Part 86

König und Bömer, Zeitschrift für analytische Chemie, Band 34, S. 560.

This work, Vol. 2, pp. 297, 298.

Vid. op. cit. supra, p. 184.

Vid. op. cit. supra, p. 206.

This work, Vol. I, p. 450; Vol. 2, p. 226.

Zeitschrift für analytische Chemie, Band 34, S. 377.

König und Bömer, vid. op. cit. supra, S. 560.

Vid. op. cit. supra, S. 562.

Vid. op. cit. 53, p. 184.

Vid. op. cit. 57, S. 374.

Vid. op. cit. supra, S. 568.

From συρφετος.

PART SIXTH.

DAIRY PRODUCTS.

=426. Introductory.=—The importance of dairy products has led to the publication of a vast amount of literature relating thereto, and it seems almost a hopeless task to present even a typical abstract of the various analytical processes which have been proposed and used in their study. The general principles which have been developed in the preceding parts of this volume are applicable to the study of dairy products, and the analyst who is guided by them can intelligently examine the bodies specially considered in the present part. There have been developed, however, many valuable processes for the special examination of dairy products, which are of such a nature that they could not be properly discussed in the preceding pages. In the present part an effort will be made to present in a typical form the most important of these processes and to state the general principles on which they are based. This subject is naturally subdivided into three parts, viz., milk, butter and cheese. The milk sugar industry is not of sufficient importance to receive a special classification.

MILK.

=427. Composition of Milk.=—The composition of milk not only varies with the genus and species of the mammal from which it is derived, but also depends in a marked degree on idiosyncrasy.

Milk is a mixture containing water, proteids, fat, carbohydrates, organic and inorganic acids and mineral salts. There have also been observed in milk in minute quantities ammonia, urea, hypoxanthin, chyme, chyle, biliverdin, cholesterin, mucin, lecithin, kreatin, leucin and tyrosin. In the fermentation which milk undergoes in incipient decomposition there is sometimes developed from the proteid matter, as pointed out by Vaughn, a ptomaine, tyrotoxicon, which is a virulent poison. The presence of these last named bodies is of interest chiefly to the physiologist and pathologist and can receive no further attention here.

From a nutritive point of view, the important components of milk are the fats, proteids and sugar, but especially in the nourishment of the young the value of lime and phosphoric acid must be remembered. The mean composition of the most important milks, as determined by recent analyses, is given below:

Water. Sugar. Proteids. Fat. Ash. Per cent. Per cent. Per cent. Per cent. Per cent. Cow 86.90 4.80 3.60 4.00 0.70 Human 88.75 6.00 1.50 3.45 0.30 Goat 85.70 4.45 4.30 4.75 0.80 Ass 89.50 6.25 2.00 1.75 0.50 Mare 90.75 5.70 2.00 1.20 0.35 Sheep 80.80 4.90 6.55 6.85 0.90

The mean composition of milk, as given by Watts and König, is given in the following tables:

WATTS. Mineral Water. Solids. Proteids. Fats. Sugar. Salts. Woman 87.65 12.35 3.07 3.91 5.01 0.17 Ass 90.70 9.30 1.70 1.55 5.80 0.50 Cow 86.56 13.44 4.08 4.03 4.60 0.73 Goat 86.76 13.24 4.23 4.48 3.91 0.62 Sheep 83.31 16.69 5.73 6.05 3.96 0.68 Mare 82.84 17.16 1.64 6.87 8.65

KÖNIG. Casein and Milk Water. Fat. albumin. sugar. Ash. Woman 87.41 3.78 2.29 6.21 0.31 Mare 90.78 1.21 1.99 5.67 0.35 Ass 89.64 1.63 2.22 5.99 0.51 Cow 87.17 3.69 3.55 4.88 0.71

The average composition of 120,540 samples of cow milk, as determined by analysis, extending over a period of eleven years, was found by Vieth to be as follows:

Per cent. Total solids 12.9 Solids not fat 8.8 Fat 4.1

The quantity of solids and fat in milk is less after longer than after shorter periods between milkings.

The quantity of solids and fat in cow milk is less in the spring than in the autumn.

The chief organic acid naturally present in milk is citric, which exists probably in combination with lime.