MEETING HELD at the ROYAL VICTORIA HOTEL, MANCHESTER, on Thursday, April 7th, 1904.
Mr. Jas. G. Groves, M.P., in the Chair.
The following paper was road and discussed: —
The Chilling and Filtering of Top-Fermentation Beers. Part III.
By N. Van Laer.
When I had the honour of reading my first paper on this subject before this Institute in October, 1900, in the discussion which followed, I was asked to continue the subject and contribute a paper on the carbonating of beer. It was my intention to comply with your request, but this communication being a continuation of a previous paper, I will ask you to allow me to enter into ono or two outside details not directly related to carbonating, in the ordinary sense of the word.
During the month of July 1901, I had the pleasure of studying, at a large brewery at Berlin, an American process (“Wittemann Beer re-saturating system), of mechanically saturating beer with the natural aromatic carbonic acid gas given off from the fermentation. I must here point out that this method should not be confused with the carbonating of beer by liquefied CO2 derived from fermentation. From what I gathered, this process has made considerable head-way in the United States, where it has been in operation for several years. According to the reports of those brewers working by this system, I may say that the results have proved very successful. A description of the system may perhaps be of interest to our progressive brewers. We know that carbonic acid gas liquefies at various pressures ranging from 520 lbs. at. 32° F., up to 1,000 lbs. at 80° F. In order to reach the liquefying point, the gas usually passes through two or more different compressors and through as many condensers. The compression temperature is therefore very high, and as the compressors require a great deal of lubrication at such high pressures and temperatures, contamination of the gas is extremely difficult to avoid. Therefore, liquefied CO2 obtained from fermentation often contains impurities which are very detrimental to the flavour and properties of beer. The liquefied fermentation gas, if collected free from air, consists of about 99 per cent, of carbonic acid gas, 0·5 per cent, of ethers, 0·25 per cent, of alcohol vapours, and 0·25 per cent, of moisture.
These figures naturally vary very much according to the method of collecting and purifying the CO2 For example, I have known CO2 gas derived from the fermentation of beer, as supplied to bottlers, which contained at the top of the gas cylinder under the valve, as much as 13 per cent, of air and other gases, while at the end of the cylinder, when nearly empty, 0·5 per cent, of air was still present. This amount of air is exceptionally high, and carbonic acid gas containing so largo a percentage of air should be rejected for the carbonating of beer. Practical experience has demonstrated that fermentation gas does not change in composition or flavour when compressed at a pressure of 200—240 lbs., and refrigerated within 24 hours to a temperature of about 32° F.
I will now give a brief outline of the working of this system as I have seen it in practical operation. By following the accompanying illustration, the manipulations will be easily understood. A few practical remarks will be of assistance in grasping the various details connected with the working of this system.
It is recommended to collect the fermentation gas from a well-hopped beer such as pale ale, so that the gas collected will contain a certain proportion of aromatic vapours. The type of beer is of considerable importance with regard to the aromatic and volatile compounds given off. Some of these can he easily detected in comparing the gases from different sorts of beer. I have compared the gas collected from a Munich type of beer with one from a Pilsener beer. The difference in flavour and smell was indeed very marked, and one could at once distinguish one gas from the other by the aroma and appreciable character of the beer treated by the two kinds of gas. It is estimated that the average yield of gas produced from fermentation is about 13½ barrels of gas at atmospheric pressure, for every one barrel of beer fermented. Taking as an example a 50-barrel fermenting vessel, the beer in a vessel of this capacity would yield sufficient gas to carbonate 500 barrels of beer at 10 lbs. pressure per barrel. Consequently, every eighth brewing, allowing for waste, will produce an ample supply of gas to carbonate seven other brewings of the same capacity. Hence an eighth part of a brew, or in other words, every eighth brewing is transferred (after about 16 hours from the time of pitching in the ordinary open fermenting vessel) into a special covered gas collecting and fermenting vessel or vat, or if preferred, the ordinary fermenting vessel may be covered for the purpose of collecting the gas. The fermenting vessel or vat in which the gas is being collected, is connected to a main which leads to the gas compressor and provided with a safety valve. The gas given off passes from the closed fermenting vessel to the gas compressor, and from thence through the purifier to the gas-storage cylinders, which are in a cold store. A slight pressure ranging from 3—6 lbs. is kept on the collecting vessel. Under this small pressure, the fermentation and attenuation aro not checked, while the temperature may be regulated by means of attemperators.
