MILK. 



671 



MILK (). The subject of tlie adulteration 

 of milk has been investigated with great care, 

 by M. Barruel of Paris. Although his observa- 

 tions are intended to apply only to the milk of that 

 city, yet there is little doubt that they will also 

 be found applicable in a greater or less degree to 

 all great towns. He sets out with stating that all 

 instruments for ascertaining the purity of milk, 

 which are calculated to attain this end by pointing 

 out differences in its density or specific gravity, are 

 inaccurate and useless. For, on the one band, pure 

 milk differs much in density according to the fod- 

 der used by the dairy-man for his cows, the buty- 

 raceous matter, which imparts lowness of density, 

 being made to preponderate by some sorts of food, 

 and the caseous part, which increases the density, 

 being made preponderate by other sorts. And, on 

 the other hand, although water, the ordinary sub- 

 stance with which milk is adulterated by the dealers 

 in the French capital, would alone cause a great 

 diminution of density, the dealers know very well 

 how to prevent that effect, and so render the 

 areometer useless. For this purpose, it is only 

 necessary to dissolve in the milk a little sugar- 

 candy, which is required at all events in order to 

 correct the flat taste imparted to milk by diluting 

 it with water. The result of M. Barruel's inquiries 

 on the adulteration of milk in Paris, is that no 

 positively noxious substance is ever to be found in 

 it ; that a common practice is to remove a con- 

 siderable portion of the cream, by allowing the 

 milk to stand for a limited time, and then to dilute 

 the remainder, or skimmed milk, with water, and 

 to give it the apparent qualities of new milk in one 

 or other of the manners now to be mentioned. The 

 opacity of the milk being much diminished by the 

 water, so that the milk acquired a bluish appear- 

 ance, it was at one time usual to correct this de- 

 fect, by previously mixing wheat-flour with the 

 water with which the milk was diluted. But this 

 adulteration was too obvious to the senses. Any 

 person even of indifferent delicacy of palate, could 

 detect the altered taste of the milk ; and besides, 

 after two hours' rest, the flour sank to the bottom, 

 restoring the translucent blueness of the milk, and 

 pointing out the nature of the fraud. To prevent 

 this inconvenience, the dealers boiled the flour in the 

 water before mixing it with milk ; and in this way 

 an opaque mixture was procured, which retained its 

 opacity on standing. As even with this addition 

 the fabricated liquid had a flat taste, sugar or sugar- 

 candy was dissolved in it, by which means the 

 peculiar sweetness of the milk was partly restored. 

 This adulteration, however, has become so easy of 

 detection by means of iodine, which renders the 

 mixture blue by its action on the fecula of the 

 flour, that M. Barruel believes that the fraud now 

 described is very little practised in the present day 

 at Paris. In Britain, where the municipalities take 

 no charge whatever of the purity of this most im- 

 portant article of food, it may be presumed that the 

 adulteration with flower, sugar, and water is com- 

 mon enough, as it is a simple and cheap mode of 

 accomplishing every purpose of the fraudulent 

 dealer. The best mode of proving the presence of 

 farinaceous matter in such mixture, is to heat the 

 milk with a little sulphuric acid, to coagulate the 

 casein, to filter the whey, and then to add to the 

 latter the tincture of iodine; upon which a fine 

 blue colour will be struck. Driven from this 

 species of adulteration, the Parisian dealers have 

 latterly resorted to another so ingenious, that M. 



Barruel conceives they could not have discovered 

 it without the aid of some scientific person. 

 The method is simple ; so cheap, that for tenpence 

 the opacity and colour of milk may be imparted 

 to thirty English pints of water, and so far secret 

 that no disagreeable taste is communicated. This 

 is nothing more than the employment of an 

 emulsion of almonds, for which some dealers, 

 more greedy and less cautious than the rest, 

 have substituted hemp-seed, which, however, is 

 apt to impart an acrid taste. By either of these 

 means the milk may be diluted to an indefinite ex- 

 tent; and the only corrective required is a little 

 sugar-candy to remove the flat taste. A peculiar 

 advantage possessed by this mode of adulteration 

 over every other, is, that the vegeto-animal matter, 

 or vegetable albumen of the emulsion by which 

 the oil of almond is held in suspension, is coagu- 

 lated, or curdled, like casein, by acids. The me- 

 thod recommended by M. Barruel for detecting the 

 fraud is founded on two circumstances, the greatly 

 inferior quantity of coagulum formed by acids in 

 the mixture of milk and almond emulsion, com- 

 pared with that formed in milk alone, and the 

 facility with which, by kneading the coagulum with 

 the fingers, oil may be squeezed out of the former, 

 while none exists in the latter. On examining 

 carefully four different specimens of pure milk, 

 procured from different quarters in Paris, he found 

 that 300 parts of each coagulated by heating them 

 with an equal volume of vinegar, gave each a quan- 

 tity of curd, which, when well drained, and equally 

 pressed between folds of bibulous paper, weighed 

 29 parts ; and that the same quantity of milk taken 

 from a cow in presence of a person sent to procure 

 it, gave 30 parts of curd. He then found, that 

 when the same milk was mixed with various pro- 

 portions of water, the quantity of curd was ex- 

 actly in the inverse ratio of the proportion of water 

 added. The water, therefore, did not prevent any 

 portion of the curd from being thrown down by 

 the usual modes of curdling the milk. He next 

 found, that, if a given quantity of sugar was added 

 to the mixture of milk and water, the quantity 

 added could be separated exactly by evaporating 

 the whey to the consistence of an extract, heating 

 this with alcohol, filtering the alcoholic solution, 

 and evaporating to dryness. He then also found 

 that, when equal parts of almond emulsion and 

 milk were mixed together, 300 parts of the mixture, 

 curdled by vinegar as above, gave 16 parts of curd ; 

 and that the same quantity of a mixture containing 

 two parts of emulsion to one of milk, gave only 

 10|th parts of curd. So that although, as was to 

 be expected, the adulteration with almond emulsion 

 did not lessen the quantity of curd to the same ex- 

 tent as adulteration with water only, yet the de- 

 crease was very great, and very nearly in the ratio 

 of the quantity of emulsion added. Lastly, on 

 placing pure curd on white paper, no oily matter 

 was thrown out ; but the curd procured from the 

 mixture of milk and almond emulsion, besides being 

 less firm than the former, gave out in twenty-four 

 or forty-eight hours a quantity of oil sufficient to 

 stain the paper. Another adulteration to which 

 milk is subjected in Paris, is with carbonate of 

 potass or soda. The object of this variety of adul- 

 teration is, in the hot summer months, to prevent 

 the milk from becoming sour and curdling, or to 

 break down the curd and correct acescency when 

 the milk has actually become spoiled. In this pro- 

 cess, acetate of potass or soda is formed. Neither 



