Acids as Starch Converting Agents


The following paper was read and discussed  :-

Acids as Starch Converting Agents in Brewing

Up to the present time brewers have used nothing but the diastase of malt as a starch-converting agent.  The hydrolytic action of acids has only been employed in the manufacture of glucose, and to a certain extent in distillery work.  Although the transformation of starch by acids is, in its broadest sense, the same as that produced by diastase, there are such notable differences between the two processes that the question arises if these are not sufficiently great to indicate that an attempt to substitute acids for the diastase of malt in the manufacture of beer might be considered as at least dangerous.

We know that although hydrolysis of starch by diastase gives rise to the production of maltose, this sugar, if formed by the action of acids, undergoes inversion with the production of dextrose or d-glucose.  It may be further observed, without entering into details of such complex phenomena as those which characterise the degradation of starch, that the intermediary products between the starch and sugar do not seem to be the same by the action of the acid as those produced by the action of diastase.  Certain soluble carbohydrates besides sugar, produced by acids, which may be denoted as dextrins, are not acted upon by diastase and are unfermentable.

Several Belgian brewers have for about a year substituted hydrochloric acid for the malt originally employed in the conversion of raw grain.  This method of procedure was introduced by P. Callebaut.  It consists in liquefying maize grits in the presence of acid under a pressure of 37 lbs. per square inch until the product gives a violet tint with iodine, which corresponds to a small production of reducing substances.  The mass is than discharged into coppers, almost entirely neutralized by carbonate of soda, and afterwards run into the mash-tun, where the saccharification is continued with malt.  It not quite neutralised, in order to promote in the mash-tun the dissolution of a certain quantity of acid phosphates, which, as we know, exercise a considerable influence upon the rate of fermentation.  The brewer can therefore employ with the greatest facility as much as 70 per cont. of raw grain.

As an illustration, 1 will give you complete details of a brew as carried out in a Belgian brewery, brewing upon this method.

  1.  Conversion of the Maize Grains

The brewing commenced at 7 AM precisely.  7½ barrels of water and 17½ lbs of commercial hydrochloric acid were introduced into the converter.
     The converter may be made of iron or copper; the latter is, however, preferable, the copper always maintaining its value and not being attacked by the very dilute acid.
     The acid liquor is raised to boiling by the injection of steam, then 6 qtr. ground maize grits were gradually added.  At 7:26 AM the converter was charged, then closed down and put under pressure.  At 7:42 AM the pressure was 15 lb. per square inch.
     At 7.51 A.M. 30 lb. per square inch.
     At 8 A.M. 37 lbs. per square inch.
     At 8.18 A.M. the contents were discharged from the converter into the wort copper, and the whole neutralized with 10 lb. of carbonate of soda previously dissolved in 4½ gallons of water. The converter was empty by 8:24 A.M.

     2.    Saccharification

     At 8:29 AM commenced operations in the mash-tun, the capacity of which was 31 barrels.
     3 qtr. of malt, ground very fine, were mashed with water at 82o F.
     At 8:34 AM. the neutralised matter in the copper was discharged into the mash-tun, the heat of it being 197o F.  At the same time, water at 206o F. was introduced under the false bottom of the mash-tun.  The running in of the maize was finished at 8:46 AM and the tun filled by 8:47 AM.  The rakes, which had been working from the commencement, were then stopped.  The temperature of the mash was 154o F.  The mash was allowed to stand until 9:49 A.M., when the tap fixed half way up the tun was opened, and the wort flowed out almost clear at a heat of 148o F.  It gave no reaction with iodine and the density of the first runnings at 60o F was 30 lbs.
     The taps were shut at 10:40 AM and water at 156o F was introduced the false bottom for the second mash, the rakes meanwhile.  The tun was filled at 10:52 AM and the heat was 159o F.  At 11:15 AM the liquor was drawn off a 156o F by the lower tap; it was a little turbid at first but afterwards brilliant (density at 60o F 7*2 lbs)
     At noon the running off of the second mash was finished.  The third mash was made in the same way with water at 167o F.  At 12:12 PM, the tun was full, the temperature of the contents being 161o F.  It was allowed to stand for 10 minutes, and the third wort then run off.  All the worts were collected in the copper by 1:15 PM

3.  Hopping and Boiling

     85 lbs. of Alost hops were used, part added at the start, and the remainder 30 minutes before turning out.  The duration of the boil was four hours.  30½ barrels of wort at 16*5 lbs., and 30 barrels at 7*2 lbs., were obtained or a yield of 89*9 lb. per quarter.

