# A Practical Treatise on Brewing/Yeast

OF YEAST.
To keep yeast in proper working trim, is a matter of as great importance as any connected with the brewery. That this can be always done, there is not the slightest doubt; and those who assert the ​contrary, only betray their ignorance. We could name brewers who have had no change of yeast for years, (unless when making a long stop,) and their fermentations, have uniformly gone on successfully.
Where fretful and unsound fermentations are going on, the yeast will no doubt also become fretful and unsound. But where the fermentations are sound and healthy, the yeast will be the same, if the proper precautions be taken to keep it so. (See Fermentation—On the Causes of Unsoundness.) How often do we find changes of yeast producing more harm than good, when procured from unhealthy or unsound stocks. If, then, the proper precautions be taken to avoid unsoundness in the worts, there is little doubt but the yeast will go on, doing its work regularly, and no change will be found necessary, unless from a long stoppage of the work.
As yeast, however, is apt to get stale when too long kept, frequent brewings are necessary to prevent its doing so. In summer particularly, the yeast cannot be kept in proper working trim, with fewer than two brewings a week; if more often, the better.
Best Mode of Preserving Yeast.
Yeast, when taken out of the stillions and thrown into tubs or reservoirs, begins to work and fret, thereby expending its strength, and thus becomes unﬁt for carrying on a healthy and vigorous ​mentation in the fluid to which it may be added. Pitching yeast should, therefore, be allowed to remain in the stillions, with a portion of the drawings, until wanted for use: the drawings should then be removed, and the yeast taken up. In the country, where sometimes it is difficult to procure a fresh store of yeast, when required, the best mode of preservation is to place the yeast, when taken up, in the coolest part of the premises, and pour over it the coldest water which can be procured. The water should occasionally be poured off and renewed. If ice can be obtained it is better than water. We generally find that yeast about the second or third day after cleansing is in its best working trim.
Quantities to be used.
It is a very generally received opinion that the stronger the worts, the less yeast is necessary. We cannot, however, subscribe to this opinion, but on the contrary must contend, that if an artificial ferment be at all necessary, the quantity should be proportional to the work it has to do; or, in other words, in proportion to the saccharine matter to be attenuated. A smaller quantity might perhaps ultimately have the desired effect, as we see in very long fermentations; but this is leaving in some degree to chance, what may be effected with certainty, in a much shorter time, by a different, and ​certainly a better process. All sorts of beer, both ale and porter, may be produced equally as good, or perhaps better, by comparatively shorter fermentations, as by the longest now in use: and they will always be found to retain their vinosity and soundness much longer than the others.
The quantities of yeast to be used, however, must necessarily vary according to circumstances. When the worts are got together in the gyle-tun at high temperatures, such as 65° to 70°, less yeast will be necessary than when got together at temperatures which are lower, say from 53° to 60°. If the proper quantity of yeast be applied to sound worts, we generally find that for every degree of temperature gained, the worts will attenuate one pound in gravity by Long’s instrument, or 2.78 by Allan’s and Bates’ instruments; the quantities of yeast to be applied should therefore be so regulated as to preserve this uniformity, which is a sure guide to work by. This rule will not apply, however, where long fermentations are practised.
Many brewers conceive, that by long fermentations, their beer retains more fulness on the palate than with a shorter process. We entirely differ from them, however, on that subject, and maintain that when worts are kept in the gyle-tuns ten to fourteen days or more, the fermentations are much more liable to suffer injury from the atmospherical or other fluctuations which may take place during ​that period, than can possibly be the case in a process of from forty to seventy hours, or even sometimes shorter.
It will always be found also, that beers having undergone a healthy and not too vigorous fermentation, will acquire fulness from age; while on the contrary, those undergoing a long fermentation lose their fulness, and very often become sour.
Many brewers are in the practice of using yeast by measure. This is a very uncertain mode of procedure, as yeast will vary in weight many pounds per gallon. The surest and best mode of applying yeast is by weight, and when we are not thoroughly acquainted with its quality, it should always be mixed with a small portion of worts at a temperature of from 80° to 90°; and should be seen rising in whatever vessel it may have been mixed, before it is added to the worts in the fermenting tun.
When worts are got together in the gyle-tun at a temperature under 60° F., about 1 lb. of yeast to 10 lbs. gravity per Long’s instrument, will be found to produce a loss of 1 lb. in attenuation, for every degree gained in heat. This is a good working rule. When the fermentation (from unsoundness in the worts or other causes) does not go on regularly, the beer is apt to get yeast-bitten; and the quantity of yeast used, is blamed as the cause. This evil, however, more frequently arises from too ​little yeast than from too much. It is impossible to describe by writing, the different anomalous appearances which take place in fermentation, and therefore equally impossible to say what should be done under certain circumstances, unless by personal inspection and examination; when the causes of the different anomalies which take place must be traced, and where unfavourable, rectified, before any permanent improvement can be expected.
Fermentation an Act of Vegetation.
M. Turpin has lately published his observations upon certain phenomena, which he considers sufficient to show, that the act of fermentation concerning which chemists have been so much embarrassed, is owing to the rapid development of infusorial plants. He states that all yeast, of whatever description, derives its origin from the separation from organic tissue, whether animal or vegetable, of special particles of extreme minuteness, which particles, after a certain time, rise to the surface of the fluids in which they are immersed, and there germinate. Their germination is caused by a certain amount of heat, and by contact with atmospheric air. The carbonic acid obtained by fermentation is ascribed to the infusorial plants. M. Turpin considers the act of adding yeast to liquids, when fermentation is languid, equivalent to sowing millions of seeds in a favourable soil. He calls the ​yeast plant of beer Torula cerevisicœ; he considers each infusion to have its peculiar plant, and he names the whole race of such beings Levurians. No doubt the yeast of beer consists of minute molecular matter, the particles of which are globular, and that those particles produce from their sides, other particles like themselves, which eventually separate from the parent, but we do not know that they are therefore plants.
