolism in lotus,and chlorophyll metabolism process of lotus peel was participated by three enzymes of chlase,MDcase and PPH.And chlorophyll metabolic products include:pheophytin a,chlorophyllide a,chlorophyllide b,and pheophorbide a.CPPU treatment can inhibit the activity of chlase,MDcase and PPH,delay the degradation of chlorophyll,and maintain chloroplast integrity.A nonfluoreseent chlorophyll catabolites NDCC was identified.