The determination of the amount of ‘solids, not fat,’ is, in almost every instance, all that is necessary to enable an opinion to be arrived at as to whether the sample of milk has had water added to it or not.
Out of fifty-six samples of milk supplied to the different London unions in 1873, Professor Wanklyn reports that he found only fifteen unwatered, or nearly unwatered. Of these fifteen samples nine had been skimmed, leaving only six that were at once unwatered and unskimmed. These figures, therefore, show that only about 10 per cent. of the milk supplied in the above year to the Metropolitan unions was genuine. He adds—“It is curious to compare the language of the contract under which (as it appears from Mr Rowsell’s report) the dealer supplied the various unions with milk, with the quality of the article as exhibited by the analysis. ‘New unskimmed milk unadulterated,’ ‘genuine as from the cow,’ ‘best
new unskimmed milk, to produce 10 per cent. of cream,’ occur in these contracts.”
Prop. These are well known. Perfectly fresh milk is slightly alkaline, but soon becomes acid on exposure to the air, and after a time white coagula of casein (CURDS) separate from it. This change is immediately effected by the addition of rennet or an acid. That from the first, when dried and pressed, constitutes cheese.
Pur., Tests, &c. The common frauds practised by the milk-dealers are the addition of water and the subtraction of part of the cream. Sometimes potato starch is added to the milk, to give it a creamy or rich appearance, and this addition is still more frequently made to cream, to increase its consistence and quality.
The presence of potato starch may be determined by boiling some of the milk with a little vinegar, and after separating the coagulum by a strainer, and allowing the liquid to become cold, testing it with solution or tincture of iodine. If it turns blue, starch, flour, or some other amylaceous substance, has been used to adulterate it. In most cases it will be sufficient to apply the test to the unprepared suspected milk.
It has frequently been stated that chalk, plaster of Paris, gum, gelatin, sugar, flour, mucilage of hemp-seed, the brains of animals, and other similar substances, are often added to London milk, but there is no reason to suppose there is any truth in these assertions, as some of these articles are too costly to be used, and the presence of others would so alter the flavour or appearance of the milk, or would so soon exhibit themselves by subsidence, as to lead to their detection.
Pres. Milk may be preserved in stout bottles, well corked, and wired down, by heating them, in this state, to the boiling-point, in a water bath, by which means the oxygen of the small quantity of enclosed air becomes absorbed. It must be afterwards stored in a cool situation. By this method, which is also extensively adopted for the preservation of green gooseberries, green peas, &c., milk will retain its properties unaltered for years. A few grains of carbonate of magnesia, or, still better, of bicarbonate of potassa or soda, may be advantageously dissolved in each bottle before corking it.
Under Bethel’s patent the milk or cream is scalded, and, when cold, strongly charged with carbonic-acid gas, by means of a soda-water machine, and the corks are wired down in the usual manner. The bottles should be kept inverted, in a cool place.
An excellent method of preventing milk from turning sour, or coagulating, is to add to every pint of it about 10 or 12 gr. of carbonate or bicarbonate of soda. Milk thus prepared may be kept for eight or ten days in temperate weather. This addition is harmless, and, indeed, is advantageous to dyspeptic patients. According to D’Arcot, 1⁄2000th part