Cause and Effect Factors

MEETING HELD at the BALMORAL HOTEL, Edinburgh, on Tuesday, February 27^th , 1906.

Mr. Robert Jeffrey in the Chair.

The following paper was read and discussed:—

Cause and Effect: Factors that Make for Sound and Stable Beers
by W. H. Blake, F.C.S.

During the past half-century scientific investigation has considerably extended our knowledge regarding the agencies of nature which are brought into play in the daily operations of the maltster and brewer, enabling them to some extent to harness, as it were, those powers created for other ends, and to make use of them in effecting their own purposes. Of course these agencies have been utilised empirically by brewers from time immemorial, but the well-known workers in this vast field have lifted a corner of the curtain and shown us how nature performs her work, and under what conditions, and have thereby put brewing on a footing approximating more closely to an exact science. Happily, some of the more prominent of these workers are still living, and are continuing their investigations, others are following in their footsteps, so that our knowledge in this, as in every other branch of science is ever advancing and is continually in a state of unrest It is part of my purpose this evening to trace the connection of these agents with the various operations of the brewer, arid to endeavour to demonstrate how very closely they are associated with the ultimate issue.

My subject is necessarily so comprehensive that it will be impossible to comprise within the limits of a paper suitable for the present occasion more than a very prescribed summary of the relationship between cause and effect in all the operations of the brewer; I will, however, endeavour to apply this relationship in a succinct and practical manner, to the more important of them.

Whilst everything runs smoothly and the even working of the brewery is not checked by one or more of the ever-lurking troubles, whilst the beer is good and sale satisfactory, brewers are prone, to ignore the various agents put into operation in the course of their daily routine, and to overlook their exceedingly delicate organisation, depending for the regular and satisfactory accomplishment of their work upon so many arbitrary factors, often contradictory, always complex; but let the balance of favourable conditions be lowered, malt unsatisfactory, water contaminated, yeast weak or impure, manipulation faulty, or one of many small contingencies arise, and brewers are face to face with a problem bristling with difficulties, dangers, and vexations, involving possibly loss of trade, profit, and repute. Happily the more prominent difficulties are generally readily traced to their origin, and the cause or causes eliminated; it is the smaller troubles, indeed, which are the more vexatious and difficult of diagnosis, troubles connected with intermittent haziness, fretfulness, changeable condition, lack of uniformity, flatness, poor flavour, which really amount to nothing very serious, but cause annoyance to both producer and consumer, and inevitably lead to loss of trade if allowed to continue; troubles that do not really amount to troubles, but are mere grumblings, indicative, however, of the fact that all is not well, that there is a cause lurking somewhere which must be located and removed, that some of nature’s agents are being badly treated, overworked, or underfed, or may be, working under unfavourable conditions of temperature, or, possibly, owing to some blunder in the malting or brewing process, are practically non-existent. Or, again, it will be often found that their work is being neutralised and rendered unavailing by an invasion of other species of nature’s agents, members of an unwelcome nomadic and hostile tribe, whose development and prejudicial work is only possible to any extont where unhealthy and abnormal conditions exist, or where healthy conditions have received a check.

I take it, the aim of every brewer is the production of an article suited to the requirements, palate and otherwise, of the district he operates, and at a cost which will enable him to overcome the competition existing in the area of his operations, possibly to enlarge that area, and, naturally, to leave him a margin of profit.

I shall not concern myself with the many contingencies brewers have to arrange for, such as establishment charges, discounts, bottoms, sometimes their own and genuine (often otherwise), trade losses, and so forth, these all point to the necessity of keeping cost of production within such limits that there may be a wide margin available to meet those many contingencies, with an allowance for a modicum at least of profit. Under latter-day conditions of trading the attainment of this can only be realised by having strict regard to all conditions determining quantity and quality of extract, which naturally involves a thorough knowledge of the ways and means of brewing, together with a keen eye upon brewery economics. To deal first with the causes for and against quantity of extract—the ratio extract actually obtained bears to possible yield is influenced principally by:—

a) Growth of acrospire and rootlets in malt.
b) Grinding.
c) Ratio of water to grist.
d) Mash-tun temperatures and manipulation.
e) The absence of vitrified or unmodified starch.
f) Avoidance of unnecessary loss or waste during all stages, especially those of fermentation and racking.

