A text-book of the science of brewing : based upon a course of six lectures delivered at the Finsbury Technical College of the City and Guilds of London Institute

Front matter

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TEXT-BOOK

Preface

At the invitation of Professor Meldola, F.R.S., Professor of Chemistry at the Finsbury Technical College of the City and Guilds of London Institute, I delivered at that College, in the winter of 1889, a course of six lectures on the Science of Brewing. At the conclusion of the course, those who had honoured me by their attendance were so good as to suggest to me the desirability of publishing the lectures in book form. On a consideration of that suggestion, I thought that such a publication might perhaps be of some service ; and it was then my intention to limit myself to a re-perusal of the manuscript, and to its publication as such, after only those alterations had been made which seemed necessary from the literary standpoint. On commencing the work, however, I soon came to the conclusion that to continue on those lines would be unsatisfactory : partly because the scope of the work would thus be very limited ; partly because researches published since the date of the lectures threw an entirely new light upon several important matters, more especially upon the products of starch-conversion, and upon the changes occurring during the germination of the cereals. I therefore determined to go over the ground afresh, taking my lectures only as a basis for a more complete and general work than I had at first contemplated. Such a plan, however, involved more leisure than I had at my disposal, and I was obliged to seek assistance. I was so fortunate as to secure the co-operation of rny friend, Dr. G. Harris Morris, who, as the colleague of Mr. Horace T. Brown, F.R.S., had been closely associated a 2

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Preface.

with those researches which have been referred to as throwing fresh light upon phenomena, only partially explicable anterior to their publication. In the introductory remarks, the scope of this work is briefly sketched. We know it to be very imperfect, but we hope that it will not prove entirely useless to those for whom it is intended.

EDWARD RALPH MORITZ.

72, Chancery Lane, London, W.C.

INTRODUCTORY.

The object of this work is to provide in a convenient and accessible form such knowledge of the processes of brewing and the materials employed in that industry, as is at our disposal ; and — so far as we are able — to connect such knowledge with the practice of brewing. We therefore intend it as a text-book in which may be found the results of scientific research together with the practical conclusions which we consider justly deducible from them. We have consequently considered it incumbent upon ourselves to exercise a discretion as to the researches to be included in this work. Apart from those omitted from sheer lack of space, we have purposely excluded those which have been traversed by subsequent investigations, or those which we considered otherwise unreliable. Similarly, we have not hesitated to criticise certain hypotheses still current among practical men when these hypotheses have appeared to us erroneous. In endeavouring to explain practical observations by means of scientific investigations, we have perhaps been guilty of audacity, inasmuch as the explanatory hypotheses we have ventured to put forward may have to be modified as our knowledge extends. But even with this possibility before us, we have thought ourselves justified in doing what we have done. It has seemed to us that the chief value to the practical brewer of such a work as this will lie in the conclusions deducible from scientific researches ; and that, if we refrained from drawing such conclusions, he himself would inevitably do so. While carefully differentiating between exact scientific

V1 hitroductory.

investigations on the one hand, and the conclusions presumably deducible from them on the other, we have thought it only right to take upon ourselves the responsibility of interpreting the experimental evidence, rather than place that responsibility upon our practical readers.

We do not pretend that a perusal of our work will enable a novice to brew beer ; neither will a study of it convert a purely practical man into a chemist. We do not call this work a practical book ; at any rate, it is not “ practical ” in the sense of giving brewers hints or suggestions as to the routine of their operations, or as to the various forms of plant in use. Such knowledge is only to be acquired by experience in the brewhouse, with the assistance of works like that of the late Mr. E. R. Southby, on the ‘ Practice of Brewing,’ to which excellent book we consider this a sort of companion. We do, however, intend this as a practical book in one sense, in so far that it is meant to lead the brewer to a better understanding of what wre may term the physiology and pathology of brewing, and, by so doing, put at his disposal a means for more efficient control over his operations.

We have divided the book into three sections : materials, processes, and analysis. A brief description of what we consider the most reliable methods for the analysis of materials and products has appeared to us essential, and for these reasons : — In the first place, in treating of materials, we have been forced to explain ourselves by a reference to the results of analysis ; and without giving the modes of obtaining them the references would be more pr less obscure. We have also thought that the methods of analysis, illustrated by examples fully worked out, would render the book acceptable not only to those brewers who have laboratories and some scientific knowledge, but also to chemical students interested in technical operations, or such as intend subsequently to interest themselves in these operations. We have presupposed in the analytical section a knowledge of manipu-

Introductory .

