EVOLUTION OF ANTIOXIDANT ACTIVITY DURING KILNING - ROLE OF INSOLUBLE BOUND PHENOLIC-ACIDS OF BARLEY AND MALT

Phenolic acids, bound to the cellular walls of the germinated barley, are very interesting potential antioxidants of beer. Indeed, the antioxidant activity due to these bound compounds is about 2-fold higher than the activity due to the free phenolic compounds. Seven phenolic acids were separated by HPLC after alkaline hydrolysis of the cake resulting from a methanolic extraction of barley or malt. Three main compounds, trans-ferulic acid, trans-p-coumaric acid, and cis-ferulic acid, were quantified using an external standard method. They respectively represent 177.79, 78.50, and 47.15 mu g/g of dry matter of germinated barley. Responsible for 20-40% of the antioxidant activity of the hydrolyzed cake, they probably have a real influence on the evolution of this activity during kilning.