Excessive production of acrospire or rootlets in malt leads to direct loss of extract, owing to the consumption of starch for their nourishment, which would otherwise be available for extract. The presence of vitrified or unmodified starch in malt presents difficulties in grinding and conversion; it is also, when present to any extent, a cause of “set” mashes. Malt should be graded when necessary, ground uniformly, every corn completely crushed, but not ground to a powder, or difficulties in connection with drainage and brightness will ensue; to accomplish this, type and condition of mill are factors, rolls should be free from pitting and work evenly, bearings and side springs maintained in good order; whether plain or fluted rolls are bettor depends to a great extent on friability and dryness of malt, and whether adjuncts constitute a high percentage of the grist, the difference in their effect being, plain rolls crush the corn, fluted rolls tear it. The latter effect gives better drainage results.

Ratio of liquor to grist has no appreciable effect on quantity of extract, except when a mash is extremely stiff or too thin; when too stiff conversion is restricted, when too thin, sparging liquor is unduly curtailed and much extract may remain uncollected.

Careful adjustment of temperature to the nature of material and type of wort desired is of the first moment in the determination of quantity and quality of extract: too high a temperature was wont to be a frequent cause of set mashes, through partial gelatinisation of starch, too low a temperature may lead to loss by reason of a proportion of the starch remaining unconverted. If spargers fail to deliver equally and uniformly over the surface of goods much extract may remain ungathered, spargers err in this direction by reason of some of the delivery holes becoming enlarged or encrusted with lime from the water, and should be periodically tested by means of a shallow tray divided into partitions, and forming a sector of the circle of the mash-tun. Spargers should deliver the liquor in a fine spray, this enables malt to be ground finer and a larger extract to be obtained, it keeps goods more buoyant, and washes out extract more perfectly.

Injudicious application of sparge-liquor may occasion flooding of goods, and if malt is too finely ground, dead mashes; internal rakes sometimes contribute to this trouble if revolved too rapidly, too frequently, or too long, or they may cause channeling, in other words, the production of fissures in the goods through which sparge-liquor is enabled to escape unaccompanied by any of the ready-formed extract, a not infrequent cause of loss.

It is now usual to obtain the extract held by the hops by sparging or sprinkling rather than by pressure, as was formerly done, to the detriment of the flavour of the wort; when sparging hops it is important to see that the layer of hops completely covers bottom of hop back.

I need not make any lengthy reference to the desirability of keeping the loss attributable to adventitious or preventable causes within the lowest possible limits, by the exercise of every care, the employment of sound plant, the utilisation of barm ale and kindred sources of waste, and the adoption of efficient systems of racking, etc. Where raw and prepared grain form a material proportion of grist, it is highly important that the malt used with it should possess considerable diastatic energy; the employment of raw grain with malt of low diastatic power is a frequent cause of disappointing extracts, it may also lead to dead mashes and their accompanying evils. The thorough admixture of the adjunct and malt is important.

But quantity of extract is of little avail unless quality is satisfactory. In order to meet modern requirements beer should possess the following leading characteristics:—

Absolute and enduring brilliancy, brisk condition, carrying a head of an abiding character, delicate aroma and flavour, bitter, with a pleasing twang of the hop, but which will not remain in the mouth, or sweet, according to class of beer or local demand.

In determining the character of wort, and necessarily the quality of beer, the following are the principal factors :—water, malt and adjuncts, yeast and process.

Water— should be of a definite mineral type, such as that well known as Burton, or gypseous water, which favours the production of a wort containing albuminoids and saline bodies suitable for yeast nourishment, together with carbo-hydrates of a not too readily fermentable type, and malto-dextrins not too easily degradable, and as a consequence stable beers of good character. Soft water determines a wort containing soluble carbohydrates of easy fermentability, with an excess of albuminous matter, and phosphates readily assimilable by yeast, with easible reducible malto-dextrins, the resulting beer being very liable to uncontrollable secondary fermentations. Water of intermediate types will give corresponding intermediate results.

