Imagens da página
PDF
ePub

of an over-abundant supply, or of a crop unfit for brewing purposes on account of blight or other causes.

The proportions of the different substances would be readily understood by paper-makers, and may be varied to suit their various requirements.

This invention claims to utilize materials hitherto valueless for any purpose except as a manure.

The claim protected by the patent is, the application and employment for the manufacture of pulp for paper-making of spent or fresh hops or spent malt, either alone or together, or in combination or not with other materials ordinarily used for paper-making.

At a meeting of paper-makers in France, in 1873, Messrs. Jourdeuil, Pauzot, and Gusses submitted samples of a textile material made from the bark of the hop stalk. By removing the outer skin, and subjecting it to chemicals, a textile substance was produced possessing length, suppleness, and delicacy of texture.

This is important to the hop farmer; for if the season should not prove favourable for the production of first-class hops, the paper-making material will compensate in some degree for this deficiency. No doubt the growth of hops will be introduced in future in many districts where they are not grown at present, as the large amount of material which they will supply for paper-making will alone ensure a good return for their cultivation.

The hop is also well known as a garden plant. It blossoms from June till August, and may be propagated by seed or by dividing the roots. It likes a deep, loamy soil, and is valuable as an ornamental climber over temporary arbours, trelliswork,

&c., in summer, as its leaves are very large and afford a fine shade. The "white bine" and the "grey bine" are the best sorts for this purpose; they succeed each other.

The flower, forming a spiked inflorescence, gives rise to scales, at the base of which the fruit is developed, protected against humidity by the resinous and very odoriferous powder of a golden yellow, named lupuline.

In a technical point of view, hops are the principal element in the brewing industry; but being very sensible to the action of air, they easily deteriorate, in spite of the generally practised compression; the essential oil which they contain becomes rancid and engenders a mouldiness, so that they do not keep longer than a year. To overcome this difficulty, and in order to give a more presentable aspect to his merchandise, the hop merchant has recourse to sulphuring, an operation always successful, but which at the same time produces a pernicious reaction on the essential oil, which thereby undergoes a chemical conversion. Under the action of the sulphurous' acid, which passes over the hops, the essential oil is oxidized, converted into valerianic acid, and combines with the sulphur to form a solid body. In this manner the oily matter of the hops is destroyed and the mouldiness prevented; but beer manufactured with sulphured hops will never be a wholesome beverage. The aroma of the hops is replaced by that of the valerianic acid, the sulphurous acid contained in the hops is partly converted into sulphuric acid, and the sulphur of commerce being arseniferous, the arsenious acid passes with the sulphurous acid in the hops, both are communicated to the beer, and may, although taken in small doses, inconvenience the consumer.

Another disadvantage is the action of the sulphurous acid on the tannic acid in converting it into gallic acid, which prevents the clarification and the fermentation of the beers, besides giving them a rough or sour flavour. The due preservation of hops with all their active and useful properties, without being subjected to sulphurous fumigation, has been the object of long researches.

Ten years ago a soft and dry extract of hops was manufactured, containing in a small volume the bitter, tonic, and aromatic principles of the plant, of which it represented very nearly the fifth. This soft extract is a kind of brownish preserve, which, as it will not keep long, the brewer does not care to utilize; the dry extract which is still manufactured is in a coarse powder, and keeps better; it is used to improve the bitterness of beers in course of manufacture when they are too sweet.

The question that has occupied so much time has at last been solved: the preservation of hops without sulphuring and without the extraction of their bitter and tannic principles. By chemical and mechanical means the green or freshly dried hops are separated from their essential oil, the great obstacle to their preservation, so that the strobiles remain whole, keep their original colour, the yellow dust at the base of the scales, and all their bitter and tonic principles, the aroma excepted. Hops thus treated and compressed will, it is said, keep for years.

The essential oil is preserved by itself in hermetically sealed bottles, and improves from year to year.

In the manufacture of beer, one operates with these hops as usual; and after the fermentation ten or twelve drops of

UNIVERSITY

AND CHEMISTRY OF HOPS.

CALIFORNIA

11

essential oil are added per hectolitre (22 gallons); the extraction of the bitter principle and of the tannin, the clarification and the fermentation are effected perfectly, the beer is of superior quality, very thin, limpid, clear, and creamy, being characterized by a delicious bouquet of hops, and keeps much better as, under the influence of the essential oil, the mycodemæ, microscopic animalculæ, which, by their presence in beer, cause an acetic and putrid fermentation, perish.

Chemistry of Hops.-Messrs. Payen and Chevallier, so far back as 1830, and even before, determined that the yellow secretion of hops, a bitter and aromatic element, was the sole source of the flavour, the strong odour, and, in fact, the active principle; and that the bracts of the cones which were not touched with the yellow substance, had no more aromatic odour or flavour than dry hay. They also ascertained that this yellow powder or secretion is found in varying proportions in different kinds of hops, and hence their real and useful value differs materially.

The following is the mode in which these able chemists made the analysis, which is more mechanical than chemical. "The strobiles, or cones, of the hops are taken when well dry, and the foreign matters which they contain are separated as much as possible; they are then placed on a fine horsehair sieve, pressed with the hand, and the sieve shaken; the pulverulent secretion passes through the meshes of the sieve, leaving the bracts on the top. These are again submitted to pressure and agitation, to separate any more of the yellow powder which may have escaped, until nothing is left but the waste bracts. Care, however, must be taken not to crush or bruise these, so that none may pass through the meshes to

augment the bulk of the sifted powder. This product can then be weighed and preserved in closed vessels."

Dr. Ives found, on analysis, the lupulinic grains to contain

[ocr errors][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small]

The following analyses are useful for reference, as showing the percentage quality of the different hops of commerce, chiefly those of the Continent:

[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small]

Turpin recognized in the glands of the hops the presence of two vesicles in which an etherized oil existed, and Raspail, by a more careful examination, found chlorophyl, a resinous substance, an etherized oil, and some gluten in them. Payen and Chevallier analyzed hops from different sources, and they

« AnteriorContinuar »