FININGS.
All sorts of beer, if sound and well brewed, will, in due time, become bright; but when drank so new as is generally the practice, fining is absolutely necessary to give it that brilliant transparency which is so pleasant to the eye, and without which the best beer would be objected to.
The most efficient fining for beer which we have yet discovered is isinglass; the best of which is obtained from the sounds of the sturgeon, a fish found in the Danube, and rivers of Muscovy. In this country an inferior sort is prepared from the sounds of cod-fish, or ling; or, indeed, from any other fish: and also from the skins of soles.
The best isinglass is nearly all gelatine, and contains ninety-eight parts in every 100 which are soluble in boiling water. Isinglass varies in price from 1s. 6d. to 16s. per lb. There are various modes of ascertaining its value: and we extract two modes from a paper on the subject by Mr. S. Roberts, in Dr. R. D. Thomson's Records of Science, No. 14., pp. 106, 107.
“A great variety of isinglass is offered for sale, at a range of prices from 3s. to 16s. per pound; and the relative value of each kind may be known by the following tests:—
“In the first place, isinglass should remain unchanged, by being steeped in spirit of wine or alcohol, from 50° to 60° over proof, in which gelatine (the chemical principle of isinglass) is insoluble. The alcohol, or spirit of wine, in which the isinglass has been steeped, should then be tried with a few drops of tincture of galls; if the liquor remain clear and unchanged, it is much in favour of the character of the isinglass. If, on the other hand, the tincture of galls causes a precipitate from the alcoholic liquor, the isinglass is not pure, as it contains something more than pure gelatine.
“Different samples of isinglass, which have remained unchanged in alcohol or spirit of wine, should also be tried by the two following methods, before an opinion can be given as to their relative value. Try given weights of each sample (one-eighth of an ounce, for instance) in three ounces of water by measure, in separate vessels; bring them gradually to a boil, occasionally stirring each sample. While hot, strain the different solutions through muslin, into separate vessels. In proportion to the quantity of undissolved matter left upon each strainer, may the solubility of the different samples be ascertained; that which leaves the least residuum will form, when cold, the strongest jelly, upon which the clearing property of isinglass depends. The remaining trial to which the different samples are to be submitted, is the last and most decisive one. Equal weights of each sample (the one-fourth of an ounce, for instance) are to be cut into very small pieces, and each one-fourth of an ounce put into half a pint (imperial measure) of hard or sour beer, and the several vessels containing the different samples put into an apartment, at from 65° to 75° F., and allowed to remain there for three days, stirring each sample very well, once or twice a-day.
“At the expiration of that time, there will be an evident difference in the strength of each jelly, provided different qualities of isinglass had been submitted to the experiment; and when the thickest jelly has a small quantity of the tincture of galls applied to it, and stirred through it, it will separate the gelatine from the sample of isinglass in the form of a thick jelly. The other samples which afforded a less solid jelly will give, with tincture of galls when stirred through it, a smaller quantity of gelatine in the form of thick jelly.
“From the strength of the jelly given by any sample of isinglass steeped in the above proportion of sour beer (such as brewers use in making clearings), and submitted to a temperature not exceeding 75° F., may be ascertained the relative value of that sample, as upon the strength of the jelly, and, consequently, the quantity of gelatine contained in any isinglass, depends its value in clearing malt-liquor. The best short-staple isinglass is always soluble in boiling water to about 1⁄50 residue.”
From the following quotations, however, it will appear that there are objections to the use of isinglass in fining beer, except for immediate use. Berzelius, who had discovered a small quantity of lactic acid in all animal fluids, and in muscular fibre, gave it as his opinion, in 1834, that lactic acid is produced in all fermentable matter. This suggestion has been confirmed by Vanden Ghyen of Ghent, who has extracted it from the beer of Diest: De Koninch has obtained the same acid from the brown beer of Malines. One litre of the beer of Diest afforded 2.20 grams of syrupy lactic acid. (L’Institut, 284.) “M. Fremy says that the internal membrane of the stomach of the calf is capable of transforming any aqueous solution of sugar into lactic acid.” (L’Institut, 286.)
“M. Gay Lussac cautions, however, against the conclusion, that this change is an organic one, since it is possible that the transformation may be due to an action purely chemical between the saccharine and organic" matter. Indeed, we know that lactic acid is in many cases produced by the contact of animal with vegetable substances.” (L’Institut, 288.)
Mode of preparing Finings.
Having thus stated objections which may be raised as to using isinglass for fining beer, we shall give the mode of preparing it for use. Chemists state that gelatine is dissolved in liquid alkalis. The common mode, however, of converting isinglass into finings for beer, is by dissolving it in the first place by acids. Let any quantity be taken which may be thought necessary according to the magnitude of the brewery, and placed in an open-headed cask: if cut into shreds it will dissolve the more quickly. Let it then be covered to the depth of five or six inches with vinegar, which is the best solvent, or with very acid old beer. When the isinglass has swelled up so as to have absorbed all the vinegar or old beer on the top, more vinegar or old beer must be added, again covering the mass to the depth of five or six inches: the mixture should then be vigorously stirred with a hard broom, and the same process repeated as the isinglass goes on swelling, until the whole becomes of the consistence of pulp or thick jelly. Whatever quantity may then be wanted for use, may be taken out and put into another open-headed vessel, where it is to be mixed up with weak bright beer (generally brewed for the purpose), until brought to its proper consistency for use. This should then be strained through a fine hair-sieve by rubbing it through the sieve with a hard hair-brush, into another open-headed vessel: the portion which cannot be passed through the sieve may be returned to the first vessel, until again wanted. No more vinegar or old beer should now be used; the isinglass in the first cask must still, as it keeps swelling and thickening, be thinned down with the thin bright beer, until in a fit state for being passed through the sieve as before, and the quantity wanted for immediate use can at any time be made as before directed.
How to be Used.
When finings are properly made, they should be transparent, and no undissolved particles of the isinglass should be seen in them: the specific gravity should not be above 1.025. All sound well-brewed beer will readily become bright with finings as above described; but there are other sorts of beer which will not be rendered bright by any finings, and in this case, finings will be rather detrimental than otherwise. If, therefore, there should be any doubt as to the aptitude of the beer to take finings, it should in the first place be tried. This may be done by taking a small quantity of the beer from the vat, or whatever other vessel it may be contained in, and putting it into a long glass vessel made for the purpose. To this add a teaspoonful or more of the finings; it must then be shaken so as to mix thoroughly the finings with the beer; if the beer is sound, and has been well brewed, its aptitude to become bright will be soon shown, by the mixture becoming thick and curdy: a bright portion will generally make its appearance at the bottom or middle, and the finings will gradually mount up to the top, taking all impurities along with them, and leaving the remainder brilliantly bright. It has by some been stated that the finings should have a contrary effect, and at once carry the impurities from the top to the bottom. This, however, is a mistaken idea, and only takes place with what is called stubborn beer, and which will not become thoroughly bright whatever quantity of finings may be added to it. Should the sample in the glass become bright, there can be no doubt that the bulk will be affected in the same manner; but if not, there can be no advantage in applying finings, as they must produce more harm than good.
The more pure the isinglass, the more finings can be made from the same weight. Some are in the practice of dissolving the isinglass in boiling water to make finings; this is not only a very expensive, but also a very erroneous mode of proceeding, as the finings, when thus made, will immediately coagulate upon being applied to the beer, and at once go to the top or bottom without producing the desired effect. It may be observed that hot water, warm beer, or even steam, when applied to isinglass, does not hasten the solution, but on the contrary, hardens it, converting it into a dense fibrous mass, from which very little fining can be obtained.