A Practical Treatise on Brewing/Fermentation
FERMENTATION.
The process of fermentation has generally been considered by brewers as very mysterious and uncertain, and over which they have no control. This to a certain extent is no doubt true, for the yeasty heads covering the beer in the gyle-tun during fermentation will assume different appearances according to the fluctuations of the weather, and the seasons of the year. In summer we never see the light yeasty heads in the third change, rising to the fine rocky or alpine appearance which they assume in open frosty weather, nor do the yeasty heads in the fifth change become so close or solid. Windy or hazy weather also affects differently the appearance of the heads of the beer during fermentation.—(See Regular Fermentation.) Over these different appearances, therefore, We have no control, and very likely never shall, unless we could also command the weather. But although we cannot at all times attain the same fine appearances during fermentation, by proper management we can always obtain a sound, regular, and healthy fermentation, and which will invariably produce good beer. We shall now proceed to show how this may be accomplished.
All irregular or unhealthy fermentations arise either by the worts becoming tainted from bad management during some part of the process in brewing, or from positive electro-chemical action, which invariably produces acidity. I should here mention that negative electricity, although it prevents acidity, retards fermentation. In the first place, then, in order to have sound and untainted worts, the greatest cleanliness must be preserved in every stage of the process. First, the mash-tun and under-back should be thoroughly cleaned out, as soon as possible after brewing, the coolers the same. The wort pumps also should be strictly attended to, so that no portion of the worts of a former brewing can possibly be left in them. Very injurious effects are often produced from want of attention to this. Any unnecessary delay in the process of brewing may cause taint or faintness, from the taps being too long in being pumped into the copper. Under the article boiling, charring or carbonizing the worts by high pressure boiling in the copper, is mentioned as another cause of fretful fermentation.—(See cooling the Worts as another cause.) In short, such apparently trifling circumstances often produce such unsoundness, as to prevent the possibility of enumerating them.[1] (For electro-chemical action see Electricity and Want of Uniformity in Beer.)
We are now prepared, however, to assert and prove, that when worts are perfectly sound in all the stages of the process, their fermentation will at all times go on regularly and uniformly, if properly managed, and with sound yeast. The only difficulty, therefore, is, to know when any such unsoundness has actually taken place. A slight knowledge of chemistry will then not only materially assist us in tracing the evil to its cause, but also enable us, in after brewings, to prevent its occurrence, should it even proceed from atmospheric influence. As this evil, however, will sometimes arise, notwithstanding every precaution employed to prevent it, chemistry must be resorted to for enabling us to counteract its baneful effects.
Litmus Paper.
If the brewer have a sensitive smell and taste, they will at all times enable him to judge of the soundness or unsoundness of his worts. But when these cannot be depended upon, litmus paper will be found a very useful substitute. All worts, even when running from the mash-tun, contain a portion of acid, which more or less, according to circumstances, will change the colour of the litmus paper. What we denominate sound worts, will give the paper a kind of dirty brownish red. When we find that the tinge of the paper is a brighter red, there must be additional acid, or perhaps a different acid, produced in some part of the process.
Having thus discovered that an excess of acid has been formed, chemistry must be resorted to for discovering the cause; and when found, we shall be enabled to apply the necessary preventives.
Best Temperature for Vinous Fermentation.
It has been generally found that what may be called a medium temperature during fermentation, has the best chance of producing beer of the proper vinosity and preservative quality. We have seen beer brewed in this country for which the fermentation was carried on at very high temperatures, say from 80° to upwards of 90°. We are also told from very high authority (Professor Liebeg) that the fermentations for Bavarian beer, so celebrated in Germany, are carried on at very low temperatures, say from 42° to 50° F., which could only be done in this country at a very great expense. The first of these, although it answered very well for immediate use, particularly in summer, soon acquired a mawkishness in flavour, and had always a want of vinosity, which, to those unaccustomed to drink it, would not be agreeable. The Bavarian beer that we have seen is precisely similar in these respects. It very much resembles in taste the beer brewed in this country for the Indian market, but neither in vinosity nor flavour would it bear any comparison with the best British beer of a similar description. Having thus given some account of the two extremes, we are still disposed to think that medium temperatures during fermentation, will be found to produce the best beer in every respect. Let us therefore take a range of from 52° to 78° F., thus allowing 26° to be gained during the fermentation, which is enough for the attenuation of any sort of beer when brewed in proper season. We must now keep in mind, that if the proper quantities of good yeast have been employed, (see Yeast,) for every rise of one degree in temperature, there should be a corresponding loss of gravity in the worts of 1 lb. per Long, or 2.78 by Allan’s or Bates’ instrument. For example,—if worts of 42 lbs. gravity per Long be got together in the gyle-tun at 52°, when the temperature rises to 78° they should have lost 26 lbs. of gravity, and thus be attenuated to 14 lbs., when tried by the instrument. We now proceed to describe the appearances exhibited during fermentations of different kinds, and first—
The Regular Fermentation.