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lation, of elementary chemistry, and of ordinary forms of apparatus. We considered that these matters formed no branch of our subject, and that there existed an abundance of text-books adequately dealing with them. We would, however, ask purely practical readers not to entirely ignore the analytical section, for, apart from analytical directions and examples, we have unavoidably had to include in that section much that is of more general interest. Similarly, the first and second section are not very closely demarcated ; we mean that in the first section we have unavoidably had to treat of processes, and in the second section of materials. We have however, endeavoured to meet that difficulty by a system of cross references.

It will be observed by those whose scientific reading is only confined to the trade journals that we have said but little with respect to the albuminoids, or nitrogenous constituents of malts, worts, &c. We are of opinion that the present state of our knowledge of these substances is too restricted to permit of practical deductions ; and on this and other points we have endeavoured to restrain ourselves from putting forth explanatory theories or practical deductions unless sound experimental evidence can be adduced in support of them.

We have freely availed ourselves of all books and journals dealing with the subjects of which we treat, and we have in all cases referred to the original source, not only in common fairness to the author, but for the benefit of those who desire fuller and more complete knowledge on any special points. If we have included work in this book, other than our own, to which we give no reference, we have omitted it unwittingly, and take this opportunity of expressing our regret for that omission. So far as the style is concerned, we are quite aware of its roughness and the entire want of literary polish. We have not, however, sought to correct that defect. We have endeavoured to be lucid, and trust we have succeeded in that limited ambition.

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Introductory.

The work being principally intended for practical men, temperatures are in all cases given on the Fahrenheit scale. In the more scientific chapters, however, the temperatures are given in degrees Centigrade as well as Fahrenheit.

We have to thank many friends for samples supplied for our own investigations, and for the information which they have so freely put before us. We also desire to thank our friends Messrs. Matthews and Lott, for the loan of plates which have illustrated their valuable work on the “Microscope in the Brewery and Malt House,” which work should be consulted on all points specially connected with that department of this industry.

October , 1891.

E. R. M.

G. H. M.

Table Of Contents

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Introductory v

CHAPTER I. Brewing Waters

Classification of brewing waters from the mineral standpoint . . i

I. Waters containing large proportions of gypsum .. .. 3

II. Waters containing small proportions of gypsum, or no

III. Waters containing no gypsum, but sulphates and carbonates of the alkalies .. .. .. .. .. 5

A. Waters containing an excess of gypsum .. .. .. 7

B. Waters containing an excess of common salt .. .. 9

The effect of saline constituents on the character of beers, with

special reference to the brewing of pale bitter ales . . 1 1

The requirements of water for mild ale brewing .. .. .. 25

The requirements of water for stout and porter brewing . . . . 26

Brewing waters considered in regard to their organic purity or

impurity 28

(a) Micro-organisms in brewing water .. .. .. .. 28

(1 h ) Unorganised organic matter .. .. .. 36

The purification of impure brewing waters .. .. .. .. 43

Boiler feed waters . . . . . . . . . . . . . . 49

CHAPTER II. Barley and Malt

Valuation and examination of barley .. .. .. .. .. 55

The morphology and embryology of the barley-grain .. .. 58

Nature of changes during germination .. .. .. .. 67

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Screening, kiln-drying, and steeping .. .. .. .. .. 77

Conditions of healthy germination and drying .. .. .. 81

The storage of malt .. .. .. .. .. .. .. 89

The chemical constituents of barley and malt .. .. .. 91

I. The non-nitrogenous organic compounds .. .. .. 91

Starch and its transformations .. .. .. .. 93

The ready-formed sugars of barley and malt .. .. 133

Non-nitrogenous extractive matters .. .. .. 136

II. Nitrogenous organic substances .. .. .. .. 138

(c) Amides and amido-acids .. .. .. .. 141

(d) The soluble-ferments or enzymes .. .. .. 142

III. Mineral salts (and ash) .. .. .. .. •• 161

The chemical valuation of malt .. .. .. •• •• 163

CHAPTER V. Mashing and Sparging

The temperature of the mashing liquor

The due restriction of diastase in the mash-tun

(a) Condition or after-fermentation

( b ) Body or fulness

(c) Soundness or stability ..

(1 d ) Viscosity and head ..

The excessive restriction of diastase in the mash-tun Conditions other than mash liquor heats affecting the restriction of diastase ..

(a) The influence of heat due to the chemical action of

diastatic conversion

(b) Influence of concentration

(c) Influence of time

(flQ Influence of saline water constituents on diastatic restriction

Restriction of diastase in mash-tun compared with restriction of diastase on the kiln-floors

217 217

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The influence of the type of maltodextrin in wort upon the character of the beer

(a) Conditioning or secondary fermentation ..

(< b ) Soundness (. c ) Flavour ..

