| Apple is a plant fruit of the genus Rosaceae,which is native to temperate regions of the two hemispheres and has a cultivation history of more than 2000 years.China is the world's largest apple producer,accounting for about 57%of the world's total apple output.At the same time,apples are also the fruit with the largest cultivated area and yield in China.Apple is not only rich in nutritional ingredients,but also contains many active and functional ingredients.Polyphenols are an important class of functional ingredients in apples,which play an important role in human health.The effects of different processing treatments on the content,composition,distribution and activity of apple polyphenols were studied in this paper.The summary is as follows.The content,composition,distribution and activity of apple polyphenols were measured and analyzed.The total phenol and total flavonoid content of apples were 20.24 mg/g and 8.81 mg/g.There are four distribution forms of malic acid,which are free phenolic acid,ester-bonded phenolic acid,glycoside-bonded phenolic acid,and methanol-insoluble phenolic acid.The order of the phenolic acid content of the four forms is free phenolic acid>ester-bonded phenolic acid>glycoside-bonded phenolic acid>Methanol-insoluble phenolic acid.Among apple free phenolic acids,the content of chlorogenic acid is the highest,accounting for 98.14%of the total of 8 free phenolic acids,followed by caffeic acid,which accounts for 1.13%,and the other 6 free phenolic acids are very small;the ester bond state among the phenolic acids,the order of the contents of the eight phenolic acids is caffeic acid>chlorogenic acid>gallic acid>ferulic acid>p-hydroxybenzoic acid>orthocatechin>coumaric acid>syringic acid.It accounts for 93.68%of the total,and the last 4 account for 6.32%;the order of the content of the 8 phenolic acids in the glycoside-bonded phenolic acid is chlorogenic acid>ferulic acid>caffeic acid>gallic acid>p-hydroxybenzoic acid>pro Catechin>coumaric acid>syringic acid;among methanol-insoluble phenolic acids,the order of the 8 phenolic acids is chlorogenic acid>gallic acid>protocatechuic acid>p-hydroxybenzoic acid>coumaric acid>caffeic acid>Ferulic acid>syringic acid,the first 4 phenolic acids accounted for 84.77%of the total,and the last 4 phenolic acids accounted for 15.23%.During hot air drying,the total phenol and total flavonoid content of apples gradually increased from 20.24 mg/g and 8.81 mg/g to 47.39 mg/g and 17.38 mg/g,respectively.The content of free phenolic acid and glycoside-bonded phenolic acid gradually increased from 11.77 mg/g and 1.68 mg/g to 28.86 mg/g and 1.91 mg/g,respectively.The content of ester-bonded phenolic acid gradually decreased from 8.39 mg/g to 6.36 mg/g.The content of methanol-insoluble phenolic acid increased first and then decreased,but the overall change was not significant.The FRAP reducing power and ABTS scavenging ability of apple polyphenols gradually weakened with the increase of hot air drying time.During the ultrasonic treatment of apple pulp,the total phenol and total flavonoid content gradually decreased with the increase of ultrasonic power and the prolongation of ultrasonic treatment time.The content of total phenol and total flavonoids in apple pulp was the highest at 200 W and 15 min of ultrasonic treatment which were 37.46 mg/g,14.53 mg/g and 32.35 mg/g,10.14 mg/g respectively.The content of free phenolic acid increased gradually and the content of ester-bonded phenolic acid,glycosidic bonded phenolic acid and methanol insoluble phenolic acid decreased gradually.The FRAP reducing power and ABTS scavenging ability of apple polyphenols increased first and then decreased,they were the highest at 200 W ultrasonic power and 15 min ultrasonic treatment time which were 20.02 ?mol TE/100g,95.33 ?mol TE/100g and 18.84?mol TE/100 g,83.61 ?mol TE/100g respectively.The content of polyphenols and flavonoids decreased first and then increased with the increase of heat treatment temperature and heat treatment time,and the content of free phenolic acids increased gradually from 17.06 mg/g and 19.46 mg/g to 19.46 mg/g and 22.34 mg/g respectively.The contents of ester-bonded phenolic acid,glycoside-bonded phenolic acid and methanol insoluble phenolic acid decreased gradually from 15.21 mg/g,2.02 mg/g,2.39 mg/g and 14.81 mg/g,1.75 mg/g,2.15 mg/g to 14.81 mg/g,1.75 mg/g,2.15 mg/g and 13.73 mg/g,1.57 mg/g,1.84mg/g,respectively.The FRAP reducing power and ABTS scavenging ability of apple polyphenols increased first and then decreased and they were the highest at 60? and 30 min which were 39.35 ?mol TE/100g,79.44 ?mol TE/100g and 35.57 pmol TE/100g,89.95 ?mol TE/100g respectively.The content of total phenol and total flavonoids increased first and then decreased in apple alcohol fermentation.After fermentation,the content of total phenol decreased from 22.08 mg/g to 18.75 mg/g,and the content of total flavonoids increased slightly,from 6.32 mg/g to 7.05 mg/g.The contents of four kinds of phenolic acids increased first and then decreased lightly.The FRAP reducing power and ABTS scavenging ability of apple polyphenols increased first and then decreased.The content of total phenol and total flavonoids decreased gradually from 15.91 mg/g and 4.88 mg/g to 12.14 mg/g and 4.13 mg/g during the fermentation of apple acetic acid.The free-state phenolic acids decreased from 13.75 mg/g and 8.96 mg/g to 11.76 mg/g and 7.16 mg/g respectively,but the contents of glycosidic bonded phenolic acids and methanol insoluble phenolic acids did not change significantly.The FRAP reducing power and ABTS scavenging ability of apple polyphenols decreased from 49.57?mol TE/100g and 63.06?mol TE/100g to 44.81 ?mol TE/100g and 58.05?mol TE/100g respectively. |
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