We shall now proceed to describe what we consider a sound and regularly good fermentation. In such fermentation, five distinct changes occur, followed, after a certain stage, by a highly pungent aroma, which rises with the carbonic acid gas. If this aroma throughout the process be sound and vinous to the smell, we may feel assured that the worts are sound, and will go on regularly: if, on the contrary, a faintish, disagreeable, sub-acid flavour, arise at any time during the process, we know that acidity or unsoundness has taken place, which should be corrected.
1. The first stage of fermentation commences with a fine white substance like cream, appearing all round the edges of the gyle-tun; this creamy appearance gradually extends over the surface of the fluid in the tun. This we call creamed over, or the first change.
2. The next should be a curly appearance, like the head of a fine cauliflower, which should also extend all over the tun. This, the second change, we denominate the curling or cauliflower head. This cauliflower head should be examined very narrowly, as from its strong and healthy appearance or otherwise, we may pretty nearly judge of the health of the gyle. As above stated, it should have the appearance of a fine cauliflower. If, however, it should assume the appearance of a well curled wig, (we have no better phrase,) having broad flaky curls, it denotes unsoundness. The aroma should now be very perceptible.
3. The curly head should then rise to a light yeasty or rocky head, little more than perhaps from two to three feet high, of a fine brownish white colour if sound. If unsound, it assumes in some parts an ugly bluish-white appearance, which often extends over the tun. This almost invariably happens where there is any galvanic action from chains of pipes, or a mixture of metals; and cannot be cured or prevented, but by doing away with the cause: that is by insulating the tuns.
4. After a time, the light yeasty head should drop a little, perhaps 3 or 4 inches. This we call the 4th change. The aroma should now be very vinous and pungent.
5. The light yeasty head which had dropped, should now rise to what we call a close yeasty head, having the appearance of yeast all over, with many little air bubbles on the top, not, however, larger than a nut or a walnut; these constantly breaking, and others supplying their place. If the fermentation has been healthy throughout, the close yeasty head will continue rising, and puffing out gas from the air bells, until the beer is thought ready for cleansing. This will take place earlier or later, according to the quality of the beer and the public taste. Should all these changes, as before stated, take place regularly, and be accompanied through the process by a sound healthy aroma, (generally termed "stomach,") we may rest assured that all is right, and that the beer, if afterwards properly treated in storing, will turn out sound and good. Sometimes, however, instead of these five changes, not more than three are perceptible, all of them fretful and unhealthy. (These appearances will be more fully treated of, when we describe Irregular Fermentations.) In that case we know that the worts must have been tainted somewhere; the cause of which must be traced and corrected before any successful results can be expected. In most of the brewhouses which we have visited, we have invariably found, that the want of uniformity in fermentation did not arise from the uncertainty, as it is called, of the process, but from one or more of the causes before mentioned. We think, therefore, we are warranted in stating, that fermentations, when conducted on strictly chemical principles, may be carried on with nearly as great uniformity as any other chemical process.
Of Irregular Fermentation.
After what has been said about sound regular fermentations, it may by some be thought unnecessary to describe those which are irregular. There are many brewers, however, as before asserted, who from causes already mentioned, have never had it in their power to see a thoroughly regular and good fermentation. Such are apt to think that all is right, although the contrary may be the case; we, therefore, think it better to describe some kinds which have come under our own observation, and
shall commence with Inert Fermentation.
This is perhaps the most dangerous, because it is the most deceitful. This fermentation, to inexperienced, and even to many experienced brewers, has every appearance of proceeding remarkably well, and they of course think that all is right. The beer, however, will always taste mawkish and heavy, and without vinosity, although the attenuation may have been carried to its proper extent. There can be no doubt of its proceeding from some of the causes of unsoundness already mentioned. It first makes its appearance in the second change, viz. the curling top, which, instead of assuming the fine cauliflower appearance, diverges into long flaky curls hanging downwards; as soon as the "stomach" or smell of the gas begins to rise, a mawkish want of pungency and vinosity is discoverable by those who are acquainted with the proper odour.
