In the kitchen the test may be conducted as follows: Using as the source of heat an ordinary kerosene lamp, turned low and with chimney off, melt the sample to be tested (a piece the size of a small chestnut) in an ordinary tablespoon, hastening the process with a splinter of wood (for example, a match). Then, increasing the heat, bring to as brisk a boil as possible, and after the boiling has begun, stir the contents of the spoon thoroughly, not neglecting the outer edges, two or three times at intervals during the boiling - always shortly before the boiling ceases. In the laboratory a test tube, a spoon, or sometimes a small tin dish, is used in making this test. From the last-named utensils the test is often called the "spoon test," and sometimes the "pan test".
A gas flame, if available, can be used perhaps more conveniently than a kerosene lamp.
Oleomargarine and renovated butter boil noisily, sputtering (more or less) like a mixture of grease and water when boiled, and produce no foam, or but very little. Renovated butter produces usually a very small amount.
Genuine butter boils usually with less noise, and produces an abundance of foam.
To Distinguish Oleomargarine from Genuine and Renovated Butter.
The utensils required in the test to distinguish oleomargarine from renovated and genuine butters are as follows:
(1) A one-half pint tin "measuring cup," common in kitchen use, marked at the half and quarters; or a plain one-half pint tin measure, ordinary narrow form , or an ordinary small tin cup, 2 3/4 inches in diameter and 2 inches in height, holding about one gill and a half.
(2). A common kitchen pan, about 9 1/2 inches in diameter at the base.
(3). A small rod of wood, of the thickness of a match and of convenient length for stirring.
(4). A clock or watch.
The process for distinguishing oleomargarine from renovated and genuine butters is as follows:
Use sweet skimmed milk, obtained by setting fresh milk in a cool place for twelve to twenty-four hours and removing cream as fully as possible. Half fill with this milk the half-pint cup or measure, or two-thirds fill the smaller cup mentioned, measuring accurately the gill of milk when possible; heat nearly to boiling, add a slightly rounded teaspoonful of the butter or butter substitute, stir with the wooden rod, and continue heating until the milk "boils up," remove at once from the heat and place in the pan (arranged while milk and fat are heating), containing pieces of ice with a very little ice water, the ice to be mostly in pieces of the size of one to two hens' eggs (not smaller, as small fragments melt too rapidly) and sufficient in quantity to cover two-thirds of the bottom of the pan; the water to be in quantity sufficient, when the cup is first placed in the pan, to reach on the outside of the cup to only one-fourth the height of the milk within; any water in excess of that amount must be removed. (This refers to the condition at the beginning of the cooling; later, as the ice melts, the water will rise to a higher level.) Stir the contents of the cup rather rapidly, with a rotary and a cross-wise motion in turn, continuously througbout the test, except during the moment of time required for each stirring of the ice and water in the pan, which must be done thoroughly once every minute by the clock. This is done by moving the cup about, in a circle, following the edge of the pan. Proceed in this manner for ten minutes, unless before that time the fat has gathered or has allowed itself to be easily gathered in a lump or a soft mass, soon hardening. If it so gathers, the sample is oleomargarine; if not, it is either genuine or renovated butter".
It will be seen that by trying both of these tests one may determine which of the three a suspected sample of butter really is.
A method of determining the presence of coal tar dyes in foods has been given in the following words by a recent writer:
"Suppose that some cheap currant jelly is to be examined. Stir up about one-fourth of the contents of the tumbler of jelly with about a pint of water in an agate stewpan. Take a piece of white woolen cloth about five or six inches square and wet it thoroughly with boiling water. Care should be taken that it is "all wool," and white is better than cream color. Nun's veiling is an excellent thing to use. Immerse the cloth in the diluted jelly and boil it on the stove for five or ten minutes, stirring it frequently with a small wooden stick. Then remove it and wash well in boiling water. If a dye has been used in the jelly the cloth will be brightly colored.