Research On Enzymatic Browning And Regulating Technology Of Fresh-cut Lemon

The research of enzymatic browning conditions in lemon was investigated in this paper,meanwhile,the article exploited compoite film preservation solution which included chitosan,anti-browning agent and essential oil.The research results provided technical reference and theoretical basis for storage of fresh-cut lemon.(1)The single factor-response surface optimum was used to determine the extraction condition of total phenols from lemon peel.The content of phenolic acids in lemon peel were measured by high performance liquid chromatography.The concentration of methanol was 58%,ultrasound power was 154 W,ultrasound time was 15 min,and solid-to-liquid ratio was 1:25,which was the optimized condition.The results of total phenol content was 14.31 mg/g,which the relative standard deviation between the prediction model was 0.6%.?-hydroxybenzoic acid,vanillic acid,?-coumaric acid,ferulic acid,sinapic acid,guaiacol and catechin was measured in the lemon peel,those compounds content range from 8.97 to 36.47 mg/g.(2)Using guaiacol and catechol as substrates to study the determination condition of peroxidase and polyphenol oxidase of lemon pericarp.Futhemore,7 kinds of phenolic acids in the peel were combined with both enzymes.The results showed that the optimum p H values of POD and PPO were 6.5 and 5.5,and the temperature was 35°C,the guaiacol and catechol concentration were 75 mmol/L,0.6 mol/L,respectively.Moreover,the amount of added enzyme were both of 10 ?L.The affinity of POD with seven kinds of phenolic acids in lemon peel was as follows: guaiacol>ferulic acid>vanillic acid,sinapinic acid,?-hydroxybenzoic acid>?-coumaric acid>catechin.However,PPO affinity with main phenolic acids were: catechin>guaiacol>?-coumaric acid>vanillic acid,ferulic acid,sinapic acid,but not reacted with ?-hydroxybenzoic acid.(3)The four-factor and three-level response surface analysis method was used to determine the optimum anti-browning compound film preservation solution based on chitosan,calcium chloride,clove oil and sucrose fatty acid ester.The model was established based on the browning degree and the color difference ?E,meanwhile,the regression equation was obtained.The optimum results which the concentration of chitosan was 1.23%,calcium chloride was 0.30%,clove oil was 0.10%,sucrose fatty acid ester was 0.10%,between prediction results revealed that model was reliable.Because the relative standard deviation of browning degree and color difference ?E between predicted and measured were 3.3%,7.4%,respectively.(4)The effects of fresh-cut lemon slices which stored in different storage temperatures on peroxidase,polyphenol oxidase,phenolic acid and their storage quality were studied.The results demonstrated that 0°C had a good inhibitory effect on the activities of POD,PPO,and slightly influence to the content of 7 main phenolic acids.The phenolic acids content decreased from 0.94 and 10.01 mg/g to 0.65 and 8.87 mg/g after storage 10 day.Moreover,the malonaldehyde content,relative conductivity and DPPH free radical scavenging capacity were 0.35 ?mol/g,64.16% and 91.4%,respectively.On the other hand,the titratable acid and ascorbic acid contents in the juice were 11.6 g/Kg and 33.97 mg/g,respectively.The aroma components of D-limonene,?-pinene and hydrophyllene also have high percentage after 10 days.