Malt.—Character of malt naturally has a great influence on character of wort, especially in determining flavour, aroma, and brilliancy. The temperature at which malt has been kiln dried greatly influences the composition of wort. Under-cured malt yields amyloins of low type and great fermentability, producing, especially where primary fermentation is incomplete, fretfulness, often violent sickness, in finished beer, imparting a raw flavour, poor condition, and want of character; extreme temperatures, on the other hand, generally produce a malt possessing low diastatic activity, necessitating low initial temperatures with their accompanying dangers, which may take the shape of albuminous turbidity due to excess of albuminous matter of changeable type, fretfulness, and kindred troubles; malt should possess diastatic energy suited to the class of beer to be produced, low percentages of moisture and acidity, and should yield a wort of brilliant character, and one which breaks well on boiling.

Malt adjuncts of both raw and prepared type play an important part in both quality and quantity of extract yield, but only when they are carefully selected, and used in connection with suitable malts.

Sugar, whether raw, with its flavouring characteristics, invert or glucose, possesses a considerable influence on the quality of wort, and enables the brewer to produce a beer which will come into early condition, at the same time it displaces a percentage of albuminous matter, which may or may not be advantageous to the yeast outcrop, according to the class of malt used and type of yeast.

Process.—As I shall deal more fully with process presently, I need here only emphasise its vast influence on beer produced; it has often, been said that while a skilled brewer will produce a good beer from poor materials, an unskilled brewer will produce but a poor beer from good materials.

Enzymes.—In every important stage of brewing, enzymes play a prominent part. These bodies are described by Matthews as “soluble, usually coagulable, albuminoids, possessing a definite property or function, which, broadly speaking, is that of converting insoluble bodies into soluble and diffusible ones.”

Those enzymes possessing the greatest interest for maltsters and brewers are as follows :—

Cytase, developed during malting, possesses the power of dissolving cellulose.

Diastase, the active agent of malt, possesses liquefying and saccharifying properties, the latter property appertains also to the diastase of barley.

One of the principal aims of malting is the development of the former function. Both these properties are utilised in the mash-tun in the conversion of starch.

Peptase, dissolves albumens and renders them diffusible.

Invertase, contained in yeast, possesses the power of splitting up cane-sugar into dextrose and levulose, by hydrolytic action.

Zymase, also contained in yeast, has fermentative power, converting sugar into alcohol and carbon-dioxide.

It now remains for me to review briefly the various stages of brewing, from the point of view of the principal influences leading to the production of beer of a satisfactory type, and to consider some of the causes of deviations from that type.

The three main constituents of wort are—sugar, of a more or less readily fermentable type, to be decomposed during primary fermentation; sugar, of a less fermentable nature, degradable by secondary yeasts and ensuring cask condition; together with albuminous matter, and saline bodies suitable for yeast nourishment, these three constituents must exist in certain definite proportions, varying to some small extent with typo of beer to be produced. The object of mashing is to secure a wort containing these constituents in their proper proportions.

Grinding has some small influence on quality of wort, in that some malts, if ground too fine, produce haziness; malt as prepared for mill should be free from dust, seeds, and other alien bodies, which have a detrimental effect on flavour and quality of wort. When flaked material is used steps should be taken to ensure its thorough admixture, when badly mixed it may bring about drainage and other difficulties.

Whether a portion of the malt is displaced by some other form of starchy material or not, starch is the principal constituent of the grist, and the object of the brewer at the mashing stage is to bring into action the enzyme diastase, the first step in this action being the preparation of the grist by that diastase possessing liquefying power after which the saccharifying diastase effects conversion of starch into maltose and dextrin, in proportion much in accordance with the temperature employed, on the degree of success achieved in this operation will greatly depend the composition and quality of wort produced, certain intermediate bodies are also formed, having a marked potentiality for good or evil according to conversion temperatures, and the temperature at which the malt was kiln-dried. Low conversion temperatures favour a high ratio of maltose, whereas high temperatures favour a high proportion of dextrin, the ratio of one to the other varying with the temperature employed; somewhere between the limits of, say, 145° and 160° F. lies the temperature which should be applied to secure a wort of the desired composition, the exact temperature is chiefly qualified by the condition of starch and diastatic activity of malt; temperature too exerts considerable influence upon the amount and condition of albuminous matter existing in wort, but the quantity and type of those forms of albuminous matter which afterwards go for the nourishment of yeast—amides and peptones—are determined primarily during the germination period of malting.

