"Stout and Porter Grists.—
A proposition advanced in some treatises dealing with the practical side of brewing, namely, that the initial heat for black beers should be low, needs qualification. It has been stated that palate-fulness is thereby brought about, but the tendency will be exactly the reverse, unless lines similar to those suggested on the next page be followed. One might even go so far as to say that in some cases, those for instance where black beers are brewed in comparatively small quantity by country brewers having no large local demand for that class of product, an initial even higher than that used for running ales is required. More than in any other beer is a good firm persistent head a desideratum in black beers, and from what has been said before it will be understood that this is attainable solely by ensuring the presence of a good proportion of dextrin, whether it be combined as malto-dextrin, or free, as was at one time supposed.
And although there is no diastatic capacity in the black or roasted malt, which forms part of the grist, and very little, if any, in the brown and other coloured malts, there is equally no starch in the former, and very little in the latter to undergo hydrolysis, so that the question of the wort's relative poverty in diastase does not come into play, and indeed has no foundation in fact.
There is no doubt that the extraction of a large proportion of albuminous matters, especially in the form of peptones, also tend to give softness and body, if their presence can be secured without the extreme degree of conversion into maltose, which. unless special precautions be taken, they will determine. This might be done by working on lines laid down in an earlier part of this chapter, i.e., by getting a low initial heat and rapidly and considerably raising it (to diastase-crippling point) by free steam, or by some specific modification of the limited-decoction system, or by the employment of the hot-grist process. But failing facilities for these, our own experience makes for higher heats than those used for ales. Similarly, we hold that the "rest" or "stand" after mashing should, if anything, be curtailed.
Black beers are brewed from a mixture of pale, brown, or amber, crystal or chocolate as preferred, and patent, or black, malts, though in Dublin, and we believe in Cork, the brown is omitted. The Irish brewers' patent malt, however, is not the over-roasted black stuff (giving a rough and burnt flavour) which so often does duty for that material in England. It is rather of a rich chocolate brown, and being used in large quantities easily escapes the extreme slackness which samples taken from the country breweries here would often exhibit. Also, as we are given to understand, the brewers in Ireland depend largely, if not solely, upon malt, while in England sugar is considerably used, and that often of very inferior quality, under the questionable idea that anything will do for stout, as the colour covers a multitude of sins.*
* Also it may be added that another characteristic of the Irish system is attenuation pushed to an extreme that the English brewer, who rather aims at keeping a high proportion of unattenuated matter in beer of this class, never dreams of, body and condition being afterwards secured by "worting," i.e., by adding strong wort in incipient fermentation (what the German brewers know as Krausen, anglice Kreising)
"Brewing and Malting" by John Ross Mackenzie, 1927 , pages 253 - 254."
So the idea was to get a dextrinous wort, both for reasons of fulness of body and good head retention. The need for Porter and Stout to have a thick, lasting head comes up time and again in old brewing manuals and other sources. So often, that I'm inclined to believe it. His suggested method of achieving this - a low initial heat quickly raised by steam - looks a bit complicated to me. Mashing at a higher temperature seems a much simpler method.