Variability in the Release of Free and Bound Hydroxycinnamic Acids from Diverse Malted Barley (Hordeum vulgare L.) Cultivars during Wort Production

Abstract

Volatile phenols have long been recognized as important flavor contributors to the aroma of various alcoholic beverages. The two main flavor-active volatile phenols in beer are 4-vinylguaiacol and 4-vinylphenol. They are the decarboxylation products of the precursors ferulic acid and p-coumaric acid, respectively, which are released during the brewing process, mainly from malt. In this study, the variability in the release of free and ester-bound hydroxycinnamic acids from nine malted barley ( Hordeum vulgare L.) varieties during wort production was investigated. A large variability between different barley malts and their corresponding worts was observed. Differences were also found between free ferulic acid levels from identical malt varieties originating from different malt houses. During mashing, free hydroxycinnamic acids in wort are both water-extracted and enzymatically released by cinnamoyl esterase activity. Esterase activities clearly differ between different barley malt varieties. Multiple linear regression analysis showed that the release of ferulic acid during mashing did not depend only on the barley malt esterase activity but also on the amount of ester-bound ferulic acid initially present in the wort and on its endoxylanase activity. The study demonstrates the importance of selecting a suitable malt variety as the first means of controlling the final volatile phenol levels in beer.

Antioxidant capacity, arabinoxylans content and in vitro glycaemic index of cereal-based snacks incorporated with brewer's spent grain

“…The soluble conjugated and free phenolic compounds were 14% of the total phenolic compounds analysed, accordingly, the bound phenolic compounds comprised 86% of the total phenolic compounds. This result is in line with those reported where the fraction of phenolic acids ester-bound to arabinoxylans of barley malt was almost integrally found in BSG (Vanbeneden et al, 2007).…”

“…Water soluble phenolic compounds were only 4% of the total phenolic compounds present in BSG. These compounds were expected to be negligible since the free forms of phenolic acids in barley malt were water-extracted during mashing and would have passed into the wort during the beer manufacturing process (Vanbeneden et al, 2007). The soluble conjugated and free phenolic compounds were 14% of the total phenolic compounds analysed, accordingly, the bound phenolic compounds comprised 86% of the total phenolic compounds.…”

“…The degree of arabinoxylan substitution is usually evaluated by the arabinose/xylose ratio, which is typically in the range of 0.4e0.7. The arabinose molecules may be esteried with hydroxycinnamic acids, monomeric or dimeric ferulic acid and p-coumaric acid (Bartolomé, Santos, Jiménez, del Nozal, & Gómez-Cordovés, 2002;Jay et al, 2008;Mussatto et al, 2006;Vanbeneden, Gils, Delvaux, & Delvaux, 2007). Ferulic and p-coumaric acids bound to the cellular walls of the germinated barley grains were pointed as very interesting potential antioxidants (Maillard & Berset, 1995).…”

The Impact of Simple Phenolic Compounds on Beer Aroma and Flavor

“…HCA levels vary among barley varieties, and may be influenced by malting process, growing environment and barley handling post-harvest. Published values vary widely, ranging from 10 to 15 µg/g dry weight combined [9,10] to highs of 100-300 µg/g dry weight for p-coumaric acid, and~400-600 µg/g dry weight for ferulic acid [11,12]. These wide variances may be due to extraction method, analytical methods, and whether free, bound, or all forms of HCAs are analyzed.…”

“…Esterified HCAs are primarily bound to arabinoxylans. Greater than 90% of the HCA in malt is ester-bound, and its availability for malt extraction and later conversion to free HCA is dependent on arabinoxylan-degrading enzymes in the barley, mainly active during the mashing process [11][12][13][14][15].…”