Abstract

Red and brown Flemish sour beers form a distinct class of Belgian beers obtained by mixed (yeast/lactic bacteria) microbial fermentation and often resulting from blending a 1-to-2-year-old beer with a younger one to obtain a balance between acidic character and sweetness. A detailed composition in volatiles (phenols, lactones, esters, alcohols, acids, …) of three beers representative of the red and brown subcategories is presented. GC data were obtained after different extraction procedures, including solvent-assisted flavor evaporation (SAFE) and headspace. The first results showed the influence of Brettanomyces yeast on the phenol and ester contents. An efficient Brettanomyces activity in the red sour beers (especially in Rodenbach Vintage) was observed, favored by long maturation in wooden casks. This was organoleptically perceived by the horsey flavors brought by 4-ethylguaiacol and 4-ethylphenol, and the solvent-like ethyl acetate through esterase activity. The brown Flemish sour beer (produced in stainless steel fermenters) showed significantly more unreduced 4-vinylguaiacol and 4-vinylphenol, although traces of 4-ethylguaiacol and 4-ethylphenol were also detected (most probably here issued from torrefied malts, as suggested by the opposite substituted phenol/guaiacol ratio).

摘要

红色和棕色佛兰德酸啤酒是比利时啤酒的一个独特类别，通过混合（酵母/乳酸菌）微生物发酵获得，通常是将 1 至 2 年的啤酒与较新的啤酒混合，以获得酸度和酸度之间的平衡。性格和甜蜜。介绍了代表红色和棕色子类别的三种啤酒的挥发物（酚、内酯、酯、醇、酸等）的详细成分。GC 数据是在不同的萃取程序后获得的，包括溶剂辅助风味蒸发 (SAFE) 和顶空萃取。第一个结果显示了酒香酵母对苯酚和酯含量的影响。高效的酒香酵母观察到红酸啤​​酒（尤其是罗登巴赫年份啤酒）的活性，这有利于在木桶中长期陈酿。这是通过 4-乙基愈创木酚和 4-乙基苯酚带来的马味以及通过酯酶活性产生的类似溶剂的乙酸乙酯在感官上感知到的。棕色佛兰德酸啤酒（在不锈钢发酵罐中生产）显示出明显更多的未还原 4-乙烯基愈创木酚和 4-乙烯基苯酚，尽管也检测到了微量的 4-乙基愈创木酚和 4-乙基苯酚（这里很可能是由烘焙麦芽发出的，正如相反的取代苯酚/愈创木酚比例）。