Effect Of Hydrogen Treatment On Postharvest Quality And Preservation Of Kiwifruit

Kiwifruit is small caloric and has high amounts of vitamin C.It is a kind of delicious fruit with abundant nutrition and medical value.However,kiwifruit belongs to berry and climacteric fruit,and the characteristics of skin thin,juicy flesh and vigorous postharvest respiration lead to quality deterioration and short storage life easily at room temperature.In order to extend the storage life of kiwifruit,in this paper,we had done some experiments on ’xu xiang’ kiwifruit,then kiwifruit was treated with different concentrations of hydrogen(H2),and the pick out the most appropriate H2 concentration.Based on this,we further study the effect of H2 treatment on changes of nutrient substance and preservation mechanism of kiwifruit during post-harvest storage at(19±1)℃.The main results are as follows:1 Picking out the most appropriate H2 concentrationThe kiwifruit was treated with different concentrations of H2(4.5 μL/L,45 μL/L and 450μL/L),different treatment methods(H2,1-MCP and C2H4)and different concentrations of H2 secondary treatment(1.5 μL/L,3 μL/L,4.5 μL/L and 6 μL/L),and then storage at(19±1)℃.From the view of firmness,soluble solids content(SSC)and malondialdehyde(MDA)content were evaluated.Our results revealed that H2 displayed different effects in inhibiting the quality of kiwifruit.The results showed that the firmness of kiwifruit treated with 4.5 μL/L,45 μL/L and 450 μL/L H2 were higher than that of CK by 20.56%,1.01%and 6.60%respectively,and MDA content was 87.59%,94.09%and 88.44%in the CK,respectively.In addition to,the higher the concentration of C2H4 could stimulate the firmness decreased faster of kiwifruit.However,4.5μl/L H2,0.5 μl/L 1-MCP and 4.5 μl/L H2 secondary treatment were 1.39,1.84 and 1.70 times of CK,respectively.Notably,4.5 μL/L of H2 secondary treatment showed more effective than higher concentration of H2.Furthermore,the firmness of the secondary treatments of 1.5 μl/L,3μl/L,4.5 μl/L and 6 μl/L H2 were 0.45,0.57,1.25 and 1.18 times of CK,respectively.And soluble solids content were 104.46%,101.47%,90.90%and 94.79%in the CK,respectively.It can be seen that lower concentration of H2 treatment can reduce the firmness sharply of kiwifruit and the formation of MDA much better,but H2 concentration would promote fruit softening aging when it is too low.Direct H2 fumigation treatment showed that H2 molecules were involved in the regulation of kiwifruit ripening and senescence.Therefore,it indicated that H2 was beneficial for delaying fruit ripening.Nevertheless,the H2 concentration should be controlled with in a certain of leve,the concentration is too high or too low will have a negative impact on the fruit.Based on the above results,we used the 4.5 μl/L H2 secondary treatment to pretreat kiwifruit.2 Effect of H2 treatment on postharvest nutritional quality and antioxidant capacity of kiwifruitThe results show that application of the 4.5 μL/L H2 was sufficient to delay kiwifruit softening and decrease the titratable acid content,and inhibit soluble solid content formation of kiwifruit.Simultaneously,H2 can maintain the fruit chlorophyll,carotenoids,total phenolics,flavonoids and anthocyanins content.Storage to the 12 day,the chlorophyll content decreased by 43.10%in the CK and 21.20%in the H2 treatment,while that of H2 group was 1.20 times of CK.CK and H2 groups total phenol content decreased by 23.80%and 6.50%,respectively.The contents of flavonoids and anthocyanins in H2 group were 8.00%and 27.78%higher than that in CK,respectively.Additionally,H2 can maintain the ascorbic acid and oxidized glutathione content in the kiwifruit at a high level,improve the kiwifruit to scavenge DPPH,·OH,O2·-and enhance the ability to chelate iron ions.The total AsA content of H2 group was 1.11 times of the CK.At the same time,AsA content in CK group decreased by 10.00%,while AsA content kiwifruit in H2 group increased by 1.09 times.The DHA content of kiwifruit in H2 group was maintained at a high level,and DHA content was 27.21%higher than CK.Besides,the total GSH,GSH and GSSH contents in H2 group were 1.03,1.12 and 1.28 times of CK,respectively.Moreover,H2 treatment could significantly enhance the antioxidant capacity of kiwifruit.At the 12 day,the DPPH,·OH,O2-and iron reducing power of H2 group were 1.20,1.03,1.07 and 1.03 times of CK,respectively-So as to improve the antioxidant capacity during kiwifruit storage,eliminate fruit oxidation damage,enhance fruit storability,therefore maintaining the nutritional quality and commodity value of kiwifruit.These results clearly revealed that H2 could increase the radical-scavenging activity and maintain the nutritional quality and commodity value of kiwifruit during storage.3 