“The following were the proportions of fats I recovered, viz.—
| Lard | 60 | per cent. |
| Mutton fat | 75 | ” |
| Beef fat | 95 | ” |
The precipitated mutton fat is powdery, and white as snow. Lard and beef are more adherent and greasy; for that reason mutton makes the firmest compound.”
7. On the Cooling of Fats. At a meeting of the University of Edinburgh Chemical Society, held on March 13th, 1878, a paper on the above subject was read by Mr Treharne, M.B.C.M., wherein the author states:—“If equal bulks of the fats of mutton, beef, pork, and butter, and palm oil be heated to 100° C. in small flasks fitted with a thermometer through the cork, and then allowed to cool by radiation under the same conditions for each, temperature is found to fall regularly to a certain point (which is different for each of the facts above named) and then to rise to a certain turning point. These turning points are approximately as follows:—
| For | Mutton | fat | 40° | C. |
| ” | Beef | ” | 28·5° | C. |
| ” | Pork | ” | 26·5° | ” |
| ” | Butter | ” | 23·5° | ” |
| ” | Palm oil | 21·0° | ” |
The extent of the rise in temperature is different in each fat, being greatest in that of mutton, and least in that of butter and palm oil. The extent of the rise is also greater within certain limits the greater the quantity of fat employed; but as a rule the turning point is pretty constant for the same fat. There is also a little difference in the turning points and the extent of rise according to the part of the carcase from which the fat has been taken. If temperature and time be taken as co-ordinates, and the rate of cooling be represented by curves, these latter will be characteristic of the respective fats. A mixture of equal parts of mutton and butter fats does not give a curve intermediate between those of its two components; but is such as to indicate that less heat is given out on cooling (to 20° C say) than in the case of butter, which, compared with mutton fat, gives off very little heat.”
For further information on the subject of ‘Butter’ the reader is referred to a Report by Mr Bell—the principal of the Chemical Laboratory at Somerset House—to the Board of Inland Revenue, included in a return made to the House of Commons in 1876.
Preservation. 1. Melt the butter in a stoneware or a well-glazed earthen pan set in a water bath at a heat not exceeding 180° Fahr., and keep it heated, skimming it from time to time until it becomes quite transparent; then pour off the clear portion into another vessel, and cool it as quickly as possible by placing the vessel in very cold water or ice. This is the method employed by the Tartars who supply the Constantinople market. In this state it may be preserved perfectly fresh for 6 or 9 months, if kept in a close vessel and a cool place. This is the plan so strongly recommended by M. Thénard. Mr Eaton states that butter melted by the Tartarian method, and then salted by ours, will keep good and fine-tasted for two years.
2. Saltpetre and white sugar, of each 1 oz.; best Spanish great-salt (or Cheshire large-grained salt), 2 oz.; all in very fine powder; mix thoroughly, and add 1 oz. of this mixture to every lb. of butter, and thoroughly incorporate them together. The butter thus prepared is then to be tightly pressed into clean glazed earthenware vessels (or well-seasoned casks), so as to leave no vacuities. This plan is recommended by Dr Anderson, who declares that “butter so prepared will keep in a cool place for years; and will bear a voyage to the East Indies, if packed (stowed) so as not to melt.” It does not taste well before it has stood for three or four weeks, after which it acquires a rich marrow-like flavour, which no other butter ever possesses. A good method to preserve the butter from the air is to fill the pots to within an inch of the top, then to lay on it some coarse-grained salt to the depth of a 1⁄4 to 1⁄2 an inch, and lastly to cover each pot with a slate, plate, or other flat article. The salt by long keeping runs to brine, which forms an air-tight layer on the top of the butter, and may at any time be very easily removed by turning the pot on one side.
3. Fresh butter, 21 lbs.; salt, 1 lb.; saltpetre, 1 oz. These are the common proportions for the best salt butter of the shops.