Monday, 15 March 2010

Brewing Sugars

It's ironic that I should spend so much time writing about sugar and defending its use in beer. Why? Because I eliminated refined sugar from my diet when I was a teenager. Beer is the only product containing sugar that I will; consume. Weird, eh?

In the passage below a point is made that I've often seen disputed (especially by know-it-all homebrewers): that more effort is asked of the yeast when sucrose is used because it has to invert it before it can be consumed. It seems to make sense to me, but feel free to argue the opposite. 


Class II.—The necessity of treating cereals, before they could be available as a source of extract in the brewery, led to the wide use of materials, that require no preliminary treatment, which moreover are not acted upon or modified during the mashing process. These articles are the different brewing sugars. They comprise glucose, invert sugar, and cane sugar.

Glucose, or saccharum, as it is sometimes called, is prepared by submitting starch derived from maize, rice, potato, or other source, to the action of acid at a high temperature. The processes involved in its manufacture may be arranged in the following order: (I) The conversion; (2) the neutralisation ; (3) the filtration ; (4) the decolorisation; (5) the concentration; (6) the purification.

(1) The conversion. In this country the materials usually employed in the manufacture of glucose or saccharum are sago, maize, and rice starch. In Germany, potato starch is employed, and in America, green maize. The vessel, in which the conversion is carried out, is termed a converter. It consists of a closed lead-lined iron vessel, provided with stirring gear, manhole, discharging mains, etc. Generally sulphuric acid is used as the converting agent, although other acids may be used. One half of the quantity of acid is mixed with water, and the temperature of the mixture is so adjusted, that it is a little below the gelatinising point of the starch. The acid is then mixed with the starch. The remaining half of the mixture of acid and water is introduced into the converter, and rapidly heated to boiling-point; then the mixture of starch and acid is run in, at such a rate that the temperature does not fall far below boiling. The converter is closed, the stirring gear is set in motion, and the conversion carried to the desired limit. The time for the complete conversion of the starch into glucose varies according to the pressure and temperature in the converter.

(2 and 3) The neutralisation, and filtration. This is effected by mixing chalk with water, and adding it gradually to the solution of sugar. It is generally done in a separate vessel. The neutralised liquid is kept stirred for some time, and is then allowed to settle and run through filter presses, to separate the calcium sulphate.

(4) Decolorisation. The clear, filtered solution is passed through towers packed with animal charcoal.

(5) The concentration is effected in vacuum pans until a specific gravity of 1.50 (water = 1.0) is reached; it is then run into moulds, or casks, and allowed to solidify. The solidified mass is broken up into lumps, in which form it is generally seen on the market. The colour of commercial glucose varies from pure white to light brown, and depends upon the nature of the material used, and upon the extent to which the decolorisation has been carried. The product consists of glucose, varying proportions of dextrin, and water, with small quantities of other sugars.

The manufacture of invert sugar is carried out in a manner very similar to that of glucose. The cane sugar is dissolved in water, and is heated with acid in a converter. The acid is neutralised by chalk, and the filtration, purification by charcoal, and evaporation, are conducted in much the same way as described above. Invert sugar as used in breweries is a syrup pale yellow to dark brown in colour, and consists of invert sugar, water, small quantities of unaltered cane sugar, and mineral matter. Some breweries effect economy by preparing their own invert sugar, either by the acid process, or by heating the solution of cane sugar with yeast at a temperature of 140° F. for three or four hours. The inverting agent in this case is an active principle, or enzyme, known as invertase, contained in the yeast cell. For some kinds of beer, more especially for running porters, raw cane sugar is used; but it is generally advisable to employ invert sugar, as cane sugar is unfermentable, so that in addition to fermenting the other constituents of the wort, the yeast has to invert the added cane sugar. Throwing this extra work upon the yeast tends to weaken it. For this reason, the use of untreated cane sugar is resorted to only in the preparation of certain beers. None but the better-class raw cane sugars are employed."
"The Brewing Industry", by Julian L. Baker, 1905, pages 48-51.

That made a change from all the stuff about 1950's British beer, didn't it? Back to the 1950's tomorrow. Probably.


StringersBeer said...

The idea that sucrose requires "effort" and that other sugars somehow don't is a bizarre one. Glucose and fructose (as I remember from college years and years ago) are just about the only things that yeast will take up off the blocks (as it were). There's a glucose permease which is constitutively expressed - so in a sense that's a free shot for the yeasties. But these simple sugars comprise only a relatively fraction of wort carbohydrates. "Invertase" (which works on sucrose) and "maltose permease" (I think?) are produced as the yeast grows. Import of maltose into the cell is an active process - takes work. In most worts maltose is the biggie.

I wonder what these old brewing chemists meant by "weakening" yeast - and how they measured it?

Graham Wheeler said...

StringersBeer said...
The idea that sucrose requires "effort" and that other sugars somehow don't is a bizarre one.

I agree, both maltose and sucrose are disaccharides and both need to be inverted. Maltose is inverted within the cell, sucrose external to the cell. Indeed, high levels of invert sugar or glucose may well be counter-productive due to things like the Crabtree effect, (which apparently inhibits yeast growth if there is enough of it).

But I am only a know-it-all home brewer, so take no notice of my ramblings.

Graham Wheeler said...

I feel obliged to point out, before someone else does, that I used the term 'invert' inappropriately and loosely. I doubt very much if much if maltose, when split into its component monosaccharides actually bends a beam of light the opposite direction, but you know what I meant.

Aaron J. Grier said...

Beer is the only product containing sugar that I will; consume. Weird, eh?

I don't think consuming refined sugar that went through a yeast counts, unless you consider alcohol a refined sugar. ;)

in the US, high-fructose corn-syrup is much cheaper than cane sugar. I always thought the big guys who used corn used defatted flaked corn, but now I wonder if corn syrup might also be used.

Graham Wheeler said...

but now I wonder if corn syrup might also be used.

Much of the sugar used by the UK brewing industry is maize derived, mostly because the sugar spectrum can be controlled at will. I doubt if it is any cheaper than sucrose-based sugars in the UK.