Unmalted barley contains a very small percentage of peptones, but the action of an enzyme during malting causes a proportion of the albuminous matter to be converted into soluble and diffusible forms or peptones. The use of a percentage of foreign grain favours the presence of peptones and amides.

Having secured a wort of satisfactory type by successful mash-tun operations, the next stage is to submit it to ebullition, in order principally to check further diastatic action, to effect sterilisation and condensation, together with the removal of a certain amount of undesirable nitrogenous matter. I notice that boiling has been the subject of a most interesting and instructive paper read before your section of the Institute comparatively recently, it is therefore unnecessary for me to do more than endorse the author’s remarks as to the influence for good thorough and efficient boiling of wort possesses, and the importance of securing an effective withal, not too prolonged, boil, in order to ensure brilliancy and stability of beer.

At the cooling stage there are one or two points, of apparently small moment, but possessing a potent influence on the successful issue of brewing operations, the hop backs should be so arranged that hops act as an effectual wort filter. A large amount of nitrogenous and resinous matter is removed at this and the cooling stage, and should be held back in hop backs or coolers, the influences on the after fermentation of hot and cold aeration must be regarded and provided for, last runnings from coolers are liable to be thick and to contain much unwelcome resinous and other matter, in which case they should be submitted to filtration before being passed to collecting vessels, but the all-important danger to be guarded against at the cooling stage is that of infection, which may be brought about by various causes, and takes several different shapes, notably bacteria may be introduced from dirty plant, or unwholesome surroundings, wild yeasts are prone to invade the wort, from the near vicinity or even from a considerable distance, or may be lurking on louvre boards and other projections, only waiting a favourable opportunity or a little adventitious assistance to descend upon the contents of coolers or refrigerators. These airborne germs exist in number and type varying with the season of the year, barometric pressure, moist or dry state of atmosphere, direction of wind at the moment, and are influenced to some extent by conditions affecting the purity or otherwise of the air surrounding the brewery and its environment. When influences for evil, such as malt and other mills, certain factories, tanneries, manure heaps, rubbish tips, and so forth exist in propinquity to the brewery, infection may be looked for whenever conditions are favourable for their transmission to brewery and for their development when there. I have been able to trace many serious brewery troubles to one or other of the sources of infection named, taking effect at the cooling stage, especially that attributable to wild yeast. The main precautions to be observed are rapid cooling, wort never being allowed to reach a temperature favourable to the existence of diseased ferments, it should be gathered as quickly as possible under the protective influence of fermentation, in certain cases it is highly advisable to close in coolers and refrigerators, admitting only purified or filtered air. Much contamination may be averted by screening the windward side of coolers, especially when that side happens to be the one from whence infection may be most expected. Malt mills, hay lofts, and similar prolific sources of infection must be completely shut off from cooling and fermenting rooms; louvre boards may well be abolished in modern breweries and methods of admitting air adopted which are under control and more in accordance with modern experience.

During the passage of wort over refrigerators it is again exposed to infection, indeed I had experience of intermittent trouble only last summer from wild yeast infection at this stage, and its very vexatious consequences.

Fermentation may be regarded as one of the most important stages in brewery operations, possibly it should be assigned the primary position. On its successful accomplishment will largely depend the character and stability of beer produced, at the same time character of fermentation is largely governed by the nature of wort prepared in the mash-tun.

The principal changes occurring during fermentation are the conversion of maltose into alcohol and carbon dioxide, together with the assimilation of albuminous matter by yeast, which also requires certain mineral bodies and some loosely combined oxygen to ensure a satisfactory performance of its work, and for its healthy development. It will be obvious, therefore, that to effect a perfect fermentation the constitution of wort must be such as not only to present a proportion of saccharine matter in a condition to be readily acted upon by the primary yeast, but it must also contain albuminous matter in diffusible form—amides and peptones—for its nourishment, together with a small percentage of mineral matter and phosphates to assist in building up the new cells, but the presence of albuminous matter and phosphates in cask favours the production in excess of secondary yeasts, therefore it is desirable that it should be removed by fermentation and yeast reproduction in fermenting vessel.