When the necessary amount of gas has been collected, the fermentation may be finished in the closed fermenting, or if preferred, the beer may be returned to the open fermenting vessel if the fermentation is carried out on the skimming system, or if working on the union system, the fermentation may be completed in those in the usual way. Once the fermentation is over, the beer is racked through an instantaneous chiller to the cold storage vat, where it is kept at about 32o F. for a period varying from 5 days upwards. The period of chilling is left to the judgment of the brewer and varies according to the type of beer under treatment. Before describing the saturating process, I will say a few words concerning the gas compressor and storage tanks. The compressor is of special construction, fitted with solid bronze cylinder, water-jacketed, in which the gas is compressed at about 200 lbs. together with a certain amount of cold water which is forced back from the receiver. The latter is placed in a refrigerated cellar and serves as a gas washer as well. The cold water returns to the compressor at once, lubricates it, instantaneously absorbs the heat, which is naturally created by the compression of the gas, prevents it from over-heating, and finally washes the gas free from a certain amount of acidity. The water passes through the body of compressed gas within the receiver in a constant fine spray which frees it from impurities. The purified gas, on leaving the compressor, is forced into the gas-storage tanks. Pressure is raised in the latter, one after the other up to about 240 lbs. It is estimated that a storage tank of 15 barrels liquid capacity will hold, at 240 lbs. pressure, 240 barrels of gas at ordinary pressure. It is claimed that gas compressed on one day may be used the next. With tanks sufficient to hold the gas required for 2- or 3-days’ use, gas need be collected but once a week. I will now rapidly refer to the carbonating of beer by this system. As the illustration shows, beer is taken from a vat by a pressure regulating pump. It may be flat stock beer, or beer racked directly off the yeast into chip casks and allowed to get into an after-fermentation, and by its own pressure cause the settling of the yeast, resinous and other matters. It is advisable to force the beer under a small pressure of from 3—6 lbs. to the regulating pump. To prevent the rising of sediment, the pump of a duplex piston pattern working with 20—25 lbs. pressure (air or reduced steam, whichever is available) raises the beer pressure from 3—5 lbs. above the intended saturating pressure and automatically maintains it, feeding into the saturator or carbonator through a level-regulating valve, governed by an overflow receiver hanging from a balancing arm and connected with its valve stem. Gas is fed under uniform pressure into the carbonator through a pressure-reducing valve from a food pipe connected to the various gas-storage tanks. Thus, hundreds of barrels of beer can be carbonated without the necessity of even connecting another gas tank. The apparatus once “set,” is automatic and requires no further attention. By the process, the beer can be heavily charged with carbonic acid gas, at pressures ranging from 15—50 lbs., provided a counter-pressure racker is used. The carbonated beer flows from the carbonator under an evenly maintained gas pressure, in a quiet stream through a filter to the nicker or filler, providing a suitable counter pressure of gas and air is maintained. The cost of collecting and compressing gas by this system is insignificant, a 6-h.p. compressor being capable of compressing sufficient gas to saturate 25 barrels of beer per hour, making a total of 600 barrels every 24 hours. Compressors may be obtained, either steam or belt-driven, of 300, 600 and 1,000—2,000 barrels daily capacity. It may be interesting to give a typical example here of the working of this process on a large scale as described by a practical brewer of long-standing experience in this direction. In a very interesting communication* on this subject by Mr. Frank Bechtold, the author describes this system in detail, the following being an abstract of his remarks: — “In order to carbonate 1,000 barrels of beer, about 120 barrels of wort are used which has been pitched in the same manner as the other beer, and is brought into the gas-collecting tank. I use a storage vat with a capacity of 160 barrels so that there will be room for 40 barrels of gas to collect. The vat must be air-tight. At first it is allowed to remain open 5—6 hours, in order to enable the carbonic acid to force out all air. In order to be sure, a test is made in the following manner.”
