the number to be used is large, and larger flasks would take up too much room. It is obvious that the power of preventing the growth of many organisms which wort and beer possess in virtue of the constituents derived from hops, and acid, etc., fails if too great a quantity of the water to be analysed is added, Holm has determined exactly the quantity of water which can be added to lager beer wort (about 14 per cent. Balling) before this happens. According to this author 15 c.c. of wort can be treated with c.c. of water, and 15 c.c. of lager beer with c.c. of water, before the resisting power fails. In many cases it would be an error to take so much water, since it may contain so many germs that the inoculation would give rise to too many growths. The water sample should on this account be diluted with a certain quantity of sterile water (or wort) or it may be added in smaller quantity to each flask. It is impossible to give a definite rule for this. In each case it is advisable to make a preliminary test in order to determine approximately the number of germs. A reliable result is usually obtained when one drop of the water is placed in each of 100 flasks with wort; these flasks are then set away at 25° C. The infecting of beer flasks can be dispensed with since Holm's investigations have shown that in his analyses organisms never appeared which were only capable of development in beer. Any growth which developed in the beer flasks was derived from such species as might easily grow in wort. In sowing a drop in each of 100 Freudenreich flasks containing wort, 5 c.c. of water in all are used, and in most cases this gives rise to not more than one growth in one flask. If flasks inoculated in this way have stood for one week at 25° C. and during this time no development has taken place, then there was, in the water sowed, no germ capable of development under the conditions of working. If such growths are present in some of the flasks, the contents of the latter are investigated macroscopically and microscopically, the number of growths noted and the quantity per 1 c.c. of the water calculated. It is of some moment in practical evaluation of the water to take note of the time after sowing at which development, especially of bacteria, takes place in the wort. For it is obvious that when they develop only after four or five days they must have been so feeble as to be capable of development with great difficulty or not at all under practical conditions. In the laboratory, conditions are far more favourable for development than in practice, since the rivalry with the yeast (and the low temperature) is wanting. The result of a water analysis will therefore always be such that rather more germs are found than would have reached development under practical conditions in spite of the attempt to copy these conditions as far as possible. Wichmann lays special stress on the importance, in evaluating the water, of noting the time when the "destruction" of the liquid under test takes place. He proceeds by adding to each of four flasks charged with 10 c.c. of wort, 1 c.c., c.c., c.c., and c.c. respectively of the water to be analysed. These four flasks are numbered 1, 2, 3 and 4. The destructive power of a water is taken as equal to 100, if all four flasks exhibit development after the lapse of a day; this number is got by multiplying the numbers of the flasks by certain factors and adding the four products. If development takes place in the flasks after one day this factor is 10, after two days 8, after three days 6, after four days 4, and after five days 2. Thus if all four flasks are turbid after twenty-four hours, the destructive power is: 10 × 1 + 10 × 2 + 10 × 3 + 10 × 4 100. If = = flask No. 1 shows development after two days, No. 2 after three, No. 3 after four, and No. 4 after five days, the destructive power is 1 × 8+ 2 × 6 + 3 × 4 + 4 × 2 40. From this it may be seen that Wichmann adds more water to the wort than Hansen and Holm in their analyses found to be advisable. 1 Schwackhöfer's Standard of Fitness of a Brewery Water. Schwackhöfer has proposed the following scale as a standard of the fitness of a water for brewing purposes, twenty-five flasks being each infected with one drop of water. In those cases in which certain micro-organisms develop neither in wort nor in beer, he describes the water as specially good. If development takes place in 10 per cent. of the wort flasks at the most, but not in the beer flasks, the water is good; if development takes place in 50 per cent. of the wort flasks and in none of the beer flasks the water is fit for use; if micro-organisms are present in more than 50 per cent. of the wort flasks, and in at most 19 per cent. of the beer flasks, the water is only to be employed in cases of necessity, and finally if the percentage of flasks of both categories exhibiting growths is higher than that above mentioned, the water is unfit for brewery purposes. It must be remembered here that chemical analysis has been entirely left out of account. Holm's Results.-In Holm's analyses of water from the Carlsberg Breweries, bacteria, moulds and yeast-like cells (Torula, Mycoderma) appear in the wort and beer, but no species of Saccharomyces. The presence of the latter is nevertheless not precluded, but their appearance in the water is at any rate rare. The species of moulds were especially numerous, not only in wort but also in beer; the same remark applies also as regards the number of growths. Bacteria were found along with these in the wort, whereas they appeared but seldom in beer. Yeast-like cells were rarely observed. Among the organisms observed by Holm in water the following may be named: Rhizopus nigricans, Penicillium glaucum, Mycoderma cerevisia, Bacterium aceti, and Bacterium Pasteurianum. In addition, Jörgensen and Lindner have found Sarcina. The latter investigator found it frequently, and supposes that a prolonged existence of the Sarcina germs in water renders them more capable of germinating in hopped wort. With regard to the importance of the micro-organism content of the water for brewery working, the germs present in the steeping water will be of little consequence in the manufacture of malt. There are, in fact, many germs on the surface of the barley corns, and the few which are added with the water are of little account. When the wort is boiled, these organisms are killed; they may, perhaps, be of some significance during mashing. The danger is naturally greatest in the fermentation and lager cellars; but other factors appear here, viz., low temperature and the large quantity of healthy yeast with its suppressing power, which restrain the development of the water germs. In carrying out a water analysis we must direct our attention to the cistern or the well from which the supply proceeds. Surface water, as is well known, contains a large number of germs, and these will increase to a large extent if the piping and the cistern are not kept properly clean. Hansen's Analyses of Air.-It is more difficult to obtain an average sample of air than of water. The same principles hold here as in water analysis. Hansen in his time used flasks with wort for investigating the circulation of yeasts and the organisms of the air in the various parts of a brewery. Large numbers of these flasks were left open at different times of the year at those places where he wished to analyse the air. The so-called vacuum flasks were also employed for the same purpose. The latter are flasks charged with culture liquid which are sealed during the boiling of the liquid; after cooling there is an airexhausted space over the culture liquid. If the sealed end is now broken off at the place where it is wished to examine the air, a certain quantity of air is sucked into the flask. The germs contained in this air are brought by shaking into contact with the culture liquid in which they then develop. In his last treatise on this subject Hansen recommends B FIG. 49.-Miquel's Flask, B, in combination with an aspirator, A. the passing of a certain quantity of air through sterile water, which retains the germs and can be subsequently analysed. An air analysis is, in short, performed in the same manner as a water analysis. For this purpose graduated pipettes are used or, where possible, Miquel's flask, which is represented in the accompanying drawing (Fig. 49) in union with an aspirator. The latter, A, is a bottle with an outflow tube, a, near the bottom, to which rubber tubing with a pinchcock is fitted. The neck of the bottle is closed by a bung through which a glass tube passes which is bent |