Sunday, 31 January 2010

Brewing with oats (1943) part two

I don't issue threats lightly. Here's the technical stuff about brewing with oats. One or two of you may find it fun. You weirdoes.

"Flaked Oats
Brewers have now been requested to use flaked oats in their grists, and asa this is a new constituent its technical qualities are of immediate interest. Little need be said of the husky part because oat husks have been in use in a few breweries for many years for the purpose of assisting mash tun drainage, so it is the remaining chief components, namely, starch, protein and fat which require consideration.

First of all one must take into account the flaking process which we understand is the same as that adopted for maize, namely, passing between steam-heated drums. This brings the temperature of the moist oats somewhere about 180º - 200º F., and is likely to have much the same effect on the starch of oats as on the starch of maize: indeed, we should expect it to have a greater effect in rendering the starch more susceptible to the action of diastase because oat starch is an easier convertible starch than maize before such treatment. Anyway, brewers may feel confident that they will get the whole of the starch converted into extract without any change of mash tun procedure. We would add this reminder to those taking the opticity of their worts that just as in the case of maize they should allow an additional one degree for every 4% of oats used, since the oats will not be yielding any extract of low opticity value as malt does. It should be added that equal care in mixing the flaked oats with the grist as intimately as possible is as desirable as with maize flakes.

With respect to protein matter, in the case of maize this is practically insoluble. Hopkins has found a very slight proteolytic action on it in the mash tun, but it was so small as to be insignificant. We may hope for the same with flaked oats, or very nearly so, that the heating has denatured the protein to an extent which renders it unattackable by proteolytic enzyme even under ordinary mash tun conditions. Even if a little is rendered soluble it is unlikely to have a serious technical effect.

As regards the oil or fat in flaked oats, this is very appreciably higher than anything the brewer has so far used in his grists so he would naturally feel suspicious. Fifty years ago authorities insisted on flaked maize keeping its oil percentage down to one and flakes showing as much as 1.5 were condemned. Likewise, about that time the Billing's converter was introduced into this country which used maize grits which were 2% of oil, and objections to it were sometimes raised that the oil would cause turbidity and loss of head on the beer. We have never heard any scientific justification for these opinions. In fact, in those days we knew very little about the causes of haze in beer and as often as not put them down to hop resins. On the other hand, on the principle that there cannot be any smoke without a fire, the accusations against fatty oilin brewing materials made an impression which still lasts. So the question has been as to whether the oil in flaked oats will affect the beer. So far, we understand that it has not been found to have any effect when oats are used at the moderate rate of 10%; although this rate contributes very little to the total fat in the grist yet it is the quality of the fat that matters. Thus, one has heard of oats smelling rancid owing to an oxidation or bacterial action on the fat, but whether this would as readily occur with oats that have been flaked we do not yet know It is to be hoped that the fat in oats will not be troublesome, and on the whole we expect this will prove to be the case."
"The Brewing Trade Review 1943" pages 105-106.

There's still more about oats from the The Brewing Trade Review to come. Just send me 100 euros if you want to be spared it.

1 comment:

Tim said...

Interesting read. My understanding of oil/fats in beer is that they interfere with head formation and retention.

In Michael Lewis' Stout (which I see you reviewed a while back) he writes "When we made an experimental beer with pale malt and 30 percent [rolled] oats, the beer had an unfilterable haze, grainy flavor, and an intensely astringent mouthfeel; it was not a particularly pleasant beer. There was not a unique flavor from the oats."