酿酒业

　　Heady discoveries

　　令人陶醉的发现

　　The yeast that gave rise to lager is tracked down to South America

　　生产拉格（或贮陈）啤酒的酵母可追溯到南美

　　Aug 27th 2011 | from the print edition

　　The Patagonian connection

　　与巴塔哥尼亚高原的联系

　　IN THE 15th century a schism opened in the world of beer. Brewers in Bavaria alighted on a new version of that age-old drink—one that liked to be fermented in the cold and could thus be brewed in winter. The lager revolution had begun.

　　15世纪，啤酒界开始了一次强烈的意见分歧。德国巴伐利亚州的啤酒酿造者们偶然发现这种古老饮料的新变种---一种喜欢在低温发酵，因而能够在冬天酿造饮料。拉格（或贮陈）啤酒革命已经开始。

　　The difference between lagers and more traditional ales lies in the yeast. Ales are made with baker’s yeast, Saccharomyces cerevisiae. Lagers use a hybrid, half cerevisiae and half something else. The interloper, though, has never been found—until now.

　　拉格啤酒和更传统的艾尔啤酒之间的区别在于使用不同的酵母。艾尔啤酒由面包师傅的酵母---酵母属釀酒酵母（学名为Saccharomyces cerevisiae）酿制而成。拉格（或贮陈）啤酒则由一半酿酒酵母和一半其它东西混合而成的东西酿制。不过，这另一半闯入者直到现在才发现。

　　After a worldwide search, a team of geneticists has pinned it down to South America. Chris Todd Hittinger of the University of Wisconsin-Madison and Diego Libkind of the Argentine National Council for Scientific and Technical Research, found their quarry over 11,000km (7,000 miles) from Bavaria, in the cool alpine forests of Patagonia. As they explain in a paper in the Proceedings of the National Academy of Sciences, the newly described species, named Saccharomyces eubayanus, lives in galls that infect beech trees there. These sugary galls often ferment on the forest floor, and locals have been known to make an alcoholic beverage from them. Genetic sequencing confirmed that the yeast in the galls is 99.5% identical with the non-ale half of the lager-yeast genome.

　　在全世界范围内进行搜索后,一队遗传学家已经确认这种闯入者来自南美。威斯康星大学麦迪逊分校的克里斯?托德?希廷格尔（Chris Todd Hittinger）和阿根廷国家科学和技术研究会的迪戈?利布金德（Diego Libkind）在远离巴伐利亚州11000公里（7000英里）的巴塔哥尼亚高原上凉爽的高山森林里找到了他们的来源。根据他们在《美国国家科学院院刊》上发表的一篇论文中所解释，最近描述的这个命名为酵母属真贝酵母（学名为Saccharomyces eubayanus）的物种生活在感染那儿山毛榉树的虫瘿里。这些含糖的虫瘿经常在森林的地面上发酵，当地人一直用它们来酿造含酒精的饮料。基因测序证实了虫瘿里的酵母与拉格酵母的非酿酒酵母那一半基因组有着99.5%的相似性。

　　That solves one mystery but creates another. Human transport is the only way the fungus could have travelled from Patagonia to Europe, but exploration of the New World did not begin until the end of the 15th century, and Patagonia was not reached until the 16th. Yet there are records of cold-fermented beer being made in Munich as early as 1420.

　　这解决了一个秘密，但又产生了另一个秘密。人类的运输是这些真菌能够从巴塔哥尼亚高原传播到欧洲的唯一途径。但是，直到15世纪末，人类才发现新大陆（或世界），而欧洲人一直到16世纪才到达巴塔哥尼亚高原。然而，有些低温发酵啤酒的记录表明，早在15世纪20年代慕尼黑就已生产这种低温发酵的啤酒了。

　　Dr Hittinger suspects lagering in its basic form—lengthy and cool fermentation—did precede the arrival of eubayanus, but that these early lagers were poor. Then, in one batch, eubayanus drifted in and could thrive at the low temperatures which cerevisiae disliked. Brewers favoured that batch, and the yeast spread. Indeed, the historical record provides a hint that something was afoot around this time. In 1553 Bavaria outlawed summer-made beer because wintertime brews had outstripped them in quality.

　　希廷格尔（Hittinger）博士怀疑以其基本形式酿造的拉格（贮陈）啤酒---时间很长而且还是低温发酵---确实比真贝酵母（eubayanus）到来之前发生，但是，这些早期的拉格啤酒质量不太好。 后来，在一批产品中，真贝酵母（eubayanus）漂移出来而且能在釀酒酵母（cerevisiae）不喜欢的低温下茁壮生长。酿酒商们非常喜欢这批产品，之后，这些酵母就蔓延开来了。其实，历史记载提供了一条线索，大约这个时候，有些事情正在进行中。1553年，巴伐利亚州取缔了夏天酿制的啤酒，因为冬季酿造的啤酒质量更好。

　　Eventually, the two yeast strains hybridised to form Saccharomyces pastorianus, the yeast used by lager brewers today. Those brewers will cheer the discovery of eubayanus, as it opens a trove of genes that did not make the transition to pastorianus but which might help the process of cold brewing. One South American beer company is already discussing using pure eubayanus, as well as lab-created hybrids, in a test brew. Whether that will improve the lager’s flavour is another matter. As Dr Hittinger points out, natural selection has done a pretty tasty job already.

　　终于，这两种酵母杂交形成了现在的拉格啤酒酿造商们使用的酵母，即酵母属巴斯德酵母（学名为Saccharomyces pastorianus）。那些啤酒酿造商们将欢呼真贝酵母（eubayanus）的发现，因为它打开了有价值的基因。虽然这种基因没有转变成巴斯德酵母（pastorianus）但它可能帮助低温酿造的过程。一家南美啤酒公司已经在讨论在实验性的酿造中使用纯真贝酵母（eubayanus），还有实验室育制的杂交品种。这种纯真贝酵母（eubayanus）是否提高啤酒品味则是另一回事。因为希廷格尔（Hittinger）博士指出，大自然已经为人类选择了一种非常美味的酒。