Higher Grade Cream

Sun (Auckland), Volume II, Issue 614, 16 March 1929, Page 27

Higher Grade Cream

CLEANLINESS ESSENTIAL

Control of Bacteria

CONSIDERABLE indignation followed the remarks of a dairyman at a recent meeting of suppliers to a Northern butter factory when he stated that much of the trouble making for low-grade cream came from insufficient regard to cleanliness in the sheds. No doubt, more attention could bo paid to cleanliness by many dairy factory suppliers. Many, in fact, do not realise the important part bacteria, encouraged by insufficiently clean conditions, plays in making for lowgrade cream and milk.

Harmful bacteria in cream and i juilk—the direct cause of inferior | quality and deterioration in dairy pro- j ducts —may be combated only by! thorough cleanliness. To under stand I the great importance of eliminating | inimical bacteria the dairyman should hare a knowledge of their habits and the correct method of control. One drop of milk may contain millions of bacteria, not necessarily of the harmful kind, but of a nature which renders milk a perishable product. ilacteria require three conditions for their growth and development-—food, moisture, and warmth. The temperature at which these minute organisms i Ur ive best is between 90deg. and 100 deg. Pahr. Their activities practically cease at 32deg. and 150 deg. Milk is recognised as one of the most favourable materials for the growth of bacteria, and it is for this reason that dairy farmers should exercise the strictest care in the handling of their product. Bacteria multiply by the simple process of division. Some types, known as sporing types, produce an off-shoot from the adult type, llns form of bacteria is very resistent to adverse conditions. Although ordinary pasteurisation will destroy all adult forms, the spores are not affected, and they will begin work as goon as favourable conditions are set up. This constitutes the main difference between pasteurisation and sterilisation. Sterilisation is accomplished only by three separate boilings of half an hour each, by which all organism is destroyed. Several methods of efficient control may be exercised by dairymen. The udder of a healthy cow is practically free from bacteria with the exception of the teat canal, which becomes exposed to bacterial influences by pressure, as when the cow is lying down. If the first portion of the milk contained in the teat is stripped out and discarded, the remaining milk is, to a considerable extent, kept pure. Very little loss is sustained by this method, and the quality of the milk, from a bacterial point of view, is greatly improved. During milking bacteria may find access to the milk in many ways. When unclean methods are followed conditions for their development are most favourable and contamination is inevitable. A dirty cowyard, unwashed teats and udders, a neglected milking machine, utensils that have not been properly washed and scalded, and the dirty hands of a milker, are among the

primary causes of the contamination j of milk. The quality of the cream j will suffer through passing through an i unclean separator. A very objection-) able form of fermentation is causedj by dust from a dirty cowyard. The j sediment that will accumulate In the j pipes of milking machines will create an active and harmful form of I, bacteria. The control of bacteria falls under three main headings—the removal, as far as possible, of all contaminating influences by thorough cleanliness; a clean cowyard and milking-shed, together with clean hands and udders;

and the reducing of the temperature of milk or cream as quickly as possible.

All bacteria contained in milk are not harmful. The type which use the milk sugar as food are known as lactic acid bacteria, and they produce a clean fermentation. Use is made of these bacteria in the ripening process of milk for cheesemaking and cream for butter-making. They are introduced into milk or cream in the form of a commercial starter, and they have the effect of producing a nutty flavour. Churning is facilitated, and in cheese manufacture the peptonisation of the milk solids into a more digestible form is assisted. When these bacteria gain the ascendancy in the early stages of manufacture the growth and development of the harmful types Is made more difficult.