THE MNEGAR INDUSTRY. 



Bv C. AIXSWOKTH MITCHELL. B.A. (Oxoni. F.LC. 



Notwithstanding the fact that the manufacture to three hours, the whole of the starch in the grain 



of vinegar is one of the oldest industries in this has been converted into sugar b}- the enzyme, 



country, and that in London alone there is an output diastase, present in the germ of the malt, 



of several million gallons a vear, it is surprising how When this conversion is complete the icorf, as the 



little is know n In- the outside world of the way in infusion is now termed, is drawn off, and, without 



which it is made. being boiled with hops, as in the case of beer, is 



This is largely the result of the policy of secrecv transferred to a fermenting tun, and treated with a 



with which each firm of vinegar - makers 

 jealousK' guarded its methods during the 

 last century : although, as thev were work- 

 ing upon practically identical lines. the\' had 

 little to conceal from one another. 



To such a pitch was this craze for secrecy 

 carried that some of the firms made use of 

 thermometers with marks upon them instead 

 of a scale, while others went e\en further, 

 and deceived their workmen bv the use of 

 thermometers in which the scales were of 

 set purpose graduated incorrecth". 





suitable \'east. 



In some \inegar works the wort is 

 obtained hv means of the conversion pro- 

 cess, instead of by mashing. In this process 

 the grain, usually rice or maize, without 

 malt, is treated with dilute mineral acid, 

 such as sulphuric acid, in a closed vessel 

 termed the converter. Under suitable con- 

 ditions the acid hydroh'ses the starch in a 

 manner analogous to that of the diastase of 

 malt, and produces a saccharine solution, 

 which, after neutralisation of the residual 



Figure 1. 

 In ail the British factories, which in the B. Kiitziiigiaiiuiu. acid with calcium carbonate and separation 

 year 1840 numbered forty-eight, the methods 



(Hansen). 



Figure 2. 



B. accti. 

 (Hansen.) 



of working had been handed down within 

 the works themselves, and few attempts 

 were made to reduce to a minimum the 

 chemical and mechanical losses inevitable ^ 

 during the manufacture. ^ 



During the last quarter of a century, 

 however, there has been a great improve- 

 ment in this direction, and many of the 

 factories now have up-to-date apparatus 

 and are under scientific direction, though 

 numerous examples of the primitive works, 

 universal fifty vears ago. still sur\ive. 



There has been little alteration in the 

 general principles of manufacture in an\- 

 of the works, the process still 

 following the three stages of pre- 

 paring a saccharine infusion of a 

 cereal, of fermenting the sugar in 

 this into alcohol, and of trans- 

 forming the alcohol into acetic acid 

 by the action of bacteria. 



Although wine vinegar is made to ^3^j__- s.o=c=t3- 

 a small extent in this country-, the o=cOc^ooO=>- ^'^=..s§^-==Cj 

 product chieflv sold is derived from 

 malt, or from a mixture of malt 

 with grain or sugar, and would 

 therefore be more correctly described 

 by the now obsolete term alegar. 



The first stage of its manufacture 

 is very similar to the mashing 

 process in a brewer\". The malt, or 





of the resulting insoluble calcium sulphate, 

 is readv for fermentation. 



Bv whichever method obtained, the w cirt 

 is now pitched w ith yeast, and is aerated 

 and kept at the best temperature to 

 convert as much as possible of the sugar 

 into alcohol. Upon the successful 

 working of this stage of the process 

 ^ largely depends the subsequent strength 

 of the vinegar, since all saccharine 

 matter i including dextrins) which has 

 escaped the action of the yeast, will 

 also remain unaffected by the acetic 

 bacteria. The fermented wort (now 

 termed ^j/e), which usually contains about 

 six or seven per cent, of alcohol, is 



-'O.-. 



;7c.JS??o:,^~^^^ 



now ready for the third stage — the 

 conversion of this alcohol into acetic 

 acid. This is brought about by the 

 action of specific bacteria, termed 

 acetic bacteria, which convey oxy- 

 sjen from the air to the alcohol, and 

 transform it into acetic acid. The 

 reaction that takes place in the 

 process is usually represented by 

 the formula — 



Figure 3. 



B. pastoriaimin. 

 (Hansen). 



C.,H,0 + O., 

 .\lcohol Oxygen 



CoH.O, + HoO 

 Acetic Acid Water 



Species of Acetic Bacteria multiplied 

 by 1000. 



though, in practice, many other com- 

 pounds are formed, in addition to 

 aldeh\de. w hich is probably invariabh" 

 mixture of malt and grain, is first crushed between produced as an intermediate stage in the oxidation- 

 rollers and heated in a mash-tun with water at a C.,HgO -f- O = C.jH^O + HoO 

 gradually increasing temperature, until, after two Alcohol Oxygen .\ldehyde Water 



219 



