Effect Of Different Light Quality On Aroma Components And Flavor Of ‘Shine Muscat' Grape

‘Shine Muscat'(Vitis labrusca × V.vinifera)is a diploid mid-late grape variety bred from a cross of Akitsu-21 × Hakunan in Japan,which has the advantages of beautiful appearance,crispy and hard meat,rich flavor,strong disease resistance,not easy to crack,and resistant to transportation.It is very popular among consumers,growers and sellers.Peel browning is common to observed during planting,especially at the late-maturity stage.In addition,as the sugar content of the fruit increases,the fruit rust aggravates.Bagging technology is often used for solving these problems in production,while due to the difference between the materials of the bag,the difference in fruit quality is significant,especially the fragrance,which significantly affects grape commerciality.In this study,‘Shine Muscat'was used as the research material,the effects of 5different light quality fruit bags(nonwoven white bag,nonwoven green bag,paper white bag,paper blue bag,paper green bag)on the composition and concentration of volatile aroma compounds in fruits during physiology maturity and full maturity stage were studied.Based on the results,two different light quality fruit bags(nonwoven white bag,paper green bag)were selected to study their effects on volatile aroma components and accumulation pattern.Besides,research on the linalool,geraniol and related key enzymes,linalool synthase(LIS)and geraniol synthase(GES),which affect the fragrance of‘Shine Muscat'was performed.The results of the study will provide a theoretical and technical basis for the selection of fruit bags and the determination of the appropriate harvest time for‘Shine Muscat'.The main results are as follows:1.Effect of different light quality on the aroma and ripening of fruit.A total of35 volatile aroma compounds were detected in this study,including 13 characteristic aroma substances,9 types of terpene compounds that contributed the most to the‘ Shine Muscat ' flavor.Comparison between 5 different light quality fruit bag treatment and before and after unpacking showed that the content of terpene aroma substances treated with nonwoven fruit bag was significantly higher than other types of fruit bags before unpacking the bags.After removal of the bags,there was no significant change of terpene aroma substances treated with the nonwoven white bags,and the white paper bags treated fruits and the blue paper bags treated fruits increased significantly,while the paper green bags treated fruits had the lowest content of terpenes.In addition,the aldehyde content of the fruits increased in all treatments after removal of the bags and fruits treated with nonwoven fabric bags had the highest aldehydes before and after bags removal.The contents of linalool and geraniol were related to the changes of it's enzyme activities before and after bag removal.Results showed that the ripeness of the fruits and the accumulation of aroma substances were different due to the difference between the light transmittance and breathability of the different fruit bags.Fruits treated with nonwoven white bags had a rounded appearance,uniform coloring,high hardness,and low titrable acid content.Additionally,the characteristic aroma substance of terpenes was rich in linalool,and the rose fragrance was rich smell.The paper green fruit bags treatment had the advantages of improving the appearance quality,but it prolonged the fruit ripening period and reduced the aroma.2.Effect of different light quality on the accumulation of volatile aroma compounds in fruits.In this study,the composition and content of volatile aroma substances in the grape of two different fruit bags treatments were determined during the development of the ‘ Shine Muscat '.During the fruit growth and development,the nonwoven white bags treatment was more conducive to the accumulation of aroma substances,and the types of aroma substances in each period were more than the paper green bags treatment.The two main characteristic aroma substances of linalool and geraniol contents in the nonwoven white bags treatment increased as the fruit matures,and the accumulation was slow in the early growth period,but the accumulation was rapid in the later growth period.However,activities of related enzymes showed a trend of increasing first and then decreasing.Meanwhile,the trends of single fruit weight,fruit hardness and fruit shape index were consistent as the development of the fruits.There was no significant difference in the content of titratable acid between the two groups when the fruits reached commercial harvest,but the content of soluble solids was higher in the non-woven white bag treatment.The above results showed that different light quality fruit bags had different effects on the ripening and aroma formation of‘Shine Muscat'.White fruit bags with good light permeability and breathability could not only make the fruit ripen normally,but also have a round appearance and rich fragrance,especially nonwoven bags.Although colored fruit bags,especially green paper fruit bags could improve the peel coloration,it reduced the sugar content of the fruit and inhibited the activities of linalool synthase(LIS)and geraniol synthase(GES)which reduced the accumulation of linalool and geraniol,resulting loss of the unique rose flavor quality of‘Shine Muscat'.