Effect Of UV-C And Citric Acid Treatment On Fresh-keeping Of Postharvest Banana

Banana,a kind of tropical fruit with sweet and delicious flesh,is rich in starch,trace elements,vitamins,and has the function of clearing heat and moistening intestines.Due to the suffering from mechanical damage and physiological diseases during long-distance transportation and storage,banana harvesting time,transportation conditions,and storage and preservation techniques are necessary to maintain color flavor and shelf-life extending.At present,many physical,chemical and biological preservation methods are used to preserve fresh fruits and vegetables.Physical preservation technology is simple and easy to operate,and the chemical preservation technology will cause a certain amount of chemical residues.Although the biological preservation technology is green and safe,it has certain requirements for storage conditions.At present,there is no conclusion on the best preservation technology for banana storage.It has shown that UV-C irradiation is widely used as a safe surface sterilization technology in the theoretical research of fruit and vegetable preservation.However,the information about the application of UV-C irradiation in banana preservation is limited.In addition,citric acid,naturally present in plants,also plays a role in fruit preservation.Due to the differences in the nature of different fruits,it is necessary to determine the best preservation method or combine various preservation techniques for achieving a better storage and preservation effect,thus providing theoretical guidance for practical applications.In this paper,bananas were used as experimental materials to study the effects of UV-C irradiation,citric acid soaking and their combined treatments on preservation during shelf-life.First,the hardness and weight loss rate were measured,and the color change of banana peel was observed by using irradiated banana fruit with different doses of UV-C.The results showed that UV-C radiation for 1 min(0.0396KJ/m~2)maximally inhibited weightlessness and maintained the pulp hardness and peel luster,compared to the control and other radiation doses.Secondly,banana fruits were soaked with a variety of concentrations of citric acid.Then,the hardness and weight loss rate were measured,and the change of color was observed.The results showed that the soaking with 2.0%citric acid reduced the weight loss rate and maintained the pulp hardness and color.Therefore,1 min(0.0396 KJ/m~2)UV-C irradiation,2.0%citric acid,and their combined treatment first UV-C irradiation before citrate soaking)were used to further investigate the physiological effects of different preservation methods on quality parameters during banana shelf-life.During the storage of banana,given that physiological changes occur first in the peel,we analyzed the changes of malondialdehyde content,cell permeability,polyphenol oxidase,browning index,and ethylene content of peels under different treatments,and observed the structure changes in peels via scanning electron microscopy.The results showed that UV-C irradiation,citric acid treatment,and composite treatment all significantly inhibited the increase of malondialdehyde,cell membrane permeability,polyphenol oxidase activity,browning index,and ethylene content,and UV-C irradiation displayed the best fresh-keeping,followed by the combined treatment,and finally the citric acid soaking.Moreover,the banana peel cells under UV-C irradiation exhibited better original morphological structure of the cells with roundness and plumpness than that in the cells treated with both UV-C irradiation and citric acid soaking.In order to detect the effects of the different preservation treatments on banana flesh,several parameters related to taste and economic value of bananas,including hardness,soluble solids,titratable acid,soluble protein,vitamin C,and polyphenols,were determined.The results showed that UV-C irradiation,citric acid soaking,and combined treatment all significantly inhibited the decrease in hardness,vitamin C,total phenol,and titratable acid contents,and reduced the increase in weightlessness,soluble solids,and soluble protein contents,and UV-C irradiation displayed the best fresh-keeping,followed by the combined treatment,and finally the citric acid soaking.In conclusion,the comprehensive comparison of various physiological and quality indexes of bananas and the structure changes of peels under different preservation methods indicate that UV-C irradiation displayed the best fresh-keeping,followed by the combined treatment,and finally the citric acid soaking.We proposed that UV-C irradiation can be used as a green,safe and effective preservation technology for post-harvest bananas.