Effects of different types of fruit bags on fruit quality in Tianshihong pomegranate

Abstract: 【Objective】Fruit bagging, as a physical protective measure, can effectively avoid mechanical damage during fruit growth and development, prevent from the attack by diseases and pests, reduce drug residues and fruit cracking rate, and maintain the fruit surface clean and tidy. In addition, fruit bagging changes the micro-environment such as temperature, light, moisture and air around the fruit to a certain extent, thus affecting the internal quality of the fruit, and is a key technical measure to improve the fruit quality. Tianshihong is a new super-soft-seed pomegranate bred by Zhengzhou Fruit Research Institute, CAAS. It has wide adaptability and bright red fruit surface and seeds at maturity, and is rich in anthocyanins with sweet and soft flavor and excellent quality. However, the fruit skin is thin, and the phenomenon of dry and cracked skin is easy to appear in the later stage of fruit growth, which affects the commercial value. Therefore, the effect of different fruit bag treatments on the quality of Tianshihong fruit was studied to select the appropriate type of fruit bag and provide technical reference for thepromotion and application to Tianshihong super-soft-seed pomegranate.【Methods】In June 2022, five years old grafted Tianshihong trees were used as experimental materials in Zhengzhou area, and six different types of fruit bags were used to bag fruits, including transparent bag, white bag, nonwoven bag, blue bag, green bag and gray bag. Fruits on different canopy layers in different directions were randomly selected from each tree for bagging, and 20 fruits were randomly selected from each treatment. Ten fruits were randomly selected from each treatment at the maturity stage in mid-to-late September 2022, and physiological indexes such as single fruit weight, hundred kernel weight, peel thickness, peel color difference (a, b, c values), soluble solid content, organic acid content and Vitamin C content were determined. The type of suitable fruit bags for Tianshihong pomegranate was selected by comparing various fruit indexes under different treatment conditions.【Results】White bag and grey bag could increase the single fruit weight and hundred-grain weight. The single fruit weight and hundred kernel weight with the gray bag increased by 20% and 25%, respectively, compared with CK. However, the peel thickness with the grey bag significantly increased by 30% compared with CK. There was no significant difference in peel thickness between the rest treatments and CK. Different types of fruit bags had no significant effect on soluble solid contents in the fruit. Except white bag and blue bag, the Vitamin C contents in other 4 treated fruits were higher than CK fruits. Among them, the Vitamin C content of fruits treated with transparent bag increased by 20% compared with CK, and the effect was the most significant. The content of malic acid in bagged fruits increased by 12% to 45% compared with CK, and the effect of grey bags was the most significant. The citric acid content of fruits treated with transparent bag, blue bag, green bag and gray bag increased by 5% to 13% compared with CK, and the effect of transparent bag was the most significant. In terms of coloring, the a value of fruits treated with gray bag was the lowest and the color was the brightest. The difference in fruit color values was the smallest between transparent bag and CK, which was significantly higher than the rest treatments. In addition, the freshkeeping effect of fruit bags at different periods after fruit ripening was compared, and it was found that the fresh-keeping performance of transparent bags was significantly better than other fruit bags.【Conclusion】By comparing the quality of fruits treated with different bags, it is found that transparent bags can effectively protect fruit from damage, improve the fruit appearance, and increase the commerciality of Tianshihong fruit. It could prolong the fruit hanging period on the tree and increase the Vitamin C content in the fruit, but there was no significant difference in other sensory qualities. The results showed that transparent bags can be used as the main fruit bag type in the high-quality production and cultivation of Tianshihong pomegranate.