Yeast is not only in itself a serious source of infection when impure, but its impurity is, to some extent, a measure of impurity or infection existing in water, materials, plant, or at some stage of brewing operations, moreover it must be borne in mind that it is exceedingly, putrescible under conditions favouring putrefaction.

It goes without saying that the yeast used should be vigorous, healthy, and approach as near to purity as is possible under present, conditions of brewing. The pitching yeast employed in this country, under ordinary conditions is made up of a variety of species. Efforts have been made to introduce pure yeast into English breweries, so far with very limited success; it would appear that certain types of secondary yeast are essential to promote flavour and condition in beers brewed in this country, but yeast may also contain types of secondary, and wild yeasts which have prejudicial effects on beer produced, and the purity of yeast as used for pitching must have a marked influence for good or evil.

During fermentation there are one or two important conditions to be observed:—

1. Temperature should increase steadily, not spasmodically, and should be kept within well-defined limits, it usually attains its maximum at about the time the yeast head becomes solid; after fermentation is completed it is better to reduce temperature as rapidly as possible to the limit desired.

2. Attenuation should also proceed steadily.

3. It has been before observed that yeast requires a certain amount of loosely combined oxygen for its healthy action, which is contained in wort at the commencement of fermentation as a result of hot and cold aeration during boiling, cooling and collection, and is afterwards supplied if and when necessary by pumping, or by some form, of aerator.

4. Agitation by rousing or stirring is necessary during the middle and later stages of fermentation; without proper agitation yeast has a tendency to settle to the bottom, where it is obviously unable to accomplish its work; agitation also dispels resinous and other matter which is prone to gather round the cells, and it brings them in contact with their food.

The various stages of fermentation are marked by distinctive heads, n careful observation of these heads will convey to the brewer a very good idea as to whether or not his fermentation is proceeding satisfactorily. As the yeast in its development assimilates or removes a large amount of albuminous matter which is undesirable in a finished beer, the larger the outcrop, within limits, the better. The outcrop normally amounts to some five or six times the quantity of pitching yeast, but it often falls considerably short of this increase, poor development may be due to weakness of yeast, or a scanty supply of nutriment, extreme poverty of development is evidenced in the so-called “fiery” fermentation, and is usually due to lack of yeast nourishment, to slack, acid or unsatisfactory malts, or the application of too high a mash-tun temperature. It does not necessarily follow that the beer will be otherwise than satisfactory, the yeast outcrop being the principal sufferer. In the skimming system it is important that the head or heads should be removed when ready, and whore tuns are fitted with parachutes, the delivery tube of which passes through a stuffing box, the latter is often a source of contamination. At the conclusion of the skimming process it is important to leave a protective covering of yeast. Where the skimming or dropping systems are employed, it is possible to make a careful selection of yeast for pitching purposes by taking only the middle skimmings, the first skimming will contain much dirt and undesirable matter, and the yeast removed towards the close of fermentation will contain many secondary types of yeast, which are produced in the greatest abundance at this stage.

Storage of yeast should receive the greatest consideration; on removal to the store, yeast should be rapidly cooled down, drained when ready, and kept in, preferably, slate backs, out of contact with any possible contamination, at a temperature not much exceeding 50° F,, until required for use.

Pitching yeast should not be too old. When used very young, allowance must be made in calculating the quantity to be used for the admixture of beer it will contain if used before drainage operations are complete, and before being employed for pitching purposes, it should always be examined physically and microscopically as to its fitness and purity. When racking takes place direct from fermenting vessel; unless the inner flange of racking cocks stand well above the bottom of the vessel the last few barrels racked will contain sedimentary yeast, a frequent reason for one or two barrels in each brewing being unsatisfactory ; “thimbles fitting over the cocks are very useful as a preventative, the last few barrels of beer should be passed through filter bags, and may be used for topping up, or worked off in some suitable way.

