Study The Drying Methods On The Effect Of Phenolic Substances And Its Quality Of Lemon

Lemon has good nutrition and medicinal value,but its taste very acid.Generally,we do not eat lemon directly,but processed into dried food or drink.China,India and Argentina are lemon major producers.Lemon in China is divided into yellow lemon and lime according to the skin colour in China.Lemon is rich in phenolic substances,such as orange peel glucoside,saint grass cedrat glycosides,ritin,nagrigin,vanillic acid,protocatechuic acid and so on.It has a great significance and economic value in food industry development and utilization,because of its antioxidant,anticancer,antibacterial performance and prevention of cardiovascular disease,and so on.Spectrophotometer method and Ultra High Performance Liquid Chromatography(HPLC)method were adopted to separate and quantify the phenolics,total phenolic content and antioxidant activity in four species lemon.The research includes lemon varieties contrast,lemon slices drying analysis and so on.The main research content can be divided into three parts as follows:(1)Distribution of phenolics of four lemon and their antioxidant activityThe results showed that the contents of total phenol and antioxidant activities in four kinds of lemon peel were significantly higher than those in pulp(p<0.05),and the total phenolics and antioxidant activity of Eureka Lemon peel and pulp were significantly higher than other three cultivars(p<0.05),and the total phenolics and ABTS~+free radical scavenging capacity of the‘xiangshui’lemon peel and pulp were the lowest.There were significant differences in phenolic acids and flavonoids among different lemons,Among the4 lemons,21 phenolic compounds were detected,including 6 phenolic acids,6 flavonoids,6flavanones,3 polyoxymethyl flavonoids.The main phenolic compounds in lemon were flavanones,accounting for 61.82~91.61%of total flavonoids,and the total content of phenolic acids in the green lemon peel was the highest(535.62 mg/100g DW),the content of flavonoids in the Eureka peel was the highest(1506.33 mg/100g DW).The regular of the content in the pulp was similar to the peel,but the pulp was significantly lower than the peel(p<0.05).There were 15 phenolic compounds in Eureka peel and pulp,the highest content was eriocitrin,and the neochlorogenic acid was the highest content of phenolic acid.Small lime,green lemon and‘xiangshui’lemon peel and pulp were detected in 19,16,15kinds of phenolic compounds,and the content of hesperidin was the highest among these varieties,and vanillic acid was the highest content of phenolic acid.The content of total phenolics and total flavonoids in different varieties of lemon had a highly significant positive correlation with ABTS~+,and the total phenolic content had a significant positive correlation with DPPH.(2)Impact of dehydration methods on the phenolic compounds and antioxidant activity of lemon slicesThe results showed that The content,ABTS~+,FRAP of free total phenolic in four dried lemon slices was higher than these of bound total phenolic,respectively,while the scavenging DPPH capacity of bound total phenolic in all four dried lemon slice was higher than that of free total phenolic.The main phenolic compounds in the four kinds of dried lemons were flavonoids,and their flavonoids were significantly higher than phenolic acids.The free phenolics in the lemon were mainly hesperidin,hollycine and rutin.The total amount of phenolics was 91.18%~94.92%.The phenolics were mainly protocatechuic acid,naringin and hesperidin,and the content of the three phenolics was 81.83%~83.64%of the total bound phenolics.At the same time,the contents of total phenols and total flavonoids in lemon were respective significantly correlated with ABTS~+and FRAP heat treatment has different effects on phenolic compounds in lemon.Compared with FD treatment,heat treatment resulted in the decrease of total phenols,total phenolic acids and bound polyphenols in lemon,the total amount of free phenolic acid,the content of bioaccessible phenolics and its bioavailability increased;The total amount of flavonoids increased,while the total amount of free flavonoids decreased.Among the AD,IRD,and VD treatments,it was found that AD treated samples contained the highest content of total phenolics(325.77mg/100g DW)and total flavonoids(325.77 mg/100g DW),as well as the highest bioaccessibility of phenolics(42.92%).Thus,AD could be a promising dehydration method for drying of lemon slices in an industrial scale.The content of total phenolics and total flavonoids in free and Free of lemon had a highly significant positive correlation with ABTS~+and FRAP.(3)Study the different drying methods on the effect of quality of lemonThe results showed that freeze-dried Lemon Piece present light yellow,to keep type and content of volatile substances effect is good effect,was the ideal way of drying lemon;Other of the lemon slices Browning.The physical-chemical properties of the lemon slices were significantly different.The contents of total lemon,β-carotene and Vc in the lemon slices were significantly higher under vacuum conditions.the order of reducing sugar content was hot air drying<FD<IRD<VD.The limonin contents of dried Lemon Piece prepared by IRD was lowest,the nomolin contents of dried Lemon Piece prepared by FD was lowest,and the contents of both were highest by VD.22 kinds of volatile substances were identified from lemon slices by Gas Chromatography-Mass Spectrometry,and occupied more than 90%of the total peak area.Terpene were the main volatile substances,and the content of D-limonene were more than 67%which was the main volatile substances of lemon slices.Besides the FD,the VD has the advantage of retaining volatile matters of lemon slices.As for AD,the types and content of volatile substances content were loss most.Considering the cost of FD,VD was the best way to keep the taste and nutrients of the lemon.To effectively reduce the lemon browning degree and retain the higher polyphenol content,the temperature of AD was recommended 60℃.