| Melatonin is the main endogenous antioxidant in beer.It has a strong ability to scavenge free radicals,which has a great impact on the production of beer and the quality of finished beer.The high molecular weight Black sperm contributes much to the antioxidant power of beer.However,the melanoid produced by Maillard reaction and its precursors have the ability of promoting oxidation.The black melanin in beer can catalyze the oxidation of higher alcohols to the corresponding aldehydes.In this paper,we investigated the contribution of melanoid to the antioxidative capacity of beer during beer production and studied the effect of Maillard precursor on the antioxidant capacity and oxidation product in the beer aging process.1.The production of melanin from Malt roasted stage to fermentation stage and its effect on antioxidant activity and hydroxyl radicals of beer were studied by means of beer production test and Maillard reaction model.The results showed that the content of melanin in wort and Maillard model increased with the time of baking time and saccharification time,and the content of melanin after baking at 110 ℃ was significantly higher than that at 86 ℃,And the contents of melanin in the fermented beer did not change significantly.The results showed that the melanoids in beer was mainly produced in the stage of baking coke and saccharification and boiling,and the baking temperature had a significant effect on the fermentation.(P<0.05),and had a significant negative correlation with the peak value of hydroxyl radicals(P<0.05).The results showed that the content of melanin in the wort and Maillard model was positively correlated with the reducing power(RP)(P<0.05).The results showed that the melanin-like substance was involved in the antioxidative reaction during the saccharification and boiling process,especially the hydroxyl radical scavenging.But after 110 ℃,DPPH scavenging rate,and the peak value of solid radicals,and negatively correlated with the TBA value,which indicated that the black spermine could inhibit the formation of carbonyl compounds and had some free radical scavenging ability,so as to improve the antioxidant activity of beer,Which indicates that the oxidation temperature of the baking temperature for the oxidation of beer there are differences.In addition,beer fermentation stage,black melanin content and beer antioxidant activity was no significant correlation,indicating that black-like beer fermentation process is not the main antioxidant.2.The effects of different kinds of beer on the anti-oxidation of beer in 60 ℃ forced aging were studied,and the effect of aging on the aging of beer was studied by externally adding aging substances.The results showed that the content of melanin in different types of beer was different during 10 days of forced aging at 60 ℃,but the content of melanin in different beer was different.At the same time,the TBA values of three kinds of beer all increased continuously during the forced aging,but the DPPH clearance and RP value decreased continuously,which indicated that the antioxidant capacity of the beer decreased during aging,but the content of TBA(P<0.01),and negatively correlated with DPPH clearance rate and RP value(P<0.01).There was no significant correlation between anti-oxidant index and melanin content of domestic black beer,The content of melanin in German black beer was significantly negatively correlated with DPPH clearance rate and RP value,which was significantly correlated with TBA value.Forced aging,the addition of different concentrations of furfural,furfuryl alcohol,furalyl acetate are accelerated aging process of beer.The addition of furfural significantly increased the TBA of all types of beer.The reducing power of beer was decreased obviously by adding furfural to the light beer.The reducing power of the beer was obviously decreased after the addition of furfuryl alcohol.3.The relationship between the contents of eight aging substances and TBA,hydroxyl radical intensity and melanoid content was analyzed by forced aging of the finished beer at 60 ℃ for 10d.The results showed that the content of eight aging substances in the light beer was positively correlated with TBA,hydroxyl radical intensity and melanoid content(P<0.05).The content of aging substances(except 2,4-pentadienoic acid)was positively correlated with TBA and melanoid content(P<0.05).It was found that these aging substances promote the formation of carbonyl compounds,which proves that the melanoids produced by Maillard reaction and its precursors have the ability of promoting oxidation,and these aging substances are also the main precursor substances for producing black melanin.The effects of different conditions on the contents of eight aging substances were studied by forced aging of the finished beer at 60 ℃ for 2 d.It was found that the content of furfuryl acetate and furfuryl alcohol decreased obviously after aging for 2 d with the addition of different concentrations of furfuryl alcohol and furan methyl acetate.The furan methyl acetate might decompose or participate in the final reaction of producing melanoid;The content of furfuryl acetate,furfuryl alcohol,aniline,benzothiazole and 2,4-pentadienoic acid in the aging process of beer were affected by the concentration of ethanol.The results showed that the content of furan,The content of 2,4-pentadienoic acid was affected greatly by the concentration of sulfuric acid in the beer.The content of furfuraldehyde and 2,4-pentadienoic acid were affected by the concentration of salt ion in the beer aging process.The results showed that ethanol could promote the formation of Maillard reaction intermediates and accelerate the aging of beer.High salt ion concentration can promote the formation of aging substances. |