It would be imagined that hops used for dry hopping, being subjected to no sterilisation process, would introduce undesirable germs to the cask; doubtless they do, but their influence does not appear to be potent for evil; that this is so has been proved by exhaustive experiments, and it is a matter of surprise to many, especially having regard to the fact that fruit trees, more particularly plum, are frequently grown between the rows of hops, notably where a hop garden is about to be grubbed, and we know from Hansen’s investigations on Sacch. apiculatus, that this very virulent secondary yeast is found most abundantly in the neighbourhood of fruit trees, but, so far as I know no serious invasion of this ferment has been traced in English breweries, although it is a frequent source of trouble on the Continent. At the same time, dry hopping hops should be carefully selected as to soundness, as well as quality and flavour.

It is unnecessary for me to call attention to the importance of absolutely filling every cask before passing to cellar.

Having got his beer into casks, the brewer’s cares are by no means at an end. It is true very much beer of running type is consumed before any cask changes have time to come into operation; and if carefully brewed this type of beer answers all the consumer’s requirements in that condition. Much of it, however, especially during warm weather, will undergo cask changes in the consumer’s cellar, in which case its comportment will depend very much upon its treatment there, and upon considerations which I am about to discuss.

With the greater quantity of beer secondary fermentation is most necessary, and in order to be successful it should proceed at a moderate temperature. This cask fermentation is the degradation or breaking down of the complex bodies known as amyloins or malto-dextrins, by the so-called secondary yeasts, which possess the power of fermenting these bodies, and the steadiness and regularity of this fermentation is governed by the type and quantity of amyloins and of the yeasts in question. As appeared when discussing mashing, the typo of amyloins is determined principally in the mash-tun; on the admixture of secondary types with pitching yeast, brewers principally depend for the degradation of these amyloins. We have here, then, two uncertain quantities, which are determining factors in the successful production of beer, and when beers are not satisfactory brewers will do well to enquire into the state of things in connection with these factors.

Beer is never stored for a sufficient length of time to allow of its clarification proceeding naturally, and successful artificial fining is governed more or less by the following influences:

Quantity and type of cask yeast, type of residual extract, steady cask fermentation, nature of suspended matter, temperature when finings are added, quality and modification of finings.

Beer will not fine readily during cask fermentation, and finings act more satisfactorily with a slightly rising temperature; beer that is flat and dead will seldom respond to the action of finings. For bottling beers, filtration leads to a more complete removal of suspended matter.

Having considered the predisposing causes in favour of the production of a satisfactory beer, from the point of view of modern requirements, and the conditions affecting its stability, it will be well to consider, shortly, deviations in one respect or another from the standard adopted. Perhaps the most prevalent of the many diseases to which beer is prone is turbidity, which may be occasioned by a variety of causes, and may vary in degree from a barely discernible opalescence to a revolting puddly thickness. Albuminous and resinous matter may exist in persistent suspension, or may possess little solubility, and be thrown out of solution with a sudden change in temperature or other alteration of the conditions which hold it in solution; low mashing temperatures often lead to this trouble.

The presence of bacteria in beer will determine haziness of a more or less marked naturetheir exceeding minuteness renders impossible their removal by finings; if present in any quantity they, of course, lead to a more disastrous condition of the beer, but the principal source of trouble due to turbidity is fretfulness, determined by several factors, principally by the presence in the finished beer of an excessive quantity of amyloins of an undesirable type; among the causes of fretfulness already referred to in the earlier part of this paper are:

1. The use of unsatisfactory malt or the employment of faulty mash-tun temperatures, leading to the production of worts containing wrong proportions of readily fermentable sugars, and of amyloins of low type, and the restriction of yeast nutriment. Unsatisfactory primary fermentation, limited development of yeast and, consequently, limited assimilation of albuminous matter result from the above.

2. Weak or impure yeast, containing a possible admixture of undesirable secondary types or wild yeasts, or the use of yeast unsuited to water or system of brewing.

3. Wrong adjustment of temperatures and faulty manipulation during fermentation.

4. The presence in the racking sample of too much yeast.

5. Forcing temperatures or extreme cask pressure during storage.

Healthy secondary fermentation must not be mistaken for fretfulness beer is often undergoing cask fermentation at the very time it is required, in which case it is possibly fined: and sent out; the addition of finings and the necessary agitation will often increase cask fermentation into the semblance of a fret, and the finings having been added at an unfortunate period the beer will remain turbid for a considerable time, even after it has become quiescent.

