Effects Of Different Post-ripening Methods On The Volatile Components And Related Gene Expression Characteristics Of ’Brazil Banana’

Banana is one of the four major traded fruits in the world fruit market,and banana aroma,as one of the important indicators that constitute the characteristic flavor quality evaluation of bananas,greatly affects the flavor quality of bananas and processed products.At the same time,it is also an important factor in enhancing the core competitiveness of the market and consumers’ desire to purchase.Therefore,in-depth understanding and analysis of the volatile compounds and aroma characteristics of the main domestic banana species ’Brazilian banana’,and in-depth study of the formation mechanism of fruit volatile components,in order to solve the problem of domestic banana quality and variety improvement Provide scientific and basic research data for solving problems.The purpose of this study is to determine the volatile components,basic physical and chemical indicators of maturation of the ’Brazil banana’ fruit that have undergone different ripening treatments and preservation treatments,mining the overall aroma composition of the ’Brazil banana’ fruit and its correlation with the synthesis pathway of volatile substances in the banana fruit Analyze the expression characteristics of genes in different post-ripening methods and different stages of maturity,clarify the expression characteristics of aroma synthesis genes and fruit volatile substances,and provide a basis for banana quality improvement,quality optimization,storage and preservation,transportation and circulation,storage and processing,etc.The research data provide a reference for banana fruit flavor quality evaluation and by-product processing.The main findings are as follows:(1)There are obvious differences in the ripening cycle of fruits among the four treatment groups.ETH and Me JA significantly accelerated the ripening progress of fruits,which made the appearance quality of fruits superior to that of the control group.The 1-MCP group had the longest ripening cycle and the worst appearance quality.ETH and Me JA increased the color value(L*,a* and b*)and decreased the color value h*,among which the color value of ETH treatment group was the highest,followed by Me JA group and 1-MCP group.ETH and Me JA made the peak time of respiration peak of ethylene release significantly earlier,and the corresponding fruit hardness also decreased rapidly.On the contrary,1-MCP significantly inhibited the changes of the above indexes.Finally,based on the analysis results of fruit phenotype,color,hardness and ethylene release,three banana samples with close maturity(defined as color-changing period,yellow-maturing period and over-maturing period)were selected from four treatments for analysis.It was found that the content of fruit in ETH group was the highest in TSS color-changing period,followed by Me JA group;The TSS content of fruits in Me JA group was the highest in yellow ripening stage,followed by fruits in ETH group.The content of TSS was the highest in ETH fruit,followed by Me JA and the control group.Comprehensive analysis showed that the appearance quality and soluble sugar content of fruits treated with Me JA and ETH,while fruits treated with 1-MCP could prolong the shelf life of fruits,but the quality of fruits declined.(2)There were 75,81,70 and 45 kinds of volatile substances in the control group,ETH,Me JA and 1-MCP treatments respectively.Compared with the control group,it was found that ETH treatment increased the types of volatile substances and the relative content of total ester volatile substances in yellow and over-mature stage,and decreased the content of total aldehyde volatile substances in color changing stage,yellow and over-mature stage.Me JA reduced the types of volatile substances in fruits at three mature stages,but increased the content of total ester volatile substances in yellow and over-mature stages,and decreased the content of total aldehyde volatile substances in color-changing,yellow and over-mature stages.1-MCP not only reduced the types of volatile substances in fruits in three post-ripening stages,but also reduced the relative content of total ester volatile substances in each stage.The total ester content was very low in color-changing stage and yellow-ripening stage,even undetected.On the contrary,the relative content of total aldehyde volatile substances increased significantly in the color-changing stage and yellow-ripening stage.On the whole,ETH and Me JA have similar effects on the fruits of’ Brazil banana’,shortening the postripening period and improving the flavor quality of fruits,while 1-MCP prolongs the storage time and reduces the flavor quality of fruits.(3)The aroma analysis of’ Brazil banana’ showed that ETH and the control group covered 14 aroma types in the color-changing period,and the highest aroma ratio was Qing Xiang and fat aroma.The aroma types of ETH in the yellow ripening period were less than those of the control group,with the highest proportion of fruit aroma and the highest weight of Qing Xiang of ETH.There are more kinds of ETH aroma in over-mature stage than the control,and the proportion of cheese aroma is second only to fruit aroma,while the proportion of Qing Xiang in the control group is still relatively high,second only to fruit aroma.The aroma types of fruits in Me JA treatment group were less than those in control group in three periods,and the proportion of each aroma was also significantly different.1-MCP treatment contained 14,10 and 12 kinds of aroma types in color-changing,yellow-ripening and over-ripening stages,respectively,and the aroma types in yellow-ripening and over-ripening stages were less than those in the control group.Although there are some differences among the aroma types in the three mature stages of the four treatments,the main contribution aroma types in each mature stage are basically unchanged.(4)ETH increases the expression level of HPL and BCAT member genes,and plays an important role in promoting expression of most genes of LOX,PDC,ADH and AAT.The effect of Me JA on fruit aroma synthesis-related genes is similar to that of ETH.It promotes the expression of the member genes of HPL and BCA.It promotes PDC and LOX genes and inhibits the expression level of some genes.It has an effect on the ADH gene.The overall expression level of the gene is reduced,and the effect on the PDC gene is not obvious overall.In addition to the insignificant effect of 1-MCP on the ADH gene,the HPL,LOX,PDC,BCAT and AAT genes exhibited varying degrees of inhibitory effect on the expression of HPL,LOX,PDC,and AAT genes in the three mature stages.