Preliminary Study On Beer Melanoidins And Its Antioxidant Activity

With the development of beer industry and the improvement of people's living standard,more and more attention has been paid to the study of beer flavor stability.Melanoidin is a brown substance with complex structure in beer brewing process,and its molecular mass is consistent with the degree of polymerization.Melanoidin which has varity of biological and chemical activities is one of the key endogenous antioxidants in beer,and plays an important role in the flavor stability of beer.In this paper,melanoidins isolated from beer by ultrafiltration and macroporous resin chromatography,and then the antioxidant activity of the melanoidin in beer was discussed.In the process of malting,mashing and boiling of barley,we study the formation and accumulation phase of beer melanoidin,to provide theoretical guidance for improving the antioxidant activity of beer.The black beer and lager beer were separated by ultrafiltration,and studied the antioxidant properties of each fraction.The results are as follows: the substance in black beer is the main with molecular weight greater than 10 kDa.This fraction has the highest melanoidin content,ABTS free radical scavenging activity and reducing power,but low metal chelate power.Fraction UF4 in lager beer which is the main component of lager beer had the highest yield,melanoidins content,and antioxidant Activity.The UF4 fraction was further separated into 3 fractions: D1(water eluent),D2(20% ethanol eluent),D3(40% ethanol eluent)by macroporous resin chromatography.The D1 fraction which has the highest yield accounted for almost89% and 94% of the UF4 in black beer and lager beer respectively.But it has low antioxidant activity which is almost 0.The total melanoidin content of UF4 in the fraction D2 was the highest,with the highest antioxidant activity.The changes of malt kilning process of melanoidin content,reducing sugar content,FAN content and antioxidant capacity was studied,and the relationship between them was analyzed,we discovered that the melanoidins content and the antioxidant activity in the process of malt roasting were increasing,and the increase was the highest at 85?.In wort preparation process,the relationship between the melanoidin content and the antioxidant activity in wort was studied.It was found that 45? protein resting resulted in the highest level of the melanoidins content in the wort solids,which was not significant during the subsequent mashing process.Boiling,however,increased the wort melanoidins content by 25%.But the boiling makes the sesame black content increased by 25%,Meanwhile the boiling process significantly reduced the reducing sugar and FAN content,improve the wort ABTS free radical scavenging activity,indicating that wort boiling is the main form stage of melanoidins.