* “Letters on Brewing,” Hantke’s Brewers’ School and Laboratories, Milwaukee, U.8.A., January 1903
“Fill a bottle under water, of the gas and a little caustic potash or caustic soda. The carbonic acid gas is completely absorbed so that a vacuum is formed in the bottle and the bottle is filled with water. If the bottle is completely filled with water, it is safe to assume that the gas is free from air, otherwise a complete vacuum is not obtained. If the gas has been found to be pure it is carried by means of a compressor to the gas tank and placed under a pressure of 240 lbs. The gas first passes through a tank of cold water whereby it is cleaned and moistened. The water furnishes cold water to the cylinders of the compressors so that the gas is compressed in a cold state and, therefore, will suffer no damage. For this reason, it gives the beer a fresh, pure, and aromatic taste. We carbonate 40 barrels per hour, but the system is capable of carbonating 75 barrels per hour.”
The advantages of this system over the old methods of carbonating are indeed numerous, and I will here enumerate only a few: —
1. The beer is saturated with the gas given off from the fermentation, and from a beer specially selected for this purpose, i.e., a beer well hopped and possessing high aromatic properties.
2. The delicate volatile aroma of the essential oil of the hops will impart to the beer a hopped flavouring which will dispense with dry hopping.
3. Krausening and priming are no longer required.
4. The cost of collecting the gas is infinitesimal and should not be confused with the ordinary method of collecting and compressing the CO2 of fermentation industries.
5. The storage is very much shorter without impairing the character of the beer.
6. There being a complete absence of sediment in the cask or bottle, the beer draws brilliant to the last drop, therefore saving finings, bottoms, waste, or returns.
7. The manipulations to which the beer is submitted, being rapid and automatic, a great deal of labour and time is saved.
8. It ensures absolute uniformity in the character of the beer, consequently maintaining the reputation of a brewery for the excellence of its beers.
Such is a résumé of this very interesting system; it was my wish to acquaint you with. I trust that at no distant date, this system may make the same progress in England, and prove as successful, as it has done in the United States. Before concluding, may I again call your attention to the important question of hopping the beer in order to obtain the full benefit of the aroma after filtration. In my first paper (J. Fed. Inst. Brewing, 1900, 6, 439—453) I have already referred to the deficiency of hop flavour in beer treated by the chilling and filtering process. During the last few years, I have carefully gone into this trouble of loss of aroma, and have come to the conclusion that the most satisfactory manner in which to overcome the difficulty is to adopt the Continental method of passing the boiling wort from the coppers on to dry hops in the hop-back.
For this, the hops which are of the finest quality, are broken up and placed in the hop-hack while the hops from the boiling are collected in the special perforated tray. The boiling wort is run on to the hops and left in contact with them prior to being pumped to the coolers. I have had the opportunity of tasting various kinds of beer of different gravities which have been treated at the rate of 4 oz. of dry hops to the barrel, and without any further hopping-down in the cask. On examining these beers, and comparing them with others, hopped at racking, at the rate of 6—8 oz. per barrel, and on these being sub mitted to similar conditions of chilling and filtering, I found that those which had been treated in the hop-back were superior in respect to the aromatic and keeping properties to those beers hopped in the ordinary way. I may add that the hops from the hop-back (i.e., when a perforated tray is used) are, as a rule, returned to the coppers and boiled with the others. It is hardly necessary to point out that besides the problem of hopping, there are other very important factors to be considered in the production of suitable beers for the purpose of chilling and carbonating. The selection and blending of materials, the mashing operations, the fermentation process, the attenuation and racking require special attention over the ordinary methods of brewing. To enter into the above details would lead me too far and somewhat out of the object of this paper.
Until recent years, the prevailing opinion amongst brewers was that, the carbonating was only applicable to light gravity beers.