4.   Samples Taken

     During the conversion of the maize the following samples were taken :-
No. 1 at the sample tap in converter, pressure 37 lbs., at 8 AM.
No. 2                                                                           at 8:07 AM
No. 3                                                                           at 8:11 AM
No. 4                                                                           at 8:16 AM
No. 5. Neutralised sample, taken when the converted grits were discharged into mash tun.
Nos. 1, 2, 3 gave with iodine a purple blue reaction; the others gave a violet reaction.
     Equal volumes of samples 1, 2, 3, and 4 were added, upon being drawn off the converter, to equal quantities of a concentrated solution of carbonate of soda, in each a manner as to neutralize them perfectly, and as quickly as possible.

     In samples 1, 2, 3, 4, 5 were determined :-
(a) Dry matter; (b) ash; (c) acidity expressed as HC1; (d) matter soluble in cold watcr; (e) matter soluble in hot water, after extraction by cold and rejection of the cold washing water; (f)insoluble matter after both washings; (g) glucose.

The matter is not homogenous which explains a few slight anomalies in the figures I am about to give.  These have been determined directly, and several of these determinations were effected upon different portions of the conversions.

Composition of Dry Matter
100 parts of grits, used in converter and supposed to be quite dry, contain :

The matters soluble in cold water contain :-
     (a) The acids; (b) a part of the mineral substances (we will suppose them to be entirely soluble, which will lessen the figures relating to the dcxtrins); (c) reducing sugars (as dextrose) ; (d) the difference consists principally of the dextrins with a little nitrogenous matter.
     The matters soluble in hot water, after thorough elimination of the part soluble in cold water, can be taken without appreciable error as soluble starch.
     The insoluble matter comprises that part of the grits not acted upon.

Composition of Dry Matter

An inspection of the figures in this table shows :-
     (1) That the major part of the dry extract of cooked grits is found to be dextrins.
     (2) That after the pressure in the converter attains 37 lbs., the proportion of the reducing bodies increases quicker than the solution of the remaining starch, the formation of glucose taking place especially at the expense of the dextrins and the soluble starch.

The beers obtained by the process I have just described show but an apparent feeble attenuation after the principal fermentation (55½ per cent.)  The feeble attenuation obtained prior to racking certainly arises from the cause that the wort was poor as regards nitrogenous matter.  The primary yeasts are incapable of pushing the attenuation to a degree sufficiently approaching their attenuation limit, leaving this to the care of the secondary yeasts less particular in their choice of nitrogenous food.  In spite of this, these beers keep very well, and the results are satisfactory enough, as for about twelve months several Belgian brewers have worked upon this method.

Such is the process I have seen worked in Belgium, and a description of it I thought would be interesting from the point of view that it constitutes one of the attempts that have been made to substitute the action of acids for that of malt in the brewery.


