Tuesday, 12 May 2009


Acid. In particular, acid in beer. It's another area where there's been a great deal of speculation and precious few facts. I'd like to add a few of the latter.

Many contemporary sources tell us of the tartness of Porter and other aged beers in the 19th century. But was this sourness caused by lactic or acetic acid? You may remember my posts last week based on "Food and its adulterations" (by Arthur Hill Hassall, published 1855). The author remarked upon the sourness of Porter and said that it came from lactic acid, the quantity of acetic acid present being negligible.

Here's confirmation of that from a slightly later date, around 1900. My source this time is "A hand-book of industrial organic chemistry adapted for the use of manufacturers, chemists, and all interested in the utilization of organic materials in the industrial arts" by Samuel Philip Sadtler, 1908, page 197. They don't give books snappy titles like that any more. Just as well.

In every case but one (Scotch export, bitter) the acetic acid content is far lower than the lactic acid content. As might have been expected, Dublin XXX Stout has the greatest lactic acid content.

To be fair, when these analyses were perfromed long ageing was out of fashion. I suspect that, had they been done half a century earlier, the level of acidity in the British beers would have been higher.


Nick King said...


I am new to this fantastic blog and so if any of these questions have been answered before then mea culpa. My excuse is lack of time due to exams and gerneral ignorance.

I was wondering what the units are for these acid measurements. All the modern wine ones I deal with are in g/l which I assume these aren't. I can then attempt some maths to get a comparison.

I assume that the acetic acid is present due to the action of acetobactor on alcohol but what is the source of the lactic acid as it can't be the same as wine where it is, in large part, the result of the metabolism of tartaric acid by bacteria.

Also what methods of spoilage control did brewers have available to them back then other than hygiene and keeping Oxygen out as best they could. If the acetic acid levels got too high the beer would surely be undrinkable.

I have loads more questions but I think I have gone on for long enough. I am slowly ploughing through your mini books and other stuff but I keep getting stuck. Can you or any of your readers recommend a good book that outlines the underlying principles of brewing without getting too involved in chemistry.

Back to revising the Italian DOC system now. Joy!

Kristen England said...

These should all be percents.

Multiple % x 10 to get g/L.

Even the Dublin stout at 2.5g/L is still a long way below wine.

Ron Pattinson said...

Nick, as Kristen said, all the numbers in the table are percentages.

All beer contains lactic acid. Some, I believe, comes from the malt itself.

I'm not sure the acetic acid comes from acetobactor if the fermentation has been conducted properly. I thought lactic acid bacteria also produced small amounts of acetic acid.

Hygiene was the main weapon against infection. Lime, steam cleaning, that sort of thing. There's plenty about it in old brewing manuals. It was clearly very important.

I'm not sure what book I'd recommend. I tend to go for the intimidatingly technical ones. H. Lloyd Hind's "Brewing Science and Practice" is very comprehensive. And not too expensive. You should be able to pick up each volume for around $40-50. A more modern brewing manual will knock you back more like $300.

Nick King said...

Kristen and Ron,

Sorry to be so slow in replying I ws at a trade show yesterday and by the time I got home I was knackered. Honestly Ron I don't knwo how you manage to turn out so much material.

Thanks for the detail and I will definately be searching out a copy of the Lloyd Hind book.