These results prove sufficiently that the same principle, applied with the same preparatory process, and with the same care and precautions, in general preserves all animal productions. But it is to be observed that in the previous cooking of each articles, it is to be only three-fourths dressed at the utmost, in order that the remainder of the requisite cooking may be communicated by means of the water-bath.
There are a number of articles which can bear an additional hour of boiling in the water-bath without any danger, as broth, gravy, jellies and the essences of meat, poultry and ham, the juice of the grape and of plants, &c. But there are also others which will sustain a great injury from a quarter of an hour’s or even a minute’s too much boiling. Thus the result will always depend upon the dexterity, intelligence and judgment of the operator.[J]
§ XI.
New-laid Eggs.
The more fresh the egg is, the longer it withstands the heat of the water-bath. I consequently took eggs the day they had been laid, placed them in a jar, with raspings of bread, to fill up the vacuities, and secure them against breaking when removed to a distance. Having well corked, tied and luted the jars, &c. I placed them in a boiler of a proper size[K] to give them seventy-five degrees of heat.[L] Having taken the water-bath from the fire, I took out the eggs as soon as the water was so cool that I could put my finger in it. I then took out the eggs and kept them six months. At the end of that period I took the eggs out of the jar, put them into cold water which I set on the fire, and heated it to seventy-five degrees: I found them fit to dip a toast of bread into, and as fresh as when I prepared them. As to hard eggs, which are to be cut into slices and fricaseed, I heat the water-bath eighty degrees, and as soon as it begins to boil, I remove the water-bath from the fire.
§ XII.
Milk.
I took twelve litres of milk fresh from the cow; I condensed it in the water-bath and reduced it to two-thirds of its volume, frequently skimming it. Then I strained it through a boulting cloth. When cold I took from it the skim which had risen while it was cooling, and bottled it, with the usual process, and afterwards put it in the water-bath which I let boil for two hours; and at the end of several months, I perceived that the cream had separated itself and was swimming in the bottle in the form of flakes. To obviate this inconvenience, I made a second experiment on a like quantity of milk which I condensed in the water-bath, reducing it to one half, instead of one third, as I had done the former. I then added to the milk, so reduced, the yolks of eight new laid eggs well beaten. Having left the whole thus well mingled half an hour on the fire, I completed the experiment as before. This expedient perfectly succeeded.
The yolk of egg had so completely combined all the particles, that at the end of a year, and even of eighteen months, the milk remained as fresh as when I put it in the bottles. The first also was preserved more than two years. The cream which was in flakes disappeared when put on the fire. Both sustained the boiling alike. From both, butter and whey were afterwards obtained. In the different experiments and chymical analyses to which they were exposed, it was found that the last, being much the better, was equal to the best cream sold at Paris to drink with coffee.