CHAPTER VI. The Boiling of the Wort

Objects attained by boiling

(a) The concentration of the wort

ip) The extraction from the hops of their soluble constituents (c) The complete sterilisation of the wort (i d ) The coagulation of the albuminoids (e) The destruction of the diastase and consequent fixation of the starch-conversion products Practical considerations of boiling and of copper construction .. Subsidiary boiling appliances ..

The duration of boiling — single coppers and double coppers

The distribution of hops

The cooling and refrigeration of the wort ..

(a) The lowering of the temperature to the points requisite

for healthy fermentation . .

(b) The aeration of the hot and of the cold wort

(c) The deposition of the glutens and other amorphous

matters

(d) The infection of the wort

CHAPTER VII. Fermentation

Historical

Present views on fermentation The organisms of fermentation

I. The Saccharomycetes, or yeasts (a) Pure culture of yeast ..

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( b ) Advantages derived from the use of pure yeast ..

(c) Physiology and morphology of the alcoholic

ferments

II. The Schizomycetes, or bacteria

(a) Bacillus subtilis

( b ) The butyric acid ferment

(c) Bacterium termo

( d) The lactic acid ferments

(e) The acetic acid ferments

(/) The so-called beer-sarcina ..

(g) Bacillus viscosus

III. The Hyphomycetes or moulds

(a) The Mucors

(d) Penicillium glaucum ..

(c) Oidium lactis . .

(< d ) Monilia Candida

(e) Dematium pullulans ..

(/) Fusarium hordei

Practical considerations Systems of fermentation

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356 360

CHAPTER VIII. The Racking and Storage of Beer

Settling and racking The dry hopping of beer The conditioning of beer The clarification of beer Defective fining of beer

(a) Hop-resin turbidity ..

( b ) Yeast turbidity .. .. .. ..

(c) Bacterial turbidity

( d ) Turbidity of flat beer ..

The bottling of beer

The use of caramel Antiseptics

Interpretation of the analysis and examination of beers

416 418

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Contents.

CHAPTER IX. The Analysis of Water

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Preliminary remarks .. .. .. .. .. .. .. 422

The examination of water .. .. .. .. .. .. 423

(3) Reaction with litmus .. .. .. .. .. .. 424

(4) Microscopic examination .. .. .. .. .. 424

(6) Ammonia — free and albuminoid .. .. .. .. 426

(8) Nitrous and nitric acids .. .. .. .. .. 430

(11) Determination of sulphuric acid .. .. .. .. 437

(12) Determination of silica, alumina, iron, lime, and magnesia 438

(13) Determination of soda and potash .. .. .. .. 441

The combination of acids and bases .. .. .. .. .. 444

CHAPTER X. The Analysis of Malt and Wort

The diastatic capacity of malt .. .. 452

The determination of maltose, dextrin, &c 456

(1) Preparation of the cold-water mash .. .. .. 461

(2) Preparation of the hot-water mash .. .. .. .. 462

(3) Determination of the cupric-reducing power .. .. 463

(4) Determination of the optical activity, or polarimetric

The determination of nitrogen by Kjeldahls method .. .. 465

The determination of moisture .. .. •• •• 467

The determination of acid .. •• •• •• •• •• 468

Contents.

(c) Specific gravity ..

(d) Albuminoids (<?) Ash

(f) Lactic acid

(g) Ready-formed sugars ..

(3) Hot-water mash

(d) Specific gravity ...

( b ) Reducing power ..

( c ) Optical activity

(4) Moisture

The identification and estimation of the maltodextrins

( a ) Determination of maltose in maltodextrins

(b) Determination of dextrin in maltodextrins Wort analysis ..

(1) Optical activity of wort

(2) Determination of maltodextrins

CHAPTER XI. The Analysis of Sugars and Hops

Determination of —

(2) Uninverted cane-sugar

(5) Moisture

(6) Inert carbohydrates ..

(7) Brewer’s extract

Determination of —

(4) Soda and potash

Determination of —

(1) Reducing power

(2) Optical activity

(3) Reducing power and optical activity after fer-

mentation ..

(4) Gallisin

Detection of sulphur in hops ..

Determination of tannic acid in hops

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471 471

475 477

478 481

488 488 490

495 497

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CHAPTER XII. The Analysis of Beer

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Cupric-rcducing power .. .. .. .. •• •• •• 5°4

Degradation with malt-extract .. .. •• •• 5°4

Ash 5°5

The forcing of beer .. .. •• •• •• •• 5°8

(, c ) Microscopic examination . . . . • • • • • • 5 1 3

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V

A TEXT-BOOK

OF THE

SCIENCE OF BREWING.