The light yeasty head, instead of rising with a rocky appearance, is smooth all over; it, however, often drops regularly, as in a healthy fermentation. The proper close, yeasty head never rises, instead of which, if it does again rise, we have the same frothy appearance as before, smooth all over, with no appearance of air-bells as in a healthy process. The "stomach" also retains the same mawkish want of pungency and vinosity.
We have been thus minute in describing the progress of the above fermentation, because it is the most insidious and dangerous, as also the most common and least known or understood. How often do we hear of mawkishness in the taste which cannot be accounted for. We may rest assured that in nine instances out of ten, it proceeds from the inert fermentation, and not from want of boiling, to which it is generally ascribed.
Before the remedy can be known, the cause must be traced; every experienced brewer will then know how to proceed.
The Boiling Fermentation.
This, to look at, is the most formidable of the irregular forms of the process, and proceeds also from unsoundness in the worts, or occasionally from bad yeast; for which also there is no certain remedy but tracing and removing the cause. It commences, like others, with a creamy top, but the curl rises very light and faint, and in patches over the tun. The light yeasty head has an ugly, bluish-white appearance in some parts of the tun, while in others it has a fretful blistery appearance, and only just covering the beer: this is accompanied with little or no attenuation. The stomach, although sometimes pungent, is neither healthy nor vinous. When the light yeasty head disappears, no other head rises, and the fermentation very soon assumes the appearance of a boiling cauldron.
In the early part of our practice we have had occasion to see a good many boiling fermentations which we could not then account for. Since that time, however, we have been enabled to trace the causes, and invariably to remove them.
Of Close Fermentation.
Many think that fermentation goes on better when the gyle-tuns are accurately closed, so as to prevent contact with the atmosphere. In as far as regards the atmosphere, this opinion is correct; but when fermentation goes on vigorously, there can be no connection with the atmosphere,—the great production of carbonic acid gas excluding it. Carbonic acid gas is heavier than atmospheric air, in the proportion of 1527 to 1000, and while it floats on the surface of the beer, and at the same time is produced in such quantities as to be constantly making its escape, atmospheric air cannot possibly interfere.
About the year 1824, Mr. Gray, of Westham, on Madame Gervas’s principle, attempted to introduce close fermentations into this country. It was tried in several places, but we have never heard of its having been permanently adopted. What may be denominated close fermentations are however, still practised in many parts of the country. When the worts are gathered together in the tun, a certain portion of yeast is added; the gyle-tuns are then shut up as accurately as circumstances will permit, and fermentation is allowed to take its own course, until the yeast falls to the bottom; thus trusting the whole process to chance.
The beer so produced is invariably what is technically denominated foul or yeast-bitten, leaving a nasty disagreeable bitter on the palate; a taste to those unaccustomed to it quite nauseous. It also, like all foul beer, stupifies without exhilarating, and produces, especially amongst sedentary people, heart-burn and head-ache. Custom, however, has so reconciled this unwholesome beverage to the palates of the consumers, that the stupifying quality is thought to proceed rather from the strength of the beer, than from its foulness from the yeast improperly combined with it, or perhaps sometimes from narcotics improperly introduced during the process. We trust, however, that other brewers, by following a more healthy process, and thus producing a better and more healthy beverage, will be able to convince those who follow the above-mentioned unwholesome and erroneous mode of fermentation, that a more scientific process must be adopted.
Of Long and Short Fermentations.
We have always contended that long fermentations are more hazardous than the shorter processes, it being understood that the temperature of the fermenting tuns can be controlled by proper means. It cannot be disputed, that when worts are kept a fortnight, or perhaps more, in the gyle-tun, they are much more liable to be injured by the different atmospheric fluctuations which may take place during that period, both with regard to the influence of electricity and temperature, than they can possibly be in a period of from forty to seventy hours, or sometimes less. If, therefore, equally good, or perhaps even better results, both as to soundness and flavour, can be produced by the shorter process, it must be preferable. It saves both room and expense. Indeed, we have known beer brewed by a short process of fermentation, entirely consumed before beer by the long process was out of the gyle-tun. If worts be partially unsound, and the proper quantity of yeast added for a vigorous fermentation, it will no doubt often lead to the boiling and other erroneous fermentations, which do not, in the slow process, assume an appearance so alarming to the inexperienced brewer as the rapid. We generally find, however, that where the causes of unsoundness have been traced and removed, and the quick fermentations introduced, they have been found to be not only much safer, but to lead to better results than any other, and they, in consequence, have been permanently adopted.