Turbidity is often occasioned by certain forms of wild yeast, which after the cessation of fretfulness cause the beer to remain thick and insusceptible to the action of finings; it will be well at this point to refer to the more important of these saccharomyces from the brewer’s standpoint and their effects—

S. pastorianus.—The most familiar of the secondary yeasts, as being the general cause of cask fermentation; there are three species, two of which may cause violent fret and unpleasant flavour. Yeast bite is also sometimes caused by one of these species.

S. ellipsoideus.—A frequent cause of sickness and stench in beer; in some cases after the sickness has subsided the stench will disappear and the beer be moderately drinkable.

S. exiguus.—A small type of wild yeast, which from its lightness often exists in a state of suspension in beer, causing haziness or cloudiness.

S. minor.—Another small type of ferment frequently found in the examination of yeast, and possessing similar characteristics.

S. coagulatus.—Often found in the deposit of bottled beers, and imparts coarse flavour.

Mycoderma vini.—Gives rise to a greasy film on cask and bottled beers when the vessels are not properly filled or when the beer is exposed.

The next important deviation from a satisfactory beer is in the matter of flavour, good flavour depending upon a number of determining influences, and is more or less involved in the absolute brilliancy, perfect condition, and aroma of the beer; water and malt of suitable quality are the first requirements, and the avoidance of such sources of bad flavour as mustiness, mouldiness, or yeast bite, brought about by the use of impure free steam, obviously impure yeasts, hops that impart a rank bitter flavour, overdosing with sulphites and similar bodies, and a hundred and one smaller influences which will suggest themselves to every practical brewer.

Condition has a decided effect on the flavour and appearance of beer, and depends upon satisfactory cask fermentation and the slow evolution of carbonic acid, which has a marked protective influence on the beer; without the presence of this carbonic acid, which should exist as free and combined in certain definite proportions, beer must needs be flat and impalatable.

Aroma in beer must depend to a great extent on the quality of materials used, especially on hops; beer to be pleasing in appearance must carry a good head, a property which is closely associated with the combined CO₂ and the other important property in beer known as viscosity, which itself is mostly attributable to the hop resins and some of the dextrine.

Body or palate fullness is another important clement, and should exist in accordance with the type of beer and requirements of the district; it depends to a great extent on the quantity and type of remaining extract, and may be imparted artificially by the addition of priming. If when beer is racked it carries a large proportion of readily fermentable sugars, these are speedily removed by certain types of secondary yeast, leading not only to fretfulness, but eventually to premature thinness and flatness. Many people, rightly or wrongly, associate body with depth of colour, and indeed, in some parts of the country, colour is a very important factor in the saleable properties of beer.

Acid beers are not so prevalent as was formerly the case; greater care is exercised in the selection of materials, methods of avoidance of this trouble are more widely disseminated, and undoubtedly greater knowledge is brought to bear on the production of beer; moreover, beer is more rapidly consumed after manufacture, and is not kept long enough for acidity to develop .and take effect. Most brewers are, however, familiar with acidity in beers to a smaller or greater extent during trying weather. Odd casks kept too long under abnormal cellar conditions are wont to be returned as sour, and it is difficult to see how this can be altogether avoided with summer brewed beers under present conditions of brewing in this country.

Acidity is due to the presence of acid-forming bacteria, and exists as acetic, lactic, or butyric acid, according to the species of bacteria present, which bacteria have been introduced as a result of infection from materials, plant, or by air-borne germs, at one of the stages of brewing, and their rapid development in beer is dependent upon and coincides with the presence of unhealthy conditions; that is to say, bacteria may exist in the beer and cause no marked deterioration whilst healthy conditions of brewing obtain, difficulties only arising on the balance of healthy conditions becoming lowered. In this connection I cannot do better than refer you to Pasteur’s well-known work, Etudes sur la Bière, Chapter II, Proposition 1: “Every unhealthy change in the quality of beer coincides with a development of microscopic germs which are alien to the pure ferment of beer”; and its sequel, “the absence of change in wort and beer coincides with the absence of foreign organisms.” This theory, it will he noted, excludes the at one time universal idea that during the summer season electricity was a great cause of unsoundness in beer; directly, it cannot affect the stability of beer, but during the prevalence of thundery weather, beer, and indeed all changeable articles of food, are more liable to undergo change owing to the atmospheric conditions which obtain during such weather, and which are favourable to bacterial infection and development.

