STUDIES ON GUSHING III
CONTRIBUTION TO THE PROBLEM OF GUSHING
By A. Ferdinandus, J. Gombert and H. E. Jansen
(Heineken’s Brotiwerijen Nederland N.V., Rotterdam)
Received 6th February. 1962
Hydrogen gas, formed in bottled beer during the action of beer on the aluminium spot of the crown cork, may promote gushing, if the beer initially has a high content of dissolved nitrogen. If under otherwise similar conditions, however, this initial nitrogen content is low, no gushing is observed. Thus the presence in beer of relatively large amounts of dissolved nitrogen and hydrogen can be considered as a potential cause of gushing. As high contents of dissolved nitrogen in beer may be due to an insufficient after-fermentation, this accordingly may contribute to gushing.
Introduction
In the last 25 years, many papers have been published on gushing. Instead of giving details of this rather extensive literature, some publications will be reported here in brief. Helm & Richardt4 and Gray & Stone2 gave ample evidence of the influence of different factors, amongst which were mentioned the presence of heavy metal ions in the beer, pasteurizing, shaking and cooling of the bottle, a horizontal position of the bottle and the barley variety. Brenner1 found as an essential factor the presence of calcium oxalate crystals, Helm5 that of sodium nitrate, Kenigsberg & Stone6 and Gray & Stone3 respectively that of nickel and other heavy metal ions. Nakamura8 attributed gushing to a strong proteolytic action, and Rudin & Hudson9 proved that metal complexes of isohumulone compounds could induce gushing (see also Luykx7), and that this could be compensated by the addition of EDTA.
The foregoing shows that most research on gushing was and still is focussed on the determination of gushing factors in beer. The presence in barley and in malt of compounds which may possibly give rise to gushing has been mentioned, but particulars of these compounds have never been given. In general, gushing is attributed to nuclei, to solids as well as to small gas bubbles of foreign gases (non-CO2), which will liberate carbonic acid. These foreign gases mainly consist of nitrogen and hydrogen, the latter being formed in the bottle by the action of beer on the aluminium spot in the crown cork (see Sörensen10).
Experimental
As we had some indication that a high foreign gas content promotes gushing, an examination was carried out on the relation between gushing and amounts of gas dissolved in beer. In order to do this, beer with a rather poor attenuation in storage, and consequently with a high initial content of nitrogen, was bottled and submitted to overseas transport of some weeks. The crown corks used were of the normal type with composite cork, part of them with aluminium and the other part with PVC spots. Bottles were packed in the ordinary way: horizontal in wooden cases and vertical in cardboard boxes. During the whole transport they were kept in these positions.
After a period of 8-12 weeks the bottles were returned and were kept for some days in a standing position at room temperature, after which they were examined for gushing and for gas contents in the beer and in the head space of the bottle. The rate of gushing was expressed as (a) slight gushing, (b) moderate, and (c) heavy gushing, corresponding to, respectively, (a) head space filled up with foam, (b) up to 25 ml. of the beer flowing out of a 300-ml. bottle (50 ml. out of a 660-ml. bottle) and (c) more than 26 ml. overflowing from a 300-ml. bottle (more than 50 ml. from a 660-ml. bottle). The gas contents were determined by gas chromatography by the Analytical Institute T.N.O., Delft. Results are collected in Table I.
In a second series of similar experiments, part of the same beer in storage was washed with carbonic acid in order to reduce the amount of dissolved foreign gas. After bottling, using crown corks with aluminium spots, the bottles were packed in cardboard boxes and were submitted to further transport on a coaster, this time for 4 weeks only. During this transport, some of the boxes were placed normally, i.e., with the bottles in a standing position, while others were placed with the bottles in a horizontal position. The washing procedure with carbonic acid (0-5 kg. CO2 per hl. per 24 hr.) resulted in a reduction of foreign gases from 1-3 ml. to 0-2–0-3 ml. per 300 ml. of beer, this latter content.
After transport, the bottles were examined in the same way as before. The results were in full agreement with those of the first experiments, and are given in Table II.
Discussion
As no crystals of calcium oxalate were present in the beer, while the amount of iron and copper was no more than, respectively, 0-1 and 0-05 p.p.m., the gushing could not have been caused by these factors. On the contrary, there was no doubt that:
(a) gushing only took place in bottles with an initial high content of nitrogen and with high contents of dissolved hydrogen in the beer;
(b) high contents of hydrogen were only found in bottles which had crown corks with aluminium spots, and which had been submitted to trans port in a horizontal position; and
(c) negligible amounts of hydrogen were found in bottles which had been transported in a standing position and in all bottles, whether horizontal or standing, closed with crown corks with PVC spots.
From these results, it follows that with this beer gushing took only place in bottles with a considerable content of dissolved nitrogen and also of dissolved hydrogen. Apparently a combined action of both foreign gases induced the gushing. The carbonic acid content of the beer had only a very slight influence, and it certainly was not a deciding factor.
Formation of hydrogen was only observed in bottles packed and transported in a horizontal position, as only thus the beer was in contact with the aluminium. No gushing whatever was found in bottles transported in a standing position.
The mechanism of gushing when the bottle is opened may possibly be described as follows: Presumably by reduction of the partial hydrogen pressure in the head space to about zero the hydrogen escapes at once, forming microscopically small bubbles that act as nuclei for the liberation of nitrogen bubbles and these in their turn liberate the carbonic acid. As the bottles of beer washed with carbonic acid and with, in consequence, low dissolved nitrogen contents showed hardly any gushing at all, removal of initially dissolved nitrogen may prevent the hydrogen from provoking gushing.
In conclusion it may be said that, in this particular case of gushing, it has been established that the combined presence of dissolved nitrogen and hydrogen in the beer is the main cause for the gushing. The nitrogen originates from a poor attenuation in storage (sluggish after-fermentation), and the hydrogen from the action of beer on the aluminium spot in the crown cork in bottles stored in a horizontal position.
Acknowledgement.—We should like to thank Mr. H. Compaan and Mr. J. H. L. Zwiers from the Analytical Institute T.N.O., Delft, for assistance in carrying out the gas analyses.
References
1. Brenner, M. W., Proc. A.M. Amer. Soc. Brew.Chem., 1957, 5.
2. Gray, P. P., & Stone, I., Wallerstein Lab. Commun.. 1049. 12, 311.
3. Gray, P. P., & Stone, I., Wallerstein Lab. Commun., 1956, 19, 345.
4. Helm, E., & Richardt, O. C, Woch. Brau..1938, 55, 89.
5. Helm, E., Wallerstein Lab. Commun., 1952, 15, 184.
6. Kcnigsberg. M., & Stone, I., Walterstein Lab. Commun., 1955, 18, 285.
7. Luykx, J. M. M., this Journal, 1960, 399.
8. Nakamura, H., this Journal, 1954, 420.
9. Rudin, A. D., & Hudson, J. R., this Journal, 1958. 317.
10. Sörensen, J. A., Proc. Eur. Brew. Conv., Rome, 1959, 220.
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