The Theory and Practice of Brewing

by Michael Combrune

Upon the whole, then, it appears, that a liquor fit for fermentation must be composed of water, acids smoothed over with oils, or saccharine salts, and a certain portion of elastic air; the heat of the air the liquor is fermented in, must be in proportion to the density of its oils; and lastly, that the pores are to be expanded by slow degrees, lest the air, by being admitted too hastily, should cause an effervescence rather than a fermentation, and occasion the whole to become sour. Wines, therefore, fermented in countries where the autumn is hot, require their oils to be more pinguious, than where the season is cooler. For the same reason beers are best made, when the air is at forty degrees of heat, or below the first fermentable point, because the brewer, in this case, can put his wort to work, at a heat of his own chusing, which will not be increased by that of the air; on the contrary, when, by its internal motion, the heat becomes greater, it will again be abated and regulated by the cold of the medium.

The pores of a wort are expanded in proportion to the heat it is impressed with; on which account common small beer, brewed in summer, when the air and acids more easily insinuate themselves into the liquor, ought to be enriched with oils obtained by hotter extracts, to sheath these salts; and in winter the contrary method must be pursued.

From this history of fermentation, we can, with propriety, account for the many accidents and varieties that accompany this act; and a comparative review of some of them may not be unnecessary.

A cold air, closing the pores of the liquor, always retards, and sometimes stops, fermentation; heat, on the contrary, constantly forwards this act; but, if carried too high, immediately prevents it.

A must, loaded with oils, will ferment with more difficulty than one which abounds with acids; it likewise is longer before it becomes perfectly fine; but, when once so, will be more lasting.

If the quantities of oil are increased, they will exceed the power both of the acids naturally contained in the must, and of those absorbed from the air in fermenting; the liquor will therefore require a longer time before it becomes pellucid, unless assisted by precipitation: and there may be cases where even precipitation cannot fine it.

These considerations naturally lead us to a general division of wines into three classes: First, of such as soon grow fine, and soon become acid, being the growth of cold countries. Secondly, of those which, by a due proportion of heat, both when the grapes germinate, and when they come to maturity, form a perfect must; and not only preserve themselves, but, in due time, (more especially when assisted by precipitation,) become transparent; and, thirdly, of such as, having taken their first form under the highest degrees of germination, (as I termed them) are replete with oils, disappoint the cooper, and render the application of menstruums useless, unless in such quantities as to change the very nature of the wine.

This remarkable difference in wines appears chiefly to arise from the climate; and it will confirm the observation before made, that, as wines are neither naturally nor uniformly perfect, they must be subject to many diseases.

All vegetable substances possess fermentable principles, though in a diversity of proportions; for those juices only, whose constituent parts approach to the proportion necessary for the act of fermentation, can be made into wines. I would not, however, from what I have attributed to a difference of heat in different climates, be understood, as if I thought that vegetables are more or less acid, more or less sulphureous, or in general more or less fermentable, merely from the heat of the country they grow in. This, though likely one of the principal causes of their being so, is by no means the only one; the form and constitution of the plant is another. In very hot climates, we find acid fruits, such as limes, tamarinds, lemons, and oranges; the proportions of fermentable principles in these fruits are such, as to render them incapable of making sound wines, though their juices may, in some degree, be susceptible of fermentation. In countries greatly favored by the sun, some vines and other fruit trees there are, which attract the acids from the air, and possibly from the earth, so greedily, that, when their juices are fermented, they soon become sour. On the contrary, in cold climates, we see warm aromatic vegetables grow, as hops, horse-raddish, camomile, wormwood, &c. whose principles cannot, without difficulty, and perhaps not perceptibly, be brought to ferment. But these instances must be accounted the extremes on each sides; for in cold, as well as in hot countries, fruits are produced susceptible of a perfect natural fermentation: with us, for example, apples; some species of which are endued with such austere and aromatic qualities, that their expressed juices ferment spontaneously, until they become pellucid, and are capable of remaining in a sound state many years. From hence it appears, that proper subjects, which will naturally ferment, for making wines, may be found in almost every climate. England, says Boerhaave, on this account, is remarkably happy: her fruits are capable of producing a great variety of wines, equal in goodness to many imported, were not our tastes but too often subservient, not to reason, but to custom and prejudice.