Since the introduction of the chilling and filtering process, the carbonating has gradually been applied to nearly every kind of beer for bottling, and doubtless the results have proved very satisfactory. This may, to a certain extent, be attributed to the immense progress made in the perfection of the mechanical details connected with the chilling apparatus, carbonators, filters, and counter-pressure fillers. The makers of these machines have lost no time in perfecting everything that was required to give complete satisfaction to brewers and bottlers. Having on various occasions made tours of inspection to the leading Continental breweries, I have had the opportunity of following the improvements made in connection with cooling appliances, carbonators, and all other requisites pertaining to this industry. Although I do not wish to criticise any particular construction of machine, I must, nevertheless say a word or two in praise of the English and American makers of these machines, for the high standard of perfection to which, of late, they have brought the mechanical part of this system.
I believe that the British public are gradually accustoming themselves to the taste of chilled carbonated beers, and I do not see why, in the near future, the demand for this class of beer should not become universal in Great Britain.
Discussion.
The Chairman having invited discussion,
Mr. W. M. Richards said that a friend of his had a Karl Kiefer beer filter, which he had seen working, and from what he had gathered, it was giving satisfaction. He would like Mr. Van Laer to give them a description of the filter they had been shown on the screen and inform them who were the makers of it
Mr. Van Laer, in reply, said that he had no experience of the Kiefer filter, although he had been invited to see it working. He had seen the filter in detail and also examined and tasted beers filtered with it. This filter had a large filtering area which he believed was of 18,000 square inches with a filtering layer of 1 inch in thickness to each plate. The pulp was compressed in a packing machine by means of hydraulic pressure. With regard to the description of the filter they had seen illustrated, it was based on the multiple plate system, somewhat similar to that described in a paper by Heron and Eiley (J. Fed. Inst. Brewing, 1902, 8, 307). The Wittemann filter was simple, strong, and effective. It could be used with more or less plates as increasing capacity might require. The plates were inter changeable, and it was not imperative to place them in rotation by numbers after filter pulp was pressed into them. All parts were easy of access and open; they were extremely easy to clean, no bending over being necessary, or difficulty in handling the plates in the drum or tank. The frame was of cast steel; the plates and contact parts of heavy bronze metal fire-tinned. The tightening of the plates was effected by a screw wheel and a ratchet clutch. The inlet at the bottom was furnished with a by-pass, and both inlet and outlet had sight glasses. Air could not be mixed with the beer, as it was driven out as the beer entered from below. The apparatus was convenient to move to any part of the cellars.
Dr. Ellis Hyde asked if the author would explain how it was, beers of high gravity could be chilled and carbonated, while such beers could not be carbonated when there was no chilling employed.
Mr. Van Laer said that at the low temperature the beer was submitted to in the chilling process the gas was rapidly absorbed. It was owing to the cold state of the beer that high gravity beers could so easily be carbonated, and with a high percentage of carbonic acid without causing any fobbing during the filling process. Unless the beers were chilled and carbonated at low temperatures, about 32o F., it was practically impossible to saturate these sufficiently to obtain the sparkling characteristic of bottled beer.
Dr. Ellis Hyde further inquired if the author had analysed the beers before and after chilling, in order to ascertain what effect the chilling had upon them.
Mr. Van Laer said that some years ago he had carried out n number of analyses in order to ascertain the effects of chilling and filtering on the composition of the beer. He had already referred to this in his first paper on this subject (J. Fed. Inst. Brewing, 1900, 6, 447, 448).
Mr. H. J. Marriott asked whether the enclosing of the fermenting vessel long enough to collect the necessary carbonic acid gas, had any effect on the fermentation by the exclusion of air?
Mr. Van Laer said that the vessel for collecting the gas was only closed during the period that the gas was given off most abundantly, and the fermenting vessel was opened again when the necessary amount of gas had been collected. The beer was then exposed to the air and the fermentation finished in the usual way. The beer fermented under cover was not affected by this operation, and, of course, he would point out that this beer was mixed with the bulk of the remainder of the beer fermented in the open.