We know that vigorous fermentations always produce the best beer for consumption in warm climates. For stock beers, therefore, which have to stand the summer of this country, the same process will be found the more certain.
Skimming.
At what time the troublesome, tedious, and wasteful process of skimming the yeast off the gyle-tun was introduced, we do not exactly know. We have no doubt, however, that its introduction proceeded from unsoundness in the worts, and consequently fretful fermentations.
By frequently taking off the heads in a fretful fermentation, we no doubt ultimately produce a better appearance. This having been discovered, probably led to the general adoption of that system in certain parts of the country.
A better appearance of the head produced in this way will not, however, tend much to the production of better beer, unless the original cause of the prior ugly appearances have been removed. Indeed, we have seen beer which had been nearly a fortnight in the gyle-tun, undergoing the process of skimming, and having apparently a fine, close, yeasty head, but at the same time smelling and tasting sour. In other instances, we have seen beer left in the gyle-tun to flatten, as it is called; instead of which, however, the beer was gaining heat from a second fermentation, which had distinctly taken place without the brewer being aware of it. The further progress in acidification was then put a stop to, by removing the beer to a colder atmosphere.
Skimming is also attended by a considerable waste of beer, as those who practise it well know. It also generally prevents the possibility of keeping the tun-room clean, splashes of yeast lying all over. We have heard many brewers state their want of confidence in themselves to attempt a vigorous fermentation; and at the same time express their astonishment at seeing it gone through successfully. We are led to conclude, therefore, that inexperience and want of confidence have principally led to the adoption of slow fermentations and skimming.
Fretting Fermentation.
The fretting, or fretful fermentation, proceeds either from using stale or languid yeast. It is often preceded by unsound worts. The first indication is soon after the tun has creamed over. Instead of rising to a curling top, blue patches make their appearance in different parts of the head, and no proper light yeasty change takes place. In about eight or ten hours a sort of undulating motion is apparent all over the top of the Worts, and soon after this the head, which has never been above three or four inches high, begins to drop, and is replaced by large and rather opaque air-bells, which always denote acidity.
There are various ways of making the appearances more healthy. But prevention is better than cure; and, as we have already stated, the causes may be easily traced and removed. The beer so fermented will be either mawkish or yeast-bitten, or perhaps both.
Yeast-bitten Fermentation.
As this term may not be thoroughly understood, we shall endeavour to explain its meaning. Some beer, when drunk, leaves a very unpleasant bitterness on the palate, which hangs there for a considerable time. This bitter taste is supposed by many to proceed from hops; the hop bitter, however, is quite different, being highly aromatic and pleasant, and, technically speaking, goes clean off the palate.
This disagreeable bitterness proceeds from using stale, languid yeast, which, instead of carrying on the fermentation properly, seems to get so incorporated with the beer, as to become a component part of it, which cannot be discharged, as happens after a proper fermentation. Such beer, therefore, must be injurious to all constitutions, but particularly to delicate females and sedentary people. It produces acidity on the stomach, consequently heartburn, and a stupifying effect without exhilarating. Yeast-bitten beer often appears bright enough to the eye, and from this circumstance many people are induced to think it must be good, wholesome drink. The harsh disagreeable bitter, however, which hangs, for a length of time, on the palate, is at once perceptible to any good judge, and warns him against its continued use.
On the Acetous Fermentation.
As the fermentation of malt worts for making vinegar is generally carried on at a much higher temperature, than that commonly used for beer, it has been thought that this high temperature is absolutely necessary for their after acidification; and it probably in some way facilitates that change. This mode of working being peculiar to the manufacture of vinegar, has procured for the process the name of the Acetous Fermentation; but we know, that no more acidity is generated in the gyle-tun during the fermentation for vinegar than in that for beer, unless it proceeds from other causes. It is so far, therefore, only the vinous fermentation of a malt wort, to be converted into vinegar by an after process.
