Sunday, 21 February 2016

Guinness’s Park Royal Brewery in 1949 – the brew house (part five)

The fermenting house, that’s what’s next. Where all the alchemy occurs as sweet wort transforms itself into beer.

The Fermenting House.—This had to be designed for continuous daily brewings of 3,000 barrels per day. After the appropriate stand in the wort coolers, the wort is run down by gravity through a 5-in. bore main at a rate of approximately 340/400 barrels per hour to centrifugal pumps which pass the wort through a battery of plate-type refrigerators on the third floor of the fermenting house, where it is cooled to the required temperature. On its way to the fermenting tun, the wort is led to glass-lined troughs below the store, or pitching yeast presses, where the required weight of yeast is dropped into the flowing wort prior to its discharge into the fermenting tuns.”
Journal of the Institute of Brewing Volume 55, Issue 5, 1949, page 283.

This is very much like the late 19th-century method of cooling: a few hours in the open cooler followed by a run through the refrigerator. Not sure I’ve heard of mixing yeast with the wort before transferring it to the tun. I know from photos that Whitbread poured bucketfuls of yeast into the fermenter. The Guinness method sounds like a good way of making sure the yeast is distributed through the wort.

This is probably the most surprising paragraph in the whole article.

“There are five 1,260 barrel tuns and six 630 barrel tuns, making a total of 11 in all. This capacity allows three brews to be accommodated simultaneously in the house and still have available one of each size for maintenance and Excise regauging. There are no attemperating coils in the fermenting tuns.”
Journal of the Institute of Brewing Volume 55, Issue 5, 1949, page 283.

Remember that the mash tuns had a capacity of 500 barrels. Meaning the fermenters where larger than the mash tuns. Something I can’t remember ever having seen before in a traditional brewery. The fact that there was only room for three days brewing implies to me that primary fermentation only took three days.

So my guess would be that the fermentation was pretty warm. That the fermenting vessels lacked attemperators would tend to confirm that.  I find that amazing. Attemparators were what made year-round brewing possible at the end of the 18th century. I’d assumed that every brewery had them. Evidently not. So how were they controlling the fermentation temperature? I can’t believe they weren’t keeping it cool somehow.

Though in the early 19th century London brewers fermented Porter very warm. Fermentation often peaked at over 80º F, while Ale fermentations rarely got more than a couple of degrees over 70º F.

I’m not sure I quite get what goes on next. See if you can work it out:

“About 12 hours after the tun is full a certain quantity of gyle is drawn off to storage tanks and kept at a temperature of 40° F. by circulation through plate-type chillers cooled by brine at 25° F. When the desired fall in gravity has been attained, which is usually in about 65 hours, the tunnage is started and the beer is pumped up to the skimmers located on the three top floors of the fermenting house. Originally, the skimmers were fitted with attemperating coils for checking fermentation, but in recent years these have been removed as part of a "cleaning up" programme, and the skimmers now really serve the purpose of auxiliary fermenting tuns, the final cooling being carried out in a battery of plate-type referigerators very similar to the wort refrigerators. The beer is in the skimmer about 24 hours, during which time up to six yeast crops are skimmed off at various intervals, the store or pitching yeast usually being taken from the earlier skimmings. Immediately after the final yeast skimmings the beer is pumped from the skimmers through the beer refrigerators and run down to the storage vats in the vathouse.”
Journal of the Institute of Brewing Volume 55, Issue 5, 1949, page 283.

That first sentence I think I do get, even though it isn’t fully explained. The wort that they’re taking off and cooling sounds like “heading”, wort that was added to later brews as a sort of kräusen. I’m surprised that they were still doing this after WW II.

They confirm that the wort was less than three days in the fermenting tun. Which is quickish, but not crazily fast. Especially as the fermentation was finished off in the skimmers. You know what this sounds like to me? A classic fermentation followed by cleansing system. It sounds like the main function of the skimmers was yeast removal, as with any system of cleansing. I wonder what size and shape the skimmers were?

Note the use of the word “store” for pitching yeast. It turns up regularly in brewing records.

More about the wort refrigerators next.

4 comments:

The Beer Nut said...

You find that usage in "The Guinness Storehouse", their museum in Dublin, which is in a building built for fermenting in.

Anonymous said...

There's photos of skimmers used in 1908:

https://www.guinness-storehouse.com/en/archives/archives-gallery

> brewing > photo 3.

Vaughn S said...

It could be that by chilling the harvest portion of the gyle, they're looking to select for certain characteristics in the yeast crop. Open fermentation and skimming are very temperature-sensitive processes; often cooler fermentations provide a larger weight of yeast per unit of wort produced.

Vaughn S said...

It could be that they're trying to select for certain characteristics in the harvest yeast, such as sensitivity (or lack of) to cooler fermentation temperature. We've found that cooler temperature fermentation also tends to produce more weight of harvestable yeast, per unit of wort produced.