MILK CONTAINERS

Wairarapa Times-Age, 7 June 1940, Page 2

MILK CONTAINERS

EFFECT ON CONTENTS. Milk is a colloid. That is, its solids are in a very finely divided state, approaching, but not quite reaching that of a perfect solution. Because of this, fresh milk displays some peculiar characteristics. For example, it is both acid and alkaline, having the power to turn red litmus to blue and blue litmus to red. Fresh milk contains a certain amount of apparent real acidity (about one-tenth of one per cent), as it comes from the cow —-and this acidity increases as the milk ages. Acids react with metals to form metallic salts, the same as they react with alkalis to form neutral salts. Certain metals are more resistant to the action of acids than other metals, and because of the fact that tin resists the action of the acidiy in milk, or cream most dairy equipment is coated with tin, or is made from nickel or is coated with glass. The tinned or other surfaces with which the milk or cream comes in contact must always be thoroughly clean and sterile in order to prevent bacterial contamination. Consequently, the cleaning of dairy equipment presents a serious and important problem to the industry, because the cleaning operation must be particularly thorough and yet it must not have any harmful or corroding effect upon the surface of the equipment cleaned.