啤酒的生产过程 - 英语美文欣赏

啤酒的生产过程

[ 录入者:tangigle | 时间:2009-09-08 00:25:44 | 作者: | 来源: | 浏览:343次 ]

The production of Beer(1112words)

Steve Green - 2001.

There are four main ingredients in a real Beer.

WATER - The quantity and variety of dissolved salts in the water used will play a great part in the character of the final beer. The salts play a part in the extraction of fermentable sugars from the grain as well as affecting the way the yeast behaves during fermentation. The total salts in Pilsen's water amounts to around 30 parts per million whereas in Burton on Trent UK, the content is 1220 parts per million. The main salts of interest are as follows; Calcium - increases the extract (efficiency of extracting sugars during mashing). It can also help to make the beer clearer. Sulphates - enhance the bitterness of the hops. It was Calcium Sulphate in the local water in Burton on Trent that helped to create the pale ale style of beer. Chlorides - help to enhance sweetness. These are relatively high in the waters of Dublin and London. This is where Porters and Stouts originated. Part of the modern brewing process involves modifying the content of these key ions to produce a water that is best suited to the style of beer being produced. .

MALT - Grapes can be made to release their sugars simply by crushing. In more Northern latitudes where grapes and sweet fruits do not readily grow ancient people turned to another source. It was probably discovered by accident that as a harvested grain started to germinate, it's sugar content seemed to increase. This was due to the conversion of starches in the grain into sugars as the seed began to germinate. If this process is stopped by drying at an optimal point in this process, the grain will contain some sugars plus a quantity of enzymes to aid the extraction of fermentable sugars. The process of mashing (see below) makes use of these enzymes to do just this job.

HOPS - Winemakers used to add aroma to their wines through adding spices and fruit. The favourite for brewers is to add the flower of the hop vine. When wine makers moved to ageing their wines in oak casks, they discovered that the wood performed a similar job but most modern beers are too light in flavour to cope with this process. The herbs and spices once added to wine also acted as a preservative. The hop cones added to beer also perform very well in this respect. The hops add alpha and beta acids that provide bitterness and aroma to the final product. Hops are chosen for their content in these products as required by the beer being produced. They are also added at different stages in the process depending on whether they are being used to provide bitterness or aroma. Our beers use hops to provide both bitterness and aroma.

YEAST - The first winemakers did not realise the spontaneous fermentation of their grapes was caused by the wild yeasts that collected on the skins of the grapes. Some styles of beers still make use of wild yeasts but as the yeast has such a contribution to make to the character of the final beer, most modern brewers prefer to control the yeast culture. They style of ales we produce uses top fermenting yeast. These are yeasts that form a foam on the top of the beer during fermentation. This foam is skimmed at a certain stage in the fermentation and used to start the next beer fermenting. These yeasts are used at higher temperatures. They are pitched in at around 15 deg C and the fermentation temperature rises as the yeast culture grows. The temperature can rise to 25C or more but must be controlled to prevent undesirable products being produced that can affect the final flavour. The sugar content of the liquid is monitored throughout the fermentation and the process is stopped when the desired alcohol strength is reached.

The Process

The malt is cracked (rolled between precisely set rollers) to just split the grains but not produce flour. This stage is critical as we just need grains that are split to release the sugars and enzymes. Grains that are crushed to a flour prevent the mash from being effective and can block filters etc later in the process. This cracked grain is mixed with water at a precisely controlled temperature of around 67 C. This is a temperature that stimulates the enzymes in the malt to convert starches to sugars that are released into the liquid now called a wort.

A process known as sparging is used to try to maximise the extraction by adding more water until the volume of liquid is correct and then recirculating the wort through the grain. Once the sugar extraction is completed 90-120 minutes, the wort is pumped through to a large boiler known as a 'copper'. The wort is now brought to the boil at which point the first batch of hops is added. Hops added at this stage are for bitterness. Any aroma imparted from the hops added at this stage will be boiled off. The wort is boiled for around 90 minutes before the aroma hops are added and the heat removed. After a short period of time, the wort is rapidly cooled and transferred to a fermentation vessel at around 17 deg C. The yeast is added as soon as conditions are right and fermentation generally starts in a few hours. It is important that the temperature is controlled within tight limits as this affects the fermentation products and hence characteristics of the final beer. After a few days, the sugar content and alcohol content reach a target value and the fermentation is stopped by cooling the beer below the yeast activation temperature. The yeast is removed and the beer is then pumped to conditioning tanks. It remains in these tanks for a few days to mature before being transferred to casks or bottles. Bottling involves an additional process to encourage further conditioning in the bottle. The bottled beer is not filtered or pasteurised so that the beer continues to develop once bottled as long as the environment is suitable. If the bottles are stored upright at 14-17 deg C, the yeast continues to ferment slightly and adds some condition to the beer. This yeast will also fall to the bottom of the bottle so the beer should be decanted in one go to prevent the yeast returning to suspension.

It is the control of this process from start to finish that ensures a high quality product. Realising this, we at 'Le Brewery' make great efforts to carefully control this process so that every bottle tastes as good as the last.


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