Published online by Cambridge University Press: 01 June 2009
1. Measurements of hardness and ‘free-oil’ content of samples of butter from cream held at various temperatures before churning were made before and after storage. Hardness was determined by the sectility method, while free-oil content was estimated from the weight of oil exuding from thin slices of butter sandwiched between filter-papers and held at 64–4° F. (18° C).
2. Butter from cream held at 60° F. and churned at 45° F. was much softer and contained more free oil than butter from cream held and churned at 45° F.
3. If the cream was precooled to 45° F. before being held at 60° F. the butter was very slightly softer than that from cream held at 60° F. without precooling, but the difference disappeared after storage. It contained rather less free oil, but the softening point of the oil was lower. Fat losses in churning which were high where cream was held at 60° F. were reduced almost to normal when cream was precooled before being held at 60° F.
4. Cream slowly cooled to 45° F. yielded butter which was softer and contained more free oil than that from cream cooled rapidly to 45° F. and held at that temperature. The butter, however, was not so soft as that from cream held at 60° F.
5. Butter from cream held at a temperature below that at which it was to be churned did not differ significantly in hardness or free-oil content from that produced from cream held at the churning temperature.
6. Present commercial methods of cream treatment in New Zealand (rapid cooling to churning temperature and holding at that temperature) give butter of almost maximum hardness for the type of fat involved at each stage of the season.
7. More uniform consistency of butter throughout the season could be achieved only by reducing the hardness of the firmer butter and not by increasing the firmness of the ofter butter.