Jan. II, 1877J 



NATURE 



215 



action. If this be a correct expression it follows that 

 there are two other possible cases where one and three 

 molecules of water are assimilated. Cane-sugar and 

 lactose are isomeric with O'Sullivan's maltose, and are 

 all dextro-rotatory. These three sugars of the formula 

 CjoH^oOii are all fiirther hydrated by the action of 

 diastase, yeast water, and dilute acids. 



Though ignorant of the molecular weights of starch we 

 may yet safely assume in the expression (QHioOs)^ that 

 the value of n must be large, and that a molecule of such 

 complexity will yield in addition to dextrine several 

 sugars isomeric with sucrose and with dextrose, and it 

 may be others of greater hydration. In the brewer's 

 mash tun the hydration products vary according to the 

 malt employed and the extent to which the malting pro- 

 cess is pushed before the kiln drying action, the more of 

 the active ferment formed the greater the hydration in a 

 given time. The amount of water is an important factor 

 in the hydration process ; the greater this is within certain 

 limits the greater the hydration ; and lastly, the products 

 vary with the amount of time given to the mashing or 

 hydration fermentation. 



Thus we may briefly sum up the changes produced by 

 the statement that the infusion products of starch will be 

 more dextrinous, i.e., least altered according as we lessen 

 the time, the amount of water, and the growth of the 

 plumules in the malting process ; and on the other hand 

 'i infusion products will be richer in Glucose (dextrose), 

 1 therefore attenuate lower in the subsequent fermenta- 

 tion process, according as we increase the amount of 

 water, the time of infusion, and the growth of the plumule. 

 The variations in these directions introduced in the 

 mashing process in English breweries are within a narrow 

 range, and the products formed have a reducing action on 

 Fehling's liquid, varying from 50 per cent, to 55 per cent. 



j of the total hydration possible by the aid of mineral 

 acids. 

 The use of unmalted grain is prohibited in England, 



I whereas cane-sugar and Glucose (made by the action of 

 dilute acid on grain) are allowed. The variations in the 

 direction of dextrine-increase were until recently very 



1 limited, but on the other hand those in the direction of 

 alcohol-yielding sugars are without limit. 



g Messrs. O'Sullivan and Valentin, in a communication 

 the Society of Arts (March 17, 1876), have recently 

 jwn how the action of dilute sulphuric acid may be so 

 julated as to obtain O'Sullivan's dextrine-maltose reac- 

 tion already described. 



The hydration by the agency of very dilute sulphuric 

 id is carried on until the liquid has a rotatory power of 

 171°, indicating two parts of maltose (rotatory power 

 1 50"^) and one part of dextrine (rotatory power accord- 

 iug to O'SulUvan -f 213°), i.e., 



P 



2 X 150 J- 213 ^ + i-io 



3 



'I soon as the polariscope indicates O'Sullivan's reaction 

 be complete, the further hydration is stopped by the 



idilion of chalk. Should the mixture of dextrine and 

 iltose thus made prove to yield a stable and good- 



jeping beer, they will have contributed greatly to coun- 



ract the evil tendency of recent legislation by which 

 jL-er more and more alcoholic has been manufactured. 

 Having briefly examined the hydration of starch by 



albumenoid alterative ferments in the brewer's mash-tun, 

 we have now to consider the breaking up of the still 

 complex saccharine products of the reaction into bodies 

 of simpler structure, such as alcohol and carbonic acid, 

 which result from the fermentation process properly so 

 called. Though it is with alcoholic fermentation, with its 

 characteristic boiling or disengagement of carbonic acid 

 gas, that we have chiefly to do, at the same time other 

 products of the decomposition of saccharine bodies, such 

 as acetic, lactic, and butyric acids, must necessarily be 

 considered before v" can obtain a correct insight into the 

 phenomena which present themselves in the manufacture 

 of beer. 



Let us then follow the products formed by the hydra- 

 tion of starch already studied. 



The wort, as the brewer terms the liquid containing 

 the infusion products of the mash tun, is drawn off from 

 the insoluble matters of the malt, and is then boiled in 

 another vessel along with hops ; the amount of this valu- 

 able agent of preservation employed depending upon the 

 strength of the wort, the nature of the product desired, 

 and the length of time it has to be kept before being 

 consumed. 



By mere boiling, some of the albuminous bodies are 

 rendered insoluble, a further portion is precipitated by 

 the tannin of the hops, and the resulting liquid, being 

 thus deprived of some of the albuminous food materials, 

 is found to be less liable to subsequent destructive 

 changes. The hops at the same time yield a pleasant 

 bitter principle, and essential oils which play no slight 

 part in the preservation of the manufactured beer. Now, 

 unlike the juice of the grape, the infusion of malt is so 

 rich in albuminous matters, that every expedient is 

 adopted to diminish these aids to destruction ; hence the 

 process of boiling, the use of tannin, and the employment 

 in the infusion process of hard water containing salts of 

 lime. To its water Burton chiefly owes its reputation for 

 good ale. The boiled wort, when cooled, is placed in 

 fermenting vessels, and yeast is added. This addition of 

 yeast is almost universal ; at the same time it must be 

 noted that in the production of Faro and Lambick the 

 Belgian brewer adds no ferment ; a similar practice was 

 at one time rather common in England, and is even now 

 occasionally to be found in Wiltshire. In thus adding no 

 ferment, the brewer follows the invariable practice of the 

 wine-maker, who leaves the must or pressed juice to 

 spontaneous fermentation ; the wine-grower may reason- 

 ably reckon upon a definite decomposition of his must, 

 but the brewer who follows this method can foretell but 

 little of the result. We shall presently see why the wine- 

 grower's must and the brewer's wort comport themselves 

 so differently under apparently the same conditions. The 

 spontaneous fermentation of malt wort, even now so little 

 practised, is doomed to be altogether discontinued within 

 but a few years. 



The English brewer, having cooled his wort to a tem- 

 perature varying from 14° C. to 18° C, and having added 

 yeast, the fermentation commences, the heat, unless 

 checked, rapidly rises, and the yeast greatly increases in 

 quantity, the larger portion of which rises to the surface 

 of the liquid. Hence this is termed top or surface fer- 

 mentation, in order to distinguish it from the Bavarian 

 process, in which the yeast sinks to the bottom of the 