It is even doubtful, however, whether the after process can be properly called a fermentation; for at the time the greatest acidification may be going on, there is often very little appearance of effervescence or fermentation. The fermented wort is converted into vinegar by its being exposed in open vessels, to imbibe oxygen from the atmosphere, and the acidification appears to be accelerated by heat, which is obtained by exposure to the sun in summer, or from stoves in cold weather. But from exposure alone acidity would take place in time without any artificial heat being applied.
We are now treating of vinegar made from malt without reference to that made on the Continent from grapes or wine; but heat we believe is also had recourse to there to accelerate the same process. The vinous fermentation, in vinegar made from every vegetable matter, must, to a certain extent, precede what is called the acetous, as it is alcohol only which imbibes oxygen, and becomes acetic acid.
Chemists inform us that the acetous fermentation may set in during the fermentation of beer, after it exceeds a certain temperature in the gyle-tun; but they cannot afford any chemical proof of this statement. We have seen beer, the fermentation of which was begun at 80° F., and carried to upwards of 90°, and which beer at the end of twelve months bore the test of litmus paper as well as any Bavarian beer that has been met with by us, and this notwithstanding that the latter beer had never exceeded perhaps little more than half that temperature in its fermentation. It is proper, however, to add, that the former beer, as well as all the Bavarian beer which I have seen, wanted vinosity, and had a mawkishness in flavour which would not generally please in this country.
It is well known, and can easily be shown, that positive electricity excites acidity in worts or beer, while negative electricity prevents it. This accounts for the tendency to acidity in all beer which has been subjected to positive electro-chemical action in any part of the process of brewing, but particularly in the gyle-tuns during fermentation.
From what has been said it would appear that there must be some doubt as to whether what is called the acetous fermentation has ever as yet been properly defined; and, with all due deference to much higher authority, it seems at least very doubtful whether the term acetous fermentation is scientifically applicable to any stage of the process of converting beer into vinegar. At all events, no undue acidity takes place in the prior vinous fermentation, unless produced by galvanic action or other accidental causes.
Distiller's Wash.
In confirmation of the above, it may be stated, that distillers in the fermentation of their wash wish to avoid all acidity as much as brewers. It decreases the quantity of spirits from the still in proportion to the extent of acidification which may have been generated. Their fermentations, however, generally speaking, are carried on at as high temperatures, or nearly so, as those used by the vinegar-makers; but when successfully conducted, their fully attenuated wash will bear the litmus test as well as sound beer. When fully attenuated, however, they always find that the sooner they can be brought to the still, the better will be the produce in spirits. It sometimes happens, from accidents or other causes, that their wash cannot be distilled at the proper time, and thus by their being kept too long in the fermenting backs, although kept as much secluded from the atmosphere as possible, acidification begins to supervene, which is indicated immediately by an increase of specific gravity, and the produce in spirits will then be proportionally less and less, according to the time the wash may be thus exposed to atmospheric fluctuations. These few observations are only made in confirmation of what has been above stated; but as this is merely a treatise on brewing, we shall not at present enter further upon the subject, although distillers, from similar causes, are just as likely to be unsuccessful in their fermentations as brewers.
Further Remarks on Fermentation.
It happens sometimes in long fermentations, that although the heads on the worts assume in certain stages very unhealthy appearances, they afterwards, even spontaneously, become more vigorous and healthy; and this the inexperienced brewer assumes as a certain indication that all is right. He may rest assured, however, that if an unhealthy appearance takes place in any part of the process, it denotes either more than the common acidity in the worts, or acidity produced in the process of fermentation by electro-chemical action, or other causes. And, however healthy to appearance the fermentation may become, the beer, instead of being what is denominated “sound old,” will fly off to an acid. This in a great measure accounts for the difficulty of procuring any really sound beer after it has attained a certain age. We have very often, on pointing out some very irregular appearances in certain stages of fermentation, been met by the remark,—“Oh! that is nothing; it will all be quite right before cleansing.” The beer, however, notwithstanding its healthy appearance, will always retain a mawkish, subacid flavour, very disagreeable to those who have accurate palates, and also highly prejudicial to the health of those who drink it.
Many brewers, however, rather than allow their own knowledge of their business to be called in question, will persist in this erroneous mode of working; trusting that their beer will be all consumed before any of the anticipated bad effects can take place. Such brewers obviously look more to their own profits than to the health of the consumers.
Some remarks on Spontaneous Fermentation will be found in the Appendix.
- ↑ It may be proper to state that when acidification commences, fermentation, or perhaps more properly speaking, all further attenuation nearly ceases.