Effects Of Bagging On Aroma Compounds And Its Physiological Mechanism In ’Kuerlexiangli’ Fruit

In this study, we compare the effects of purple plastic film bag and single-layer white paper bag (Kobayashi NK-15) on aroma compounds, fatty acids, amino acids, soluble sugars and related enzymes’s activities in’Kuerlexiangli’(Pyrus sinkiangensis Yii) fruit combined with non-bagged fruit as control. The main results were as follows:1. The total amounts of aroma compounds in ’Kuerlexiangli’ increased with the development of the fruit, but it fell when the fruit riped. In the earlier period of fruit development, the proportion of alcohols and aldehydes is very low, with the growth and development of the fruit, the content of alcohols and aldehydes’ increased, while the content of esters and hydrocarbons decreased. But when the fruit was ripe, the content of alcohols and aldehydes increased, the content of esters and hydrocarbons reduced, there were significant differences in aroma compounds’ composition and content between different treatments. The contents of aroma compounds in fruit with bag were significantly lower than that of non-bagged fruit (P<0.05), but there were no significant differences between fruit with single-layer white paper bag and fruit with purple plastic film bag. Compared with non-bagged fruit,2 kinds of volatile compounds in the fruit with purple plastic film bag could not be detected and another 5 kinds of volatile compounds in the fruit with single-layer white paper bag were detected.2. There were five kinds of fatty acids were identified during the growth and development of pear:palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid; The content of the total fatty acids was the highest at 60 days after full bloom, it decreased with the growth of the fruit, slightly elevated at 145 days after full bloom, the content of total fatty acids decreased when the fruit was ripe; During the whole development of pear fruit, palmitic acid, stearic acid and oleic acid were low, linoleic acid and linolenic acid were high. Different treatments of palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid changed consistent trend levels, showed increased first and then decreased, then increased, then decreased. There were no significant differences in fatty acids between treatments.3. During the development of pear fruit, a total of 15 amino acids were detected, including aspartic acid, glutamic acid, glycine, alanine, cysteine, valine, methionine, leucine, isoleucine acid, phenylalanine, tyrosine, lysine, histidine, arginine and proline. In different treatmented fruits, the contents of aspartic acid, glutamic acid, valine, isoleucine, and alanin were high, so they were the main amino acids in pear fruit. The content of aspartic acid was the highest, glutamic acid and valine were higher. In the fruit ripening process, the content of total amino acids from different treatments was decreased, the content of amino acid in fruits with purple plastic film bag was significantly higher than that of non-bagged fruit,21.10% higher than the control, while the content of amino acid in fruits with single-layer white paper bag was significantly lower than that of non-bagged fruit. Effects of bagging on the different types of amino acids are also different, For the key amino acids, The content of aspartic acid, valine, alanine and isoleucine of fruit with purple plastic film bag increased, while reduced in the fruit with single-layer white paper bag. But the content of glutamic acid reduced both in the fruit with purple plastic film bag and in the fruit with single-layer white paper bag.4. Soluble sugars of pear fruit is composed of sucrose, glucose, fructose and sorbitol, the content of fructose was the highest during the development of the whole growth from different treatments, followed by sorbitol, glucose, sucrose’s content was the least. Throughout the growth and development process, sucrose, glucose and fructose showed an upward trend overall, sorbitol showed downward trend after the first rise, the total soluble sugar content showed an upward trend overall. Different treatments of the total sugar content were slightly different in the various periods, The contents of the soluble sugar in fruit with bag were sifnificantly lowwer than that of non-bagged fruit (p<0.05), but there were no siginificant differences between fruit with single-layer white paper bag and fruit with purple plastic film bag.5. The activities of the LOX and PDC increased with the fruit growth, while the activities of ADH and AAT fluctuations, but the activity was elevated when the fruit was riped, the activity of HPL generally increased, but later changes relatively stable; bagging has different effects on different related enzyme’s activity, the effects of different types of bags was also different. Sets of purple plastic film bags increasesd the activity of LOX and AAT, sets of single-layer white paper bags elevated ADH’s activity. Purple plastic film bags and single-layer white paper bags have reduced the HPL’s activity.