Milk has been preserved in the following manner: Fresh milk is reduced by boiling to one-half, and beaten up with yolk of eggs, in the proportion of eight eggs to every ten and a half quarts of milk. The whole is then placed on the fire for half an hour, and skimmed frequently; it is next strained and heated in a water-bath for two hours. It is stated that this milk will keep good for two years, and, if churned, would afford good butter. Cream may be preserved by boiling five measures down to four; then, after cooling and skimming, it is put into a bottle, corked down, luted, and kept in the boiling heat of a water-bath for half an hour. This, it is said, will keep two years.
A much better method of preserving milk is that first pointed out by M. Dirchoff, the Russian chemist; namely, to solidify it by driving off the aqueous portion by a gentle heat. Specimens of consolidated milk were shown in the Great Exhibition; and it was stated that, after being dissolved in boiling water, and reproduced in the form of milk, the solution will keep pure for four or five days. As milk contains 873 parts of water in every 1000, it follows that 1000 parts of milk will yield by evaporation only 127 parts.
7. Potting is only another contrivance for excluding animal substances from contact with air. Lean meat should be selected, cooked, and then reduced to a pulp by being beaten in a mortar, salt and spices being incorporated. The pulp is then rammed into jars, and preserved from the air by a thick coating of melted butter or lard poured over it.
In the preservation of fruits and vegetables, some are dried, as in the case of nuts, raisins, sweet herbs, &c.; others are preserved by sugar, such as many of the fruits, whose delicate juices would be dissipated in the process of drying. Some are preserved in vinegar, as in the case of pickles; a few by salting, as French beans; and others are preserved in spirits.
Appert's method applies to vegetables and fruits of all kinds; they need not, however, be parboiled. The dry and fresh-gathered fruits are put into strong, wide-mouthed glass bottles, carefully corked, and luted with a cement of lime and soft cheese, and bound down with wire. The bottles are then inclosed separately in canvas bags, and put into a kettle of water, which is gradually heated until it boils; the bottles are kept in this condition until the fruits are boiled in their own juice. The whole is then left to cool; after which the bottles are examined separately, and put away for store.
Many kinds of vegetables may be preserved by being spread out on the floor of a kiln, and dried by a gentle heat: the thicker kinds of roots, such as carrots, turnips, potatoes, &c., are to be sliced, and thoroughly well dried; after which they must be packed up in paper or very dry boxes, and put into casks.[3]
A method of preserving vegetables by drying and pressure, recently invented by M. Masson, was brought into prominent notice at the Great Exhibition. Cabbage, sliced turnips, apples, or whatever vegetable be selected, are dried in an oven at a certain temperature, so as to drive off from seven to eight per cent. of water: the drying must not be conducted too slowly nor too rapidly, but at a medium rate. After the drying, the vegetables are packed into a very small compass by the intense pressure of an hydraulic press; then squared and trimmed with a knife, packed up in tinfoil, and lastly, stored in boxes. A short time ago, we examined some red cabbage preserved in this way, which had been exposed in the Great Exhibition all the time it was open, and had been slowly absorbing moisture, and yet it appeared to be perfectly good. By this method, from 15,000 to 18,000 rations, of a quarter pound each, can be stowed into a cubic yard. We also saw some dried plantains from Mexico (a vegetable of very considerable nutritious value), which had been lying in a warehouse at Woolwich ever since the year 1835, and had undergone no change. It was stated that the method of preparing them is cheap and easy, and that the dried plant can be sent in any quantities to Europe, at six cents per pound, with a considerable profit to the importer.
Some kinds of vegetables, such as French beans, artichokes, olives, samphire, and barberries, are preserved by salt, a strong brine being made by the addition of four pounds of salt to a gallon of water; the vegetables are put into this, and quite covered with it. In Holland and Germany, kidney beans are sliced by a machine something like a turnip-cutter, and put into a cask in layers with salt between; a weight is then put on, and pressure is kept up until a slight fermentation takes place; the salt liquor is then poured off; the cask is covered up, and put into the cellar as store. Before being cooked, the beans are steeped in fresh water.
Sauer Kraut is prepared somewhat in the same manner. The following recipe for making it is given by Parmentier:—
The heads of white winter-cabbages, after removing the outer leaves, are to be cut into fine shreds, and spread out upon a cloth in the shade. A cask which has had vinegar in it is to be selected, or, if that cannot be had, the inside should be rubbed over with vinegar or sauerkraut liquor. A layer of salt is to be put in the bottom of the cask, caraway-seeds are to be mixed with shreds of cabbage, and they are to be packed in the cask to the depth of four or six inches; and layers of this kind, with salt between each layer, are added till the cask is full, stamping them down with a wooden stamper as they are put in, to half their original bulk; some mix a little pepper and salad oil with the salt. Some salt is to be put on the top, and some of the outside leaves of the cabbages. About two pounds of salt suffice for twenty middle-sized cabbages. The head of the barrel is to be placed upon the cabbage-leaves, and must be loaded with heavy stones. A common method is for a man, with clean wooden shoes on, to tread the cabbage down in the cask. Fermentation will take place, and some juice will be given out, which is green, muddy, and fetid; this rises to the surface, and is to be replaced with fresh brine. When the fermentation is over, the casks are closed up. Cabbages are preferred, but any other vegetables may be treated in the same manner.