Barms in the sense in which Dan uses the word are a particular development in the evolution of bakers' leavening agents. Historically they come after the use of beer yeast obtained from a brewery, and were in turn superseded by the use of compressed yeast.
The book mentions historical barms being made of malt and hops, but does not go into detail. His simplified recipe for modern readers who don't have malt and hops lying around involves heating up a bottle of real ale and stirring flour into it. This has caused a little confusion, as people assume that the yeast sediment in the bottle has something to do with the leavening of the dough. Actually, the use of a bottle-conditioned beer is something of a red herring.
I do have malt and hops lying around, so decided to try doing the whole thing from scratch. The procedure is similar to making wort for beer up until the wort is drained off the grain. Since the use of barm survived longest in Scotland when bakers in England had moved on to using compressed yeast, I also felt a duty to look into local history.
A small ad in the Scotsman:
BAKER (Foreman) Wanted immediately, competent, to take entire Management and work Parisian Barm. Good wages. Jas. Murdoch, Bonnyrigg.
With the help of some old baking textbooks found online, this one for example, we discover that barm was not universally held in high esteem at the time:
Bread prepared by the aid of barms is generally of poor volume and colour, rather liable to be holey, with dull bloom and texture somewhat variable, but the flavour as a rule is good.
Monica Spiller is someone who has written about barms. However, her method uses malt flour and hot water, so again is not done from scratch.
She has a detailed document with various interesting recipes. Interestingly, it includes a section on sprouting and drying wheat grains. This is, of course, effectively malting them, but for whatever reason she doesn't use the term.
An old domestic science book, Hand-Book Of Household Science by Juniata L. Shepperd suggests:
Yeast which is made with hops is able to overcome the power of foreign ferments longer than that made without hops, because the bitter of the hops is not suited to bacterial growth, but since one can use but little of a yeast made with hops without injuring the flavor of the bread, and a weak yeast acts so slowly as to cause disastrous results, it is better to make yeast oftener without hops, and use plenty of it in bread making.
It is clear from the rest of this document that the author is of the school of thought that considered acidity in bread a defect, but that is by the way:
There is another variety of patent yeast known as "flour barm." This is extensively used in Scotland. The chief peculiarity of bread from this is its decidedly acid taste, thought to be due principally to lactic acid. Much salt is used in making this bread, and it has not the flavor of what, in some other countries, is called the best bread.
William Jago’s classic The technology of bread-making, including the chemistry and analytical and practical testing of wheat flour, and other materials employed in bread-making and confectionery (1911) gives three variations; a compound barm (malt and hops), a virgin barm (spontaneous fermentation, flour and water only), and Parisian barm (malt and flour).
The source is given as a Mr Meikle who was apparently a bakery writer familiar with the Scottish baking trade. Meikle's descriptions are interesting because they show an evolution of practice beginning with, and developing away from, beer-brewing techniques. The first barm mentioned, compound barm, is essentially unboiled wort, made with malt, hops and water, then inoculated with an existing culture (this is the "Store" referred to in the recipe below).
Virgin barm, containing water and flour only, differs from a sourdough starter in that it's made with boiling water. Strictly speaking virgin barm should be allowed to ferment spontaneously, but even in 1911 Meikle was saying he had never actually seen this practice; bakers would add "store". Parisian barm includes malt again, together with scalded flour, but no hops.
Meikle's Parisian recipe:
15 lbs. Water
3 3/4 lbs. Malt } mash at 160º F.
22 lbs. Flour.
35 lbs. Water at 212º F.
10 lbs. Store.
To lie 12 hours before storing or until it reaches 76º F. ; ready 50
The Bread and Biscuit Baker's & Sugar-Boiler's Assistant by Robt. Wells gives a Parisian barm recipe using hops, but it is unfortunately too vague for me to convert the recipe, unless anyone can tell me how much "as much flour as can be nicely stirred in with the barm-stick" is. The basic idea is 1 part malt to 5 parts water for the mash, then add three times as much boiling hop tea.
Why does Wells include hops in Parisian barm and Jago not? I don't know, but I don't see any reason to conclude that one is more "correct." The Meikle-Jago categorisation is pleasingly tidy, but that is not enough in itself to settle the matter.
As mentioned by Shepperd above, one of the reasons to move away from beer yeast in the first place was because the hops made it bitter (it would be fascinating to look into whether this coincides with a shift to using more hops in beer-brewing, thus creating a problem where there had been none before).
On the other hand, barm without hops didn't keep as well. Possibly some bakers just continued using hops and others didn't. It certainly shows that disputes over what is or isn't a poolish, a sourdough, a barm etc. predate internet bread-geek forums.
In part II I will compare a couple of old recipes, convert them to modern units and post the recipe I'm going to use. Part III will involve using the barm to make bread using the quarter-sponge method which was apparently the contemporary method most used.