| Apple polyphenols are one kind of important bioactivators in apples, having many kinds of significant physiological functions and a world of exploitation value. In order to realize comprehensive utilization of apple polyphenols, ultrasonic extraction method and macroporous adsorptive resin (NKA-9) were used to extract and purify phenolic compounds from apple pomace; effect of high-voltage pulsed electric fields on apple polyphenol content and antioxidation activity was investigated by HPEF treatment; antioxidant effect of apple polyphenols was studied by evaluations of hydroxy radical scavenging activity, superoxide radical scavenging activity, DPPH radical scavenging activity, nitrite scavenging activity, lipid oxidation inhibiting activity,β-carotin/ linolic acid oxidation inhibiting, and reducing power; enzyme kinetic method was used to investigate inhibitory effect of apple polyphenols on monophenolase and diphenolase activity; agar diffusion method was used in the study of antimicrobial effect of apple polyphenols; gas chromatography-mass spectrometry with easy derivatization method was used for analysis of apple polyphenols; stability of apple polyphenols was evaluated under different conditions (temperature, pH value and vitamin C content) to make better use of them in food products. Results were as follows:(1) The optimum ultrasonic assisted extracting condition of phenolic compounds from apple pomace: extracting solvent 60% ethanol, extracting time 30 min, solid-liquid ratio 1:6 (g/ml), extracting temperature℃60·and extracting once. Under this condition, extraction ratio was 162.253mg/100g, higher than extraction ratio of fresh apple (149.211mg/100g). NKA-9 macroporous adsorptive resin had good adsorption and desorption capability. The optimum dynamic adsorption condition of NKA-9 was as follows:apple polyphenol concentration 2.5mg/mL, pH value 4.5, velocity of flow 1.0mL/min. The optimum desorption condition was as follows:ethanol concentration 70%, velocity of flow 1.0mL/min, desorption volume 10BV. Under these parameters, apple polyphenol purity was 70%.(2) When processing time and electric field intensity were 1500μs and 35KV/cm respectively, apple polyphenol content before preservation was the highest (39.5mg/100mL),8.8% higher than control (36.3mg/100mL, without HPEF treatment); in the same condition, apple polyphenol content after preservation was also the highest (23.2mg/100mL),383.3% higher than control (4.8mg/100mL); when input energy density was 520J/cm3, apple polyphenol content after preservation was the highest (23.4mg/100mL),387.5% higher than control.(3) Apple polyphenols had significant hydroxy radical scavenging activity, superoxide radical scavenging activity, DPPH radical scavenging activity and nitrite scavenging activity, and also significant in reducing power, lipid oxidation inhibiting activity andβ-carotin/linolic acid oxidation inhibiting activity. Apple polyphenols had better effect on hydroxy radical scavenging activity, superoxide radical scavenging activity, nitrite scavenging activity, lipid oxidation inhibiting activity andβ-carotin/linolic acid oxidation inhibiting activity than vitamin C in the same concentration.(4) The concentration of apple polyphenols which caused enzymatic activity loss of 50%(IC50) was 1.0mg/mL for monophphenolase and 0.9mg/mL for disphenolase. Apple polyphenols of 2.0mg/mL extended the lag time in monophenolase from 1.2 min to 4.5 min. An analysis of inhibition kinetics suggested that apple polyphenols was reversible mixed inhibitor for the oxidation of L-DOPA, and the inhibition equilibrium constant for inhibitor was 2.3mmol/L.(5) Apple polyphenols obviously inhibited the growth of six tested bacterial strains including Staphyloccocus aureus. The minimum inhibition concentration of the polyphenols in testing range was 0.6g/L for Flavobacterium SHL45,0.7g/L for Escherichia coli,0.6g/L for Pseudomonas fluorescens SHL5,0.6g/L for Pseudomonas fluorescens SHL7,0.8g/L for Bacillus subtilis, and 0.5g/L for Staphyloccocus aureus, respectively.(6) The optimum condition for derivatization with BSTFA was as follows:polyphenols were derivatized for 30mins at 37.5℃, and the mass ratio of derivatization reagent to sample was 10 to 1. After analysis by Gas Chromatography-Mass Spectrometry,24 compounds were got,11 of which were phenolic compounds and organic acids. Furthermore, four isomeric compounds of epicatechin were separated perfectly.(7) Apple polyphenols after heat treatment had similar concentrations compared to control (without heat treatment). The pH-optimum of apple polyphenols proved to be 5.0, and apple polyphenol concentration in different samples were similar when the pH values of these samples were between 3.0 and 5.0 at 90℃. Apple polyphenols, sugar and heat treatment all had significant effects on vitamin C, when they worked together there were also significant effects except those samples whose vitamin C content were10mg/100mL.
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