     The PRESIDENT, in inviting discussion, said the author had described a very interesting system, but he did not know whether it had been made use of in England.
     The AUTHOR said the method he had described was now largely in vogue in several Belgian breweries working on the top-fermentation system, but it had not yet been introduced into England.
     Mr. A. L. LEES asked if the fermentation was conducted on the same lines as in England, and what action had the particular class of wort on the yeast crops?  Was the yeast carried through consecutive brews and worked on the same lines from the same wort, and with what results?
     The AUTHOR replied that the process of fermentation he had referred to in the paper was in some ways similar to some of the English methods.  Worts produced in the manner he had described had no prejudicial effect on the yeast crop.  The yeast was used over and over again without change, and with excellent results.
     Mr. LEES said, with reference to the flavour of the beer, he should like to know if the author had carried out any experiments at Burton?
     The AUTHOR said he had made some experiments on a small scale, and had found that the resulting beer was trot readily distinguishable regarded flavor or other characteristics from the beer brewed on the ordinary lines.
     Mr. LEES said some years ago he had a similar experience, and he found that the great difficulty in dealing with products of the kind before them was the after-flavour, especially where lime was used as a neutralising agent.  The difficulty was to get the exact amount to neutralize the acid flavour and obtain an agreeable softness.
     The AUTHOR said it was well known that the use of large quantities of raw grain under the ordinary system of working had certainly a tendency to change the character of the beer.  As to the exact amount of carbonate of soda required to neutralise the acid that could easily be calculated.  Of course it must be remembered that the acidity was not completely neutralized, in order that the free hydrochloric acid remaining might in the mash-tun affect the solution of the insoluble phosphates.  These worts, being rich in acid phosphates, would ensure the fomentation being normal, and the yeast crop satisfactory.
     The PRESIDENT said it appeared that under this system up to 70, 80, or 90 per cent. of raw grain could be used.  The author could work up the raw grain treatment under pressure, with the addition of 10 or 20 per cent. of malt.  It was evident that the malt had some effect upon the converted raw grain.  He would like to know the nature of the action which caused by the addition of the malt where the raw grain had been treated under favourable conditions.  When the raw grain–the maize grit–had hen converted with acid into certain saccharine bodies, was the malt necessary, or was it added only for the purpose of giving a flavor?  Ten per cent. seemed a small quantity to give a flavour.  He therefore concluded that this quantity was required to act in some way upon the material which had been converted with acid.  It struck him that even the dilute acid might set up some chemical action in the copper vessel in which the raw grain was converted.  It was well known, he thought, in chemistry that hydrochloric acid, under a pressure of 40 lbs. to the square inch, would have the effect of bringing about some action on the copper.  The hydrochloric acid acting on the copper would produce chloride of copper, which would be very unhealthy; but it might be found in actual practice that the amount was so small as to not produce any injury.
     The AUTHOR said the 30 per cent. of malt used in the mash-tun acted upon the un-converted starch, which was afterwards completely saccharified.  The malt was required for the saccharification under the influence of the diastase during the mash-tun operation.  A certain amount of malt was absolutely necessary in this process, otherwise it would be impossible to effect the running off of the wort from the mash.  The amount of acid in this process was so small that no appreciable chemical action could take place on the metal employed in the construction of the converter.
     The PRESIDENT said that what he wished to know was whether the action of the acid on the starch altered it in such a way and converted it as completely as if it had been converted by the addition of malt.
     The AUTHOR replied that the action of the acid under pressure rendered the starch soluble in such a manner that when it came in contact with the cold water malt extract it was very soon saccharified.
     Mr. E. F. HYDE asked if the author had tried to carry out the conversion of the grits without pressure.  It would take a longer time, he had no doubt, with 2 per cent. of hydrochloric acid at a temperature of 213 or 216o F., perhaps three or four hours longer, to arrive at the same result.  After the conversion was complete, and it was running into the copper, was the neutralisation completed or not?
     The AUTHOR said in this process it was required to carry out the conversion of the grits under pressure. After the conversion was completed the mass was neutralized, but not completely, as distinctly said in the paper.  The acidity was stated in the percentage of dry matter, and expressed as HCl.
     Mr. MUNRO inquired how long the beer had to be kept before being consumed.
     The AUTHOR replied that it was treated in a similar manner to that in vogue in this country. The experiments he had referred to had been conducted with Belgian yeast.  If English yeast had been employed, the attenuation would have been much lower.
     Mr. C. H. HILL proposed a vote of thanks to Mr. N. van Laer for his interesting paper.
     Mr. LEES seconded the motion, which was carried unanimously.
     Mr. NORBERT van LAER having acknowledged the vote of thanks, the proceedings terminated.

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