Before the experiments of Mr. Brand, alcohol was by many supposed to be a product of distillation, and not of fermentation. He has, however, satisfactorily proved its existence in the fermented wash, by producing it already formed from that fluid without distillation.
Animalculæ in Yeast.
Other chemists have ventured to declare, that they have discovered living animalculæ in yeast. I here insert Professor Liebeg’s opinion upon these subjects.
“The fermentation of sugar,” says Professor Liebeg, “in contact with yeast, is quite distinct from that of a vegetable juice, or of wort of malt; in the ﬁrst case, the yeast disappears with the sugar, Whilst in the second instance, it is formed during the metamorphosis which the sugar undergoes.
“The form and the nature of these insoluble ​precipitates has suggested to several physiologists very singular views with regard to the nature of vegetation. When yeast of beer, or of wine diluted with water, is examined under the microscope, flattened and diaphanous globules are detected, which are frequently united in groups, and present an appearance of vegetation; others possess the aspect of certain infusoria.
“It would certainly be a very extraordinary phenomenon, if gluten and albumen, which have never been observed in the crystalline state, could assume a geometrical form in the process of the fermentation of wort of malt and vegetable juices. But this does not take place; these substances, on the contrary, separate in the same manner as all those which do not present a crystalline texture in the form of globules, swimming separately, or attached to each other.
“The appearance which they assume, in this instance, has induced certain philosophers to believe that they saw in yeast living organized beings, plants or animalcules, which, for food, assimilate the elements of sugar, and restore it as excretions, in the form of carbonic acid or alcohol. In this manner they explain the decomposition of sugar, and the augmentation of the mass of yeast in the fermentation of malt liquor.
“But this hypothesis destroys itself. In a pure aqueous solution of sugar, the so-called seed ​disappeared with the plants during fermentation; fermentation takes place, the sugar is decomposed at the same time as the yeast, but no appearance of the production and reproduction of the seed of plants and animals, which these philosophers recognise as the agents of the phenomenon, is exhibited.”—(Annales de Chimie, lxxi. 187.)
Whether frequent Changes of Yeast are necessary or not in the Brewery.
When brewers get out of trim (technically so called), or in plainer language, into irregular fermentations, they immediately resort to changes of yeast as the only remedy to put themselves again to rights; such changes, however, are often more detrimental than useful. These irregularities, nine times out of ten, proceed either from tainted worts or atmospherical fluctuations, instead of any failure in the yeast. They cannot, therefore, be immediately remedied, unless by a better process of brewing, or a favourable change of electrical condition.
It often happens that the fermentation takes a favourable turn of this nature before a change of yeast can be had. Notwithstanding this, as effects are often attributed to wrong causes, particularly in the brewery, should the new yeast be used and any improvement follow, it is unhesitatingly ascribed by the brewer to the change, although his ​own yeast from a former brewing, under similar circumstances, might have acted equally well, or even better. It can even be easily proved that almost any yeast, under proper management, and all other circumstances at the same time favourable, may be brought into the best working trim in the course of two brewings; what use then for changes, unless from a total want of yeast by long cessations from brewing.
In combating this argument, we have been met by the assertion that changes of yeast in brewing are equally necessary as changes of seed for land; the latter, however, is a process of nature, while the former is an artificial or chemical process, wherein chemistry can supply all possible deficiencies. In corroboration of what has been said, we subjoin one or two letters from respectable brewers, who have been for years following this system of brewing without any occasion to have recourse to changes of yeast, and whose beer will at all times bear a comparison with that of any of their neighbours. Without reference, therefore, to the opinions of other writers on the subject, we have only further to say, that nothing is here stated but what we have convincing proof of, and are prepared to substantiate by experiment.
Dartmouth, 18th January, 1844.
Dear Sir,—In answer to your query respecting changes of yeast, I have only to say, that so far as I have seen, since pursuing your system of brewing, no change has been wanted,—it is certainly quite unnecessary.
I can easily understand that after any long cessation from brewing, a supply of fresh yeast must. be required,—but in no other case, if your mode of working be strictly adhered to.
I am, yours truly,
John Baker.
Wm. Black, Esq.
Chesham, 15th January, 1844.
Dear Sir,—In reply to yours of the 10th, we are still of the same opinion, that, by your mode of working, a change of yeast is unnecessary, and as a proof of it, we used the same store you first brought with you for more than three years, and the tuns were uniformly healthy and vigorous; but during the last summer, as we were cleansing the brewery, &c., and consequently omitted a brewing or two, we obtained a fresh store, which we are still using with success. Perhaps you will be good enough ​to forward a copy of your new edition, when ready, and we will remit the amount.
We are, my dear Sir, Yours, very truly, Thos and Jas. Nash.
Wm. Black, Esq.
Marine Brewery, Ratcliffe, 9th Jan. 1844.
Dear Sir,—In reply to yours of the 4th instant, we beg to say that we are most decidedly of opinion that changes of yeast are quite unnecessary; in fact, we never have them except we are obliged, which only happens after we have been stopping for repairs.
We feel indebted to you for the compliment you pay to our beers, which we trust will continue to deserve the approbation of a brewer so well calculated to express an opinion.
Wishing you every success in the publication of the Third Edition of your valuable work, of which be pleased to send us a copy when published,
We are, dear Sir, yours very truly, J. and W. S. Holt.
Wm. Black, Esq., 4, Lansdowne Cottages, Islington.