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 A D U L T E R A T I O N specific gravity of a milk being known and its contents in fat, the proportion of solids-not-fat can be calculated. Formulae for that end have been worked out by a number of chemists. An analysis of milk, showing the specific gravity, the percentage of fat and that of solids-not-fat can therefore now be made in as many minutes as the hours formerly required, and in scientifically conducted dairies the price paid for the milk is regulated by the analytical data obtained. No forms of adulteration occur except the addition of water, the removal of cream (or its equivalent, the addition of skim-milk), and, if adulteration it be, the addition of preservatives. All statements as to the occurrence of chalk and of sheep’s brains are fables. Although the addition of water is still a common form of adulteration, the percentage of added water is mostly not greater than from 8 to 15, and the grosser and more impudent frauds commonly met with twenty years ago have practically been stamped out. A number of the large dairies supplying London and other large towns have fully equipped laboratories, with a staff of highly trained chemists, analysing almost each churn of milk delivered by the farmers, adulteration being thus as completely prevented as possible. Against the skimming of milk the means available are not so effective as those against watering, as the natural variation of the amount of fat is so considerable, partially skimmed Jersey milk still containing as much fat as unaltered milk from lowland cattle. Butter.—Since the introduction of margarine, frauds in the butter trade are exclusively confined to two kinds— namely, the substitution of margarine for and the addition of margarine to butter, and the incorporation or undue retention of water. Referring firstly to the latter form of adulteration, it must be borne in mind that all butter contains water. Properly-made butter contains, as a rule, 11 to 15 per cent.; it is not practicable to remove a larger proportion by rolling or squeezing, as the consistency of the butter suffers; 16 or at most 17 per cent, of water may legitimately be present in good butter. If, however, the churning of the cream is carried out at too high a temperature, an emulsion of water and butter is formed, containing as much as 30 or even 40 per cent, of water, causing the article to assume an ointment-like appearance. In properly-equipped dairies, refrigeration of the cream, if needful, is adopted to reduce the temperature of the cream in summer; but in small and old-fashioned dairies, as in many of those in the West of Ireland, these means are not available, and Irish butter, therefore, often contains an excess of water, 25 per cent, and over. As in most cases magistrates have declined to consider this as an adulteration, and often enough the petty farmers are not to be blamed, the wilful introduction of water into butter has at times been carried out on an industrial scale, and even at the present time much butter is sold which has been loaded with water up to 28 and more per cent., with of course good profit to the “ manufacturer.” Chemical differentiation between butter and butter-substitutes, now called margarine, was unknown prior to 1873, when the writer, with A. Angell, published a method which readily allowed of such differentiation, and of the estimation of the proportions of butter-fat and other fat contained in a mixture, based upon the fact that while fats other than butter-fat (and cocoa-nut oil) contain about 95‘5 per cent, of fatty acids insoluble in water, butter-fat contains a smaller quantity—namely, about 86 to 88 per cent.—the difference being due to the presence of a, corresponding amount of water-soluble fatty acids. Various modifications and simplifications of this principle have since been worked out, and the detection of margarine in butter, if present in substantial amount, has been rendered

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easy and certain. In the case of butter, as in that of milk, the analyst has, however, to reckon with natural variations in the composition of the butter-fat itself, and no means have yet been discovered whereby percentages smaller than 10 per cent, can be discovered with sufficient certainty to lead to the conviction of the vendors. It is a singular fact that while, as a rule, the composition of the butter-fat is almost independent of the food of the animal, under some conditions depending mainly upon the period of lactation, the composition of the fat undergoes material changes, so that a cow in the last stages of lactation may yield milk, small in quantity, from which butter can be churned which analyses as if it were a mixture of butter and margarine. Luckily it happens but rarely in practice that all the cows of a whole herd become “dry” at the same time; hence the natural variation in composition equalizes itself as a rule. There are, however, a few cases on record, notably one carefully worked out by A. H. Allen, in which butter was made under strict supervision in Denmark from absolutely pure materials, yet analysed like a mixture. It is doubtful therefore whether adulteration of butter with small amounts of margarine can ever be quite prevented by certain discovery, especially if the admixture is made, as in some parts of Holland, with the active aid of skilled chemists. When it is considered that England imports about ten million pounds sterling worth of butter per annum, the immense importance of preventing substitution of margarine, of approximately half the price of butter, will be apparent. Some most ingenious instruments have been constructed, notably Abbe’s refractometer, with a view to obtain by physical means data for discrimination between butter and mixtures. Melted butter-fat refracts light to a less degree than do butter-substitutes; the instrument in question allows of the determination of the “ index of refraction ” by the use of a mere droplet of the butter-fat, and is a most valuable tool in the hands of the chemist. Cheese.—Yvom. America cheese has come into the English market, made from skim-milk which has again been provided with fatty matter, generally emulsified margarine— hence the term “ margarine cheese,” or “ filled cheese ”•—a legitimate article if sold with full disclosure of its nature, but one which readily lends itself to fraud. Cases of cheese-poisoning have been recorded, and a highly poisonous substance, termed tyrotoxicon, has been extracted from cheese by Vaughan. Compounds of zinc and of lead have also been met with. Lard.—Between the years 1880 and 1890 a gigantic, fraudulent trade in adulterated lard was carried on from America. A great proportion of the American lard imported into England was found to consist of a mixture of more or less real lard, with cotton-seed oil and beef-stearine. Cotton-seed oil is one of the cheapest vegetable oils fit for human consumption; beef-stearine, the hard residue obtained in the manufacture of oleomargarine after the more fluid fat has been pressed out from the beef-fat. So skilfully were the mixtures made that for some years their very existence escaped notice, until in 1888 a bill introduced in the American Senate to stop the imposture directed general attention to the matter, and energetic measures by the food-officers quickly put a stop to it as affecting the United Kingdom. From the memorial presented to the U.S. Senate in support of the bill, it appeared that in about 1887 the annual production of lard in the States was estimated at 600 million pounds, of which more than 35 per cent, were adulterated. During the last seven or eight years compounds have been made containing no lard or only a faint trace of lard. These compounds were sold as “refined lard,” “pure refined lard,” “choice refined lard,” “choice refined family lard,”