Hygiene and public health / by B. Arthur Whitelegge.

  • Arthur Whitelegge
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Hygiene and public health / by B. Arthur Whitelegge. Source: Wellcome Collection.

    135/610 (page 123)
    Milk-Testing. and excluding air. In tliis way koumi.ss is pre- pared from the mare's milk, and kefir froni that of cows, goats, and sheep. Milk becomes sour much more rapidly in hot weather, or if the cow is diseased. If kept cool and in the dark, it absorbs oxygen and gives off carbonic acid, and the fat increases, owing to the slow conversion of a part of the casein. Milk exposed to sewer gas absorbs it readily, and soon decomposes : upon distil- lation it yields an offensive and poisonous liquid, causing headache and diarrhoea. Adulterations.—Addition of water and abstraction of cream are by far the most frequent frauds. Sodic carbonate, sodic chloride, borax, or salicylic acid are occasionally added, either as preservatives or in order to mislead the analyst, but the traditional chalk and calves' brains are now unknown. Skim milk or separ- ated milk is sometimes fortified by the addition of condensed milk. Addition of water lowers the specific gravity, the percentage of fat, solids not fat, and salts; it also makes the cream rise more readily to the surface. Abstraction of fat, by skimming or by the use of the separator, increases the specific gravity and the percentage of salts and solids not fat, but of course reduces the fat and therefore the yield of cream. The addition of condensed milk to skim milk may give an appearance of extreme richness, but the salts and solids not fat will be in excess. Preliminary Tests. I. Specific gravity of milk is measured by the lactometer, an instrument that is similar in construc- tion to an ordinary hydrometer, but graduated on the stem from about 1020 to 1040. The specific gravity averages about 1029 ; it is increased by skimming, and lowered by watering.