Effect of H2 treatment on sugar content and metabolism related enzymes of kiwifruitWe researched the effects of 4.5 μL/L H2 secondary treatment on the sugar contents of and metabolism related enzymes of kiwifruit.Our study results demonstrated that the firmness and the starch were continuously degraded of kiwifruit in the prolongation of storage time.At thesame time,the contents of soluble solids,reducing sugar and soluble sugar were increased rapidly,and the contents of glucose and fructose were accumulated.At the end of storage(the 12 day),the contents of reducing sugar,soluble sugar,glucose,fructose and sorbitol in the CK group were 13.81%,80.21%,8.37%,14,44%and 19.03%higher than those in H2 group.Meanwhile starch and sucrose content of H2 treatment were 15.18,1.26 times of the CK,respectively.Compared with CK,the activities of sucrose synthase and sucrose phosphate synthase were increased by 51.98%and 15.86%,respectively.However,the activity of sucrose decomposing enzyme,neutral invertase and acid invertase in the CK were 1.27,1.62 and 3.56 times of H2 group,respectively.It is hypothesized that H2 was involved in the regulation of sucrose metabolic activity of kiwifruit fruit,which could improve the activity of sucrose synthase and sucrose phosphate synthase and promote the formation of sucrose.In addition,H2 could reduce sucrose-degrading enzyme,neutral invertase and acid invertase activity of kiwifruit,thereby reducing the decomposition of sucrose.Therefore,the addictive H2 treatment would retard the accumulation of reducing sugar,soluble total sugar,glucose,fructose and sorbitol,meanwhile the effect of reducing the degradation of starch and sucrose were more prominent especially in the late storage.4 Seeking optimum method of RNA extraction conditions in ’xu xiang’ kiwifruit by CTAB method.Effect of H2 treatment on ethylene production and its related gene expression in kiwifruitIt is one of the important factors to carry out the downstream experiment to extract the high quality RNA of’xu xiang’ kiwifruit by optimizing the CTAB method.The key to the optimization of CTAB is to increase the proportion of CTAB,β-mercaptoethanol and LiCl to 2.50%,10.00%and 50.00%.Moreover the amount of chloroform/isoamyl alcohol extraction and 70%ethanol washing times were increased to 3 times.Meanwhile,adding spermidine to 0.5 g/L can effectively inhibit RNase activity.In this paper,to extracte the total RNA of kiwifruit served as the reverse transcription template through the CTAB method,which can remove the protein,polysaccharide and polyphenol thoroughly and increase the purity,integrity and yield of RNA in kiwifruit.The genes of ethylene synthesis and ethylene receptor genes have different expression patterns in different stages of kiwifruit ripening.Ethylene was not detected until the end of the experimental period(9 day)of kiwifruit in H2 group,and it is 24.40%of CK.At the 9th day,4.5μL/L H2 was an effective concentration to inhibit the expression of AdACO1、AdACO2、AdACO3、AdACO4、AdACO5 and AdAC06,and they were 70.90%,27.70%,8.10%,11.40%,87.70%and 75.10%of CK group.Meanwhile,H2 treatment could significantly inhibit the expression of ACS gene,especially AdACS3,in the medium(3-6 day)of storage.In addition,H2 treatment could enhance AdERS1a,AdERS1b and AdETR1 expression levels at pre-storage(0-6 day).On the 6th day,the expression levels of AdERSla,AdERSlb and AdETRl in CK group were about 54.80%,49.10%and 86.10%compared with H2 group.The expression of AdERS1a,AdERS1b and AdETR1 were significantly inhibited by H2 in the later stage of storage(9 day),and the expression of AdERS1a,AdERS1a and AdETR1 in CK group was about 1.10,1.90 and 2.90 times of H2 treatment.This indicated that there is a complex relationship between ethylene synthesis related genes and ethylene receptors,and H2 treatment can significantly affect the expression of ethylene synthesis related genes and ethylene receptor genes,especially in the late storage period.Furthermore,H2 treated suppressing the sensitivity of fruit to ethylene,and thus delay ripening and senescence of kiwifruit.In general,the results show that application of the 4.5 μl/L H2 secondary treatment was the optimal concentration and was sufficient to delay kiwifruit softening.Based on the optimal concentration,H2 could increase the radical-scavenging activity and maintain the nutritional quality and commodity value of kiwifruit during storage.Besides,the 4.5 μl/L H2 secondary treatment could significant monitor the content of sugur and metabolism related enzymes in kiwifruit.More importantly,H2 treatmnt could suppress the sensitivity of fruit to ethylene and significantly affect the expression of ethylene synthesis related genes,and thus delay ripening and senescence of kiwifruit.