Fermentation and Bottling
The Action of Yeast
Choice of yeast is most important, for herein lies one of the secrets of successful beer making.
Many people obtain brewers’ yeast from their local brewery and impart to some extent some of the characteristics of the beers turned out by that brewery. Others use dried yeast or bakers’ yeast from doubtful sources, but don’t do this yourself. Far better to get a good yeast from one of the suppliers listed at the end of this book, either top or bottom fermenting kind. Bottom fermenting yeast settles to the bottom of the fermenting vessel; most of this is left behind when the beer is bottled. Any in suspension at bottling time settles to the bottom of the bottles and sticks so hard that all but the merest trace of beer can be poured off clear before the yeast is disturbed.
Many home operators very successfully use yeast from bottled beers. They get a bottle of their favorite stout, or Guinness or Worthington and let it stand overnight. You then pour off the beer very carefully - not into the sink, of course, drink it! leaving about an inch of beer in the bottle. This last inch will contain the variety of yeast used in the beer you have bought. This may be brought into activity by boiling about a quarter pint of water and about an ounce of sugar together. When this is cool pour into the bottle containing the yeast using a funnel. Give a shaking, plug the neck of the bottle with cotton wool and in a day or two or perhaps even in a few hours, this little lot will be fermenting ready to add to the batch of beer you have been waiting to make.
When this batch of beer is nearly finished, you may take a little of the yeast from the top or bottom, treat it as above and you will have a new nucleus ferment readv to add to the next batch when advised in the recipes. You can do this each time you make a batch of beer.
The practice of using yeast from bottled beers can only be done successfully when the beers are dark; this is because only dark beers have a yeast deposit. Bright, light, sparkling ales do not have them.
By the time we add the yeast, sugar will already have been added to the wort in the fermenting vessel. In beer making we add enough sugar to give the amount of alcohol we want and bottle the beer at a point where there is very little sugar left. The fermentation that goes on after bottling charges the beer with the required gas - see draught or bottled beers:
Yeast feeding on the sugar produces alcohol and carbonic acid gas and turns the murky wort into clear foaming beer with a nice percentage of alcohol. The action of yeast has been fully described in various wine books of mine”: it is therefore enough merely to say here that it is the yeast that makes the beer for us, and to explain briefly what happens when yeast is put into the wort. Yeast is a living thing and like all living things it must reproduce itself if it is to survive. When put into a sugar solution - fruit juice in wine making, wort in beer making - it springs to life and almost at once begins to reproduce itself. In so doing it produces alcohol and the gas we see rising in the form of bubbles during fermentation. In wine making, fermentation goes on until so much alcohol is made that the yeast is destroyed by that alcohol. But in beer making we do not want nearly so much alcohol. Therefore, we add just enough sugar to produce the alcohol we want. In wine making we add from two to four pounds of sugar to the gallon. The yeast will use approximately 2~ lb. in producing about 14% of alcohol by volume. This amount of alcohol is usually sufficient to kill the yeast. Therefore any sugar in excess of 2t lb. is left unfermented to sweeten the wine. Obviously, if we use only two pounds of sugar to the gallon the amount of alcohol will be less than 14% and the wine will be dry. The wine will be of 14% and still dry if 2t lb. of sugar is used. If three pounds are used, the wine will still be of 14%, but less dry as there will be half a pound left unfermented to sweeten it.
I mention this to make clear that the more sugar you use the more alcohol you will obtain. But as mentioned, beers should not be too strong; indeed, the amount of sugar given in the recipes is plenty because the amount of alcohol produced from this is ample for beers.
During fermentation a good deal of frothing takes place. This is yeast rising to the surface. Do not disturb unless advised in the recipes in the event of a top fermenting yeast being used.