Mr. Marriott further inquired whether the carbonic acid was more economical, inasmuch as it contained a percentage of hop aroma, and did it by this means do away with, to a certain extent, the loss of hop flavour so frequent in chilled and filtered beers?
Mr. Van Laer said that the object of this system was to restore to the beer the natural carbonic acid gas, the properties of which had not been destroyed by high compression, and in a pure state with its volatile aromatic compounds. Therefore, in carbonating beer by this system, the carbonic acid gas introduced into the beer contained a certain amount of hop aroma which was well maintained and absorbed by the beer, making up for the deficiency so often experienced with regard to aroma in chilled and filtered beers.
The Chairman asked if Mr. Van Laer would give them some particulars re the construction of the beer cooler, which they had seen illustrated? Also, what was the cooling capacity of same, expressed in barrels of beer chilled per hour? Did Mr. Van Laer recommend carbonating before or after filtration?
Mr. Van Laer said that with regard to the construction of the beer cooler, he would point out that some of the first coolers introduced to brewers either lacked in capacity or were difficult to clean, or caused freezing back to the refrigerating machine if direct expansion was chosen. The advantage of causing counter currents of the liquid need not be dwelt upon, it was well known. Not so well recognised was the necessity to also provide the necessary length of channels without going to extremes. Naturally the less the contact with metal surfaces was needed the better for the beer. Briefly stated, the inner beer channel of the chiller ho was referring to was formed of seamless steel tubing, heavy enough to stand any possible pressure, yet light enough to act as a good conductor of heat. Those tubes were carefully and doubly fire-tinned inside and outside, so as to be impervious to beer, brine, and ammonia. The tubes, while round at both ends, were fluted into the shape of a rounded cross between ends, for the double purpose of exposing the flow of beer to the largest possible cooling surface and of changing its current, so as not to leave any of the moving body of beer without the proper contact with the cooling surface. The tubes rested in double stuffing boxes at both ends, so that they could be drawn out should they, in time, need re-tinning. It might be interesting to state that tinned steel tubes in coolers, in use for over 4 years, were still in perfect condition. The inner or beer tubes wore connected at both ends by fire-tinned bronze bends, which had thumb bolts, making it easy to detach them when the beer tubes were to be inspected or brushed out. The outer tubes were of extra heavy pipe, with secure joints, screwed and soldered into steel headers all galvanized. Both in- and out-lots were provided with tinned bronze Ts, with heavy, detachable, round way cocks on one outlet, and capped hose bungs on the other (both being interchangeable), making the cleaning of all parts convenient. With regard to the cooling capacity, he said that it would vary with different temperatures. It also differed with brine and ammonia circulation, the former usually proving more effective. To give them some idea of the same, he stated that the capacity, working with brine, varied from 30—90 barrels and upwards per hour. Concerning the important question of carbonating, before or after filtration, as far as his own observations went, very good results were obtained by carbonating after filtration; that was as long as the beer remained in a cold state. Naturally, this was a matter which largely depended on various factors and according to disposition of the plant.
Mr. Peer Groves asked whether the filter referred to in the discussion could be applied for filtering small quantities of beer? Would an ordinary oak beer cask filled by this process retain the gas if kept at a low temperature?
Mr. Van Laer replied that the filter was admirably adapted for that purpose. When dealing with small quantities of beer, all that was. required was to place the right number of filtering plates according to the amount of beer to be filtered. This was of great importance as very little beer was wasted by the absorption of filtering medium. Moreover, the beer was not exposed to large metallic surfaces, so detrimental in some filters. With regard to filling ordinary oak beer casks with beer produced by tins system, he said that these would require careful selecting and, if strong enough to stand the pressure of carbonic acid gas and maintained at a low temperature, he did not see why they should not be used for this purpose.
The Chairman proposed a hearty vote of thanks to Mr. Van Laer for his instructive paper, which like the discussion following it had been, he said, very interesting. This was seconded by Mr. Peek Groves and carried unanimously.
Mr. Van Laer suitably acknowledged the compliment and the meeting then terminated.
Crescent City Brew Talk 