In cases of acidity affecting whole brewings of beer, it is well to inquire into purity of water and materials, cleanliness and soundness of plant, mains, and fittings—in my experience most cases of acidity are traceable directly to yeast weakness or impurity, generally to both.

Where odd casks in brewings become acid, the sweetness and soundness of cask plant should be inquired into, also the treatment of returned acid beers during their sojourn in the publican’s cellar.

The forcing tray should not be neglected, as a certain indication of the soundness and stability, or otherwise, of beers, and as a guide to the success or otherwise of the process of manufacture.

I had originally proposed confining my remarks entirely to the diseases of beer, and giving some personal experiences of their diagnosis and treatment, but I thought it more satisfactory to speak of, first, the conditions leading to the production of a healthy beer, then to deal shortly with causes leading to opposite effects; in doing so I found my paper too long to enumerate any personal experiences, which, with your acquiescence, I propose to deal with at some future time.

To many of you, much of the ground I have covered will be familiar, I hope, nevertheless, that I have been able to make my subject interesting, if not instructive. In a paper on brewing nowadays it is difficult to avoid making it so technical, that to a considerable number of practical brewers it lacks interest. I have endeavoured to adhere to the practical side of brewing as far as possible, and only to revert to theory in order to make my meaning clearer.

Discussion.

Mr. Berry said, last summer ropiness was very prevalent, more especially in the south. The trouble was principally confined to bottled beers. Ho would like to ask Mr. Blake if he had read an article in one of the Trade papers in which it was suggested that the barley crop of 1904 might have had something to do with this trouble. Mr. Blake had specially referred to temperatures on the coolers, and he should like to know if he was in favour of shallow coolers or wort receivers. Did the author suggest the use of a fan or some mechanical means of forcing air into the cooler house, and what did he consider a good filtering medium. He particularly referred to the fact that wild yeast or bacteria might be hanging about the cooler room. If he could throw light on that subject he felt sure it would be of interest to all present.

Mr. Blake, in reply, said he had had little experience of ropiness since 1885, until last year, when he met with a good deal of ropy beer. According to one theory the dry season favoured it. It was mostly prevalent in bottled stout, not so much in bottled beer, and was probably attributable to Bact. viscosis, or Sarcina, the infection being air-borne. In regard to cooler temperatures and shallow coolers, he certainly considered that the best cooler was one of copper, say 2 feet deep, so stretched on a frame that the air could have full play; coolers were not so much required as coolers but as aerators. They had to make sure that their wort was properly aerated. In regard to louvres, he laid particular stress on that point because the louvres in a large brewery which he had to do with last year were a serious source of infection. The brewery was within reach of several mills and, among others, a rag-picker’s store. The germs were found to lodge on the louvre boards, and in dealing with the trouble the louvres were altogether abolished and the coolers were laid on a cement floor, rectangular air inlets or holes were made, and the top and walls of the cooling room were treated with a washable substance so that it could be effectively washed down. Cooler infection did not give much trouble in the winter time, but in summer time it was necessary to have some control over the air admitted. During warm weather these holes could be covered by stretching a piece of wetted linen or canvas over them, or by filling them in with a coke filter, steam escaping through a properly arranged aperture in the roof.

Mr. Berry inquired if it was not dangerous to force large volumes of air into the cooling or refrigerating room without filtering it in some way. Was the canvas a good enough filtering medium?

Mr. Blake replied that he did not think it would do to force large volumes of air into cooling and refrigerating rooms. He had never soon it done and he thought it would be dangerous, but many cooling rooms were fitted with fans working internally, causing circulation of air and a ripple on the cooling wort. In regard to refrigerating rooms, the admission of impregnated air during passage of wort over refrigerators was often overlooked, samples taken from pans of refrigerators had been found to be teeming with wild yeasts and bacteria or whatever germs were prevalent in the surrounding atmosphere at the time. Refrigerating rooms were better closed in, or only purified air admitted, many modern breweries had refrigerating rooms so closed in. Canvas could not be regarded as an efficient filtering medium, but it was very much better than nothing.