By WAYNE B. BISSELL, PH.G.
From an inaugural essay.
In discussing this subject the main object of the writer will be to bring to notice an extract of Hops made by an entirely new process, and to compare that product with one made by myself, according to the directions given in the Dispensatory.
A very fine sample of late hops, which appeared rich in lupulin, was exhausted as thoroughly as possible with pure alcohol by percolation. The drug was then boiled in water for one hour, strained and washed. The alcoholic and watery extracts were evaporated at a very low temperature to a thick syrup and then mixed, and further evaporation carried on by means of a water bath until a product of nearly pilular consistence was obtained, in which condition the patent extract was. The product thus obtained, contained the aroma of the hop which is very easily destroyed by a high heat.
As far as could be learned, the process by which the patent extract is made on a very large scale is as follows:
The hops taken from the bale are run through a machine, which separates the scales from the axis without breaking them much. They are now placed in a large wire cage rather loosely, and three of these cages are run into an immense boiler or "extractor" as it is called, which holds about six hundred pounds of the drug. A heavy door then is shut and barred, making everything secure. About three hundred barrels of gasoline are now pumped in by the engine, when, by means of a steam coil, heat is applied until a pressure of one hundred pounds to the square inch has been attained. The object of this high pressure is to break or crush the little glands called lupulin, which contain the valuable principle, this being taken up by the hot gasoline. As soon as the above pressure has been attained, the steam is shut off and as the heat decreases, the hot gasoline holding the extract in solution is drawn off gradually into a large boiler or tank, and as it gradually cools, the extract settles to the bottom and the gasoline rising to the top is removed and used over again on a fresh portion of hops. In the meanwhile the extract and gasoline remaining in the extractor, have been completely washed out by superheated steam and both separated as in the former case, so there is but very little waste of menstruum. The extract in the boiler on cooling to a certain temperature, is drawn off and subsequently canned, in which condition it will keep for an indefinite period, a great advantage over the hop itself, which at the end of two years is nearly useless. One pound of this extract represents. about twelve pounds of choice hops. About two thousand pounds of hops can be exhausted in these works during twenty-four hours. The only use made of this extract at present is in the manufacture of beer, for which purpose it is at present being used to a large extent in Philadelphia and New York, fully supplying the place of the ordinary hop.
On investigation quite a difference was observed between this extract and the one made by myself, the former being of an intense black color, appearing to be more oily, and containing practically no tannin or a mere trace, while in the extract made by myself between 7 per cent. and 8 per cent, of tannin was indicated by using a solution of acetate of lead.
The amount of glucose was ascertained by Fehling's solution, and found to be in my extract 12 per cent., but in the patent extract, a little over 16 per cent. During this investigation the writer obtained results more easily from the patent extract than from the extract made by himself.
On exposing the extract made by me to a temperature of 100°C. until it ceased to lose weight, 13 per cent. of volatile matter was expelled, and at 110°C. it lost an additional 9 per cent.; becoming quite dry, darker in color, losing its aroma and breaking with little difficulty into small pieces. The patent extract exposed to 100°C. lost only .05 per cent. in weight and at 110°C., this loss was increased by only an additional .03 per cent. This high heat seemed to have but very little effect on it, either in changing its color, or destroying its odor.
The effect of different solvents on the two extracts showed a very marked difference. Water dissolved only a very small portion of the extract made by me, leaving a brown residue, which was apparently mostly resin and oil. Alcohol had only a slight effect, but dilute alcohol took up more. All of the ordinary solvents were tried, and none of them completely dissolved this extract.
The patent extract, was found to be practically insoluble in water, and also in cold alcohol, but hot alcohol held it in solution as did also benzin. It is more soluble in ether and completely soluble in chloroform. It has a very strong and rather unpleasant odor, and its taste is exceedingly bitter. A further point of interest concerning this extract is, that when it is being drawn from the storing boiler into large cans, quite frequently small white crystals are seen, but it is impossible almost to separate them. The extract without purification, so as to free it entirely from the gasoline, could not be used internally as it creates nausea, but is quite frequently mixed with sugar and formed into cakes in which condition it is used to some extent.
In conclusion, the writer would extend his thanks to W. A. Lawrence, Superintendent of the works, through whose kindness he obtained the process of manufacture as given above.
The American Journal of Pharmacy, Vol. 57, 1885, was edited by John M. Maisch.