Thursday, 6 November 2008

Boiling and cooling 1880-1914

I'm really enjoying "Principles & Practice of Brewing" by Walter J. Sykes & Arthur R. Ling, published in 1907. That's why I'll be pestering you with lots more from it in the coming days.

Today it's the turn of boiling and cooling. Exciting, eh? I was thrilled to discover the method of calculating what proportion of the hops needed to go into the different strength worts. A bit sad, aren't I?

It's interesting to see that heat exchangers ("refrigerators") hadn't totally replaced open coolships, as you might have expected. It seems coolships performed other vital tasks, apart from the mere cooling of the wort.

There were several reasons for boiling:

- sterilising the wort
- destroying disatase
- coagulating and precipitating out proteins (the "break")
- concentrating the wort
- extracting flavour and tannins from the hops

The wort was brought to the boil as quickly as possible to destroy any remaining disatase which would cause the creation of more maltose if left unchecked. The boil was vigourous and varied in length between one hour and more than two. Around 2 hours was commonest.

Whitbread boiled their strong worts for 80 to 105 minutes and their weak worts for 2 hours. Fullers boiled their worts for between 80 and 120 minutes.

Dome coppers had the advantages of aerating the wort and preventing it from boiling over. The disadvantage was that the hops could disintegrate to such an extent that they no longer opperated as a filter for the wort.

There were many different opinions about the best time to add hops to the wort. Some brewers added them as soon as the wort was put into the copper. Others waited until the wort had begun to boil. Sykes & Ling reckoned that it was best to wait until 15 to to 20 minutes into the boil before adding any hops. Their reasoning was that, some proteins already having been precipitated, this helped the precipitative action of tannins in the hops.

They were also proponents of two hop additions: one 15 or 20 minutes after the start, the second 20 to 30 minutes before the end. In this way not all of the volatile oils would be boiled off. The coarser hops were added first and the finer hops, whose flavour would be better preserved, last. A system of three hop additions was also practised, again with the best-flavoured hops added last.

The brewing logs, unfortunately, only give details about the total length of the boil and do not specify when hop additions took place. Based on what appears in brewing manuals, it's probably safe to assume that two additions were commonplace. When hops of different ages were being used, which was usually the case, it would make sense to have used the freshest hops last, as these would contain the greatest quantity of volatile oils. The older hops would have been used as a source of hop resins and tannins, which would not have been lost to such a great extent as the volatile oils during storage.

Though long boiling also extracted some of the less desirable elements of the hops, it was necessary to dissolve hop resins, which acted as a preservative. "The preservative power of hops is dependent on the soft resins they contain, and these, on excessive boiling, undergo a chemical change and are converted into bodies of a less soluble nature; hence hops should never be boiled a second time. It is highly probable that the long periods which hops are often boiled at the present time might be shortened with advantage."

When worts were boiled sepatately, each was hopped in proportion to its volume and gravity. Let's take as an example a brew of 100 barrels of beer, with a gravity of 21 pounds per barrel (1058º) and 250 pounds of were to be used in the whole batch. The total extract would be 100 * 21, or 2100. A first wort of 67 barrels at 24 pounds per barrel, would have an extract of 67 * 24, or 1608. So the amount of hops to be boiled in it would be 250 (total hops) * 1608/2100, or 191.4. The second wort would have the remainder of the hops: 58.6 pounds.

A patented device called a "hop separator", divided hops into leaves, stalks and lupulin. The leaves were added at the start of the boil, the stalks 15 minutes before the end and the lupulin 10 minutes before the end. The inventor claimed between 10 and 25% fewer hops were needed when using this method.

At the end of the boil, the wort was "turned out", that is run into the hop back. The hops settled onto the false bottom and formed a natural filter so that the wort was drawn off perfectly clear. The spent hops were sparged to release any wort retained in them.

Form the hop back, the wort moved on to the coolers. Whilst spread thinly in the shallow coolers, the wort not only rapidly lost heat, but also absorbed oxygen. This oxygen combined chemiccally with some of the contents of the wort. This aeration was vital for the later clarity of the beer.

Whilst in the cooler, the wort deposited a sediment known as "cooler sludge", which was not allowed to get into the fermenting tun. The wort was not allowed to drop below 140º F in the coolers as this would damage the finished beer and make it less stable.

As soon as the wort had dropped in temperature to 140º F, it was run through the refrigerator. Here more oxygen was absorbed, though only in solution, not chemical combination. The wort was cooled to the required pitching temperatuure, usually 58 to 60º F.


Anonymous said...

It's interesting to read that the classic reasons for aerating the wort while hot are the same reasons brewers today try to prevent aeration.

From what I've briefly read, contemporary research indicates that introducing oxygen while hot (+120degF) directly contributes to haziness and poor shelf stability.

Although, it also seems less of an issue for wort made with darker grains as the increased melanoidin levels seem to counteract these supposed oxidation issues.


Kristen England said...

I haven't seen a single study of hot side aeration (HSA). Nothing has ever been proven. There are people that completely swear that it occurs, others that its never a problem for them. What people try to do is take great research from De Clerk and others and apply it to this situation. George Fix was the biggest proponent. This is also the guy who wrote two books that have more circular references between them than any that Ive seen.

What it seems to me is its probably a technique plus ingredient issue over any sort of 'hot side aeration.' The proponents always try to lump it in with the colloidal stability of beer. I know Rochefort splashes the hell out of their hot wort and they don't see any harm.

On top of this, how much splashing around? What type of splashing? Some people say the diameter of your tubing causes HSA. Some say that the use of any sort of pump causes HSA.

I frankly think its all bullocks for the massive majority of brewers. The ones usually worried most about it are the ones who make swill to begin with and are trying to pin it on something etherial. 'Can't be my crappy technique, it has to be HSA.'

Oblivious said...

Ah the hot side aeration debate has even reached here!

Sarah hughes brewery and Rochefort I know of drop the the hot wort into the copper and I have never noticed a problem with Rochefort

Andrew Elliott said...

Amen, Kristen.