CHAPTER XXII.
CHEMISTRY AND TOXICOLOGY OF MUSHROOMS.
By J. F. CLARK.
Regarding the chemical composition of mushrooms, we have in the past been limited largely to the work of European chemists. Recently, however, some very careful analyses of American mushrooms have been made. The results of these investigations, while in general accord with the work already done in Europe, have emphasized the fact that mushrooms are of very variable composition. That different species should vary greatly was of course to be expected, but we now know that different specimens of the same species grown under different conditions may be markedly different in chemical composition. The chief factors causing this variation are the composition, the moisture content, and the temperature of the soil in which they grow, together with the maturity of the plant. The temperature, humidity, and movement of the atmosphere and other local conditions have a further influence on the amount of water present.
The following table, showing the amounts of the more important constituents in a number of edible American species, has been compiled chiefly from a paper by L. B. Mendel (Amer. Jour. Phy. 1: 225–238). This article is one of the most recent and most valuable contributions to this important study, and anyone wishing to look into the methods of research, or desiring more detailed information than is here given, is referred to the original paper.
Table I.
| FRESH MATERIAL. | IN WATER-FREE MATERIAL. | |||||||
| WATER. | DRY MATTER. | TOTAL NITROGEN. | PROTEID NITROGEN. | ETHER EXTRACT. | SOLUBLE IN 85 PER CENT ALCOHOL. | FIBRE. | ASH. | |
| % | % | % | % | % | % | % | % | |
| Coprinus comatus | 92.19 | 7.81 | 5.79 | 1.92 | 3.3 | 56.3 | 7.3 | 12.5 |
| Morchella esculenta | 89.54 | 0.46 | 4.66 | 3.49 | 4.8 | 29.3 | 8.7 | 10.4 |
| Polyporus sulphureus | 70.80 | 9.20 | 3.29 | 2.23 | 3.2 | 27.8 | 3.0 | 7.3 |
| Pleurotus ostreatus | 73.70 | 6.30 | 2.40 | 1.13 | 1.6 | 31.5 | 7.5 | 6.1 |
| Clitocybe multiceps | 89.61 | 0.39 | 5.36 | 1.98 | 6.0 | 57.2 | 9.6 | 11.5 |
| Hypholoma candolleanum | 88.97 | 1.03 | 4.28 | 2.49 | 2.5 | 44.4 | 12.1 | 13.9 |
| Agaricus campestris | 91.8 | 8.2 | 4.75 | 3.57 | 3.72 | —— | —— | 11.6 |
Water.—Like all growing plants, the mushroom contains a very large proportion of water. The actual amount present varies greatly in different species. In the above table it will be seen that Polyporus sulphureus, with over 70 per cent. of water, has the least of any species mentioned, while the species of Coprinus and Agaricus have usually fully 90 per cent. water. The amount of water present, however, varies greatly in the same species at different seasons and in different localities, and with variations in the moisture content of soil and atmosphere, also with the age and rapidity of development of the individual plant.
Total Nitrogen.—The proportion of nitrogen in the dry matter of different species varies from 2 per cent. to 6 per cent. This comparatively high nitrogen content was formerly taken to indicate an unusual richness in proteid substances, which in turn led to very erroneous ideas regarding the nutritive value of these plants. The nitrogenous substances will be more fully discussed later, when we consider their nutritive value.
Ether Extract.—This consists of a variety of fatty substances soluble in ether. It varies greatly in quality and quantity in different species. The amount is usually from 4 per cent. to 8 per cent. of the total dry matter. It includes, besides various other substances, several free fatty acids and their glycerides, the acids of low melting point being most abundant. These fatty substances occur in the stem, but are much more abundant in the cap, especially in the fruiting portion. Just what nutritive value these fatty matters may have has never been determined.