pubs.acs.org/JAFC Published on Web 12/16/2009 © 2009 American Chemical Society 744 J. Agric. Food Chem. 2010, 58, 744–751 DOI:10.1021/jf903091n Application of a Novel Antioxidative Assay in Beer Analysis and Brewing Process Monitoring STANISLAVA  Z. GORJANOVIC  ,* ,† MIROSLAV M. NOVAKOVIC  , ‡ NEBOJ  SA I. POTKONJAK, † IDA LESKO  SEK-  CUKALOVIC  , § AND DESANKA  Z. SUZ ˇ NJEVIC  † † Institute of General and Physical Chemistry, P.O. Box 551, 11001 Belgrade, Serbia, ‡ Institute of Chemistry, Technology and Metallurgy, P.O.Box 473, 11001 Belgrade, Serbia, and § Faculty of Agriculture, University of Belgrade, P.O. Box 127, 11081 Belgrade, Serbia A novel antioxidative assay based on direct current polarography has been developed. Quantifica- tion of antioxidative (AO) activity has been based on a decrease of hydrogen peroxide anodic current in the presence of antioxidants. An efficient experimental procedure, without any special pretreatment of analyzed samples, has been applied. Antioxidative activity of different kinds of commercial beers (dark, blond, and alcohol-free), some small-scale made special beers with medicinal herbs and mushroom extracts, extracts themselves, as well as individual phenolic components present in beer has been measured. In addition, changes of AO activity during the full-scale industrial process of beer production have been monitored. A strong correlation between results obtained and total phenolics content has been observed. The assay can be recommended for application in brewing industry, either to survey a process with the aim to optimize relevant technological factors or to analyze quality of final product. KEYWORDS: Antioxidative activity; beer; brewing process; DC polarography; hydrogen peroxide; total phenolics content INTRODUCTION Beer is a source of antioxidants (AOs), phenolic compounds originating from barley and hop, readily absorbed, and exten- sively metabolized in humans ( 1 , 2 ). Beer AOs have significant nutritional value, being considered as potential cancer chemo- preventive agents ( 3 -5 ) and promoters of cardiovascular health ( 6 -8 ). Except for a physiological role, the presence of phenolics in beer has technological connotation. The implications of phenolic compounds in relation to the color, the taste, and the nonbiological stability of beer are well-known. Beer rich in AOs has higher quality, more stable sensory characteristics, such as flavor and aroma, and foam stability ( 9 ). Also, it is resistant to oxidation and therefore may have a longer shelf life. Amount of phenolics in beer and wine is comparable ( 10 ). Recent claims suggest that the in vivo AO capacity of beer and red wine are similar despite different concentrations of total poly- phenols, possibly due to superior absorption of the beer phenolics as compared with those in red wine ( 2 , 10 , 11 ). Although beer per drink (of equivalent alcohol content) contains more than twice as many of the AOs as white wine and only half the amount in red wine ( 12 ), the red wine AOs may be larger molecules that are not as readily absorbed as the smaller AOs in beer ( 13 , 14 ). Literature widely describes the content of phenolics in barley, malt, wort, hop, and beer ( 15 -24 ). Approximately 80% of beer phenols are derived from malt and about 20% from hop. The most important phenolic compounds present in beer are phenolic acids (ferulic, cinnamic, chlorogenic, vanillic, gallic, caffeic, o- and p-coumaric, syringic), derivatives of flavan-3-ol (catechin, epicatechin, pro- cyanidin, prodelphinidin) and flavonoglycosides. Antioxidative activity is a significant aspect of beer quality and its evaluation is important either in relation to brewing process optimization or market sale. Over the past few years, the AO activity of beer has been investigated applying numer- ous assays ( 25 -27 ). Methods for determination of AO activity in wort and beer have been reviewed by Karabin ( 28 ). Studies of AO efficiencies of barley, malt, and hop are reported as well ( 29 -34 ). Effect of the malting, mashing, and brewing process on the color, flavor, and content of phenolics com- pounds, as well as AO potential of malt, wort, and beer has been investigated ( 35 -38 ). Generally, commonly used AO assays are rather time-consuming and usually require reactive species. Therefore, a search for low cost and less time-consum- ing parallel methods is of large interest. Development of such a direct and efficient AO assay would be of importance for the food and beverage industry, including the brewing industry. Possibilities of electrochemical techniques within this field have not been fully explored yet. In the present study, we took advantage of direct current (DC) polarography to develop a fast, reliable, and reproducible assay, easily applicable on beer, wort, and mash samples. Antioxidant activity of different brands of commercial beers, some small-scale made special beers with medicinal herbs and mushroom extracts, extracts themselves, as well as individual compounds present in beer, are assessed using the novel assay. In addition, the slightly modified assay has been used for fast monitoring of the full scale *To whom correspondence should be addressed. E-mail: stasago@ yahoo.co.uk. Tel.: þ381 11 21 87 690. Fax: þ381 11 21 80 329.