Friday, 7 November 2008

Fermentation 1880-1914

I'm still using "Principles & Practice of Brewing" by Walter J. Sykes & Arthur R. Ling, published in 1907 as my source. There's so much goodness in that book that I've had to split fermentation into two parts. Part two will be tomorrow.

Today we'll just be looking at the basics.

In case you're wondering, I've now got 75,000 words of the book done. Which is about half way. At 10,000 words a week, with a following wind I should have the bulk of it polished off by the end of the year. Then I just need to add the stupid jokes.

The amount of yeast for pitching was calculated based on the volume of wort to be fermented and its gravity, stronger beers requiring more. For a wort with a gravity of 1050 - 1055º, 1.5 - 2 lbs per barrel of yeast was needed; for a wort of 1066º, 2.5 to 3.5 lbs; and for worts over 1066º 3 to 4 lbs.

In 1910, according to their brewing logs, Fullers used much smaller quantities of yeast than those just quoted:

AK 0,65 lbs yeast per barrel
Brown Stout 0,94
Porter 0,44
PA 0,67
X 0,74

The yeast used had mostly been harvested from X, though in one case "Mann's Yeast" is specified.

Yeast was either added directly to the wort or first mixed with a quantity of wort at between 65 and 75º F to form a starter. The latter method was a better way of ensuring that a vigorous fermentation started as quickly as possible.

Weaker beers - those with an gravity in the range 1050 to 1055º - were pitched at 58-60º F and ideally not allowed to heat up past 66º F, 70º F at an absolute maximum. Temperatures any higher were too likely to lead to an infection. Strong beers were pitched a couple of degrees cooler and, protected by their higher alcohol content, could be allowed to rise to a maximum of 75º F.

The Fuller's logs from 1910 confirm these pitching and fermentation temperatures. All the worts were pitched at either 59 or 60º F and the maximum temperature reached during fermentation between 66 and 69º F.

If a fermentation were not vigorous enough and the yeast head discoloured, the solution was to "dress" the wort. The old method was to mix 1 lb of wheat flour and 4 ounces of salt per barrel into the wort and then rouse it thoroughly. When the problem was caused by too many unfermentable carbohydrates in the wort, this "dressing" could be effective. The diastase in the malt acted on the carbohydrates, making them more fermentable. The new method was to use just malt flour, without any salt.

The appearance of the head when through a series phases during fermentation:

- after 2-3 hours, bubbles of CO2 began to appear
- after 4-6 hours, a head formed around the edges of the vessel and gradually covered the whole surface
- as the head thickened, it entered the "cauliflower" stage
- next was the "rocky head" stage, when it reached a height of three or four feet
- after about 48 hours the had began to collapse and the "yeasty head" stage began, also known as the "skimming point" as this was when skimming began. It was also when yeast was harvested.

The appearance of the "yeasty head" was an indication that it was time to start cleansing or skimming, if either of these systems of fermentation were being used. The gravity had by now dropped to between a third and a half of the starting gravity.

There were three systems of fermentation:

- the cleansing system
- the skimming system
- Yorkshire squares

But you'll have to wait until tomorrow for a detailed explanation of the fermenting systems.

1 comment:

Kristen England said...

This is quite a nice little video set from Brakspear.

If you click on #7 fermentation it gives you a better idea of the dropping fermentation as Ron describes. The whole thing is good though.