The on-farm separator
The first cream separator was invented in 1877 by the Swedish engineer Gustaf de Laval. It enabled farmers to separate their own milk and sell the cream to dairy factories, rather than taking milk to a skimming station to be separated. The major advantage was that only about 10% of the volume of milk had to be transported to the factory.
However, the change from skimming stations to on-farm separation was slow. As road transport improved, cream could be collected more regularly, and more milk was separated on farms. By 1918, 24,700 farms (71%) supplied cream to dairy factories. In the 1930s and 1940s a cream truck called at each farm every one or two days to collect cream cans and return empty ones. Cream cans were a fixture until 1951, when factories once again required whole milk, and the first large tanker collections began.
Milk fat and protein
When farmers separated the milk and sent cream to the local dairy factory, they were paid for the fat content, as this was the main ingredient in butter. However, it was later realised that the skim milk they were feeding to their pigs was high in protein. Today, skim milk is processed into a range of products and is more valuable to the farmer than milk fat.
Milking by hand
Owning more than three or four cows turned farming families into full-time dairy workers. It was time-consuming to care for cows and calves, do the milking, separate out the cream and drive it to the factory. The laborious business of hand milking created the demand for mechanical help.
The first machines
The first milking machines were built in Europe in the 1890s, and a Scottish model was trialled in Māngere, South Auckland, in 1893. Vacuum and pulsation was applied through four teat cups (called a cluster) attached to the cow’s udder. The milk was collected in buckets and emptied into vats. Later, these systems were connected up by small engines and electricity to a central machine. Milk flowed along pipes to a vat that delivered milk to the cream separator. When whole milk began to be collected, the milk was cooled in a heat exchanger then poured into cooling vats.
Once initial problems cleaning these machines had been overcome, they proved much more efficient than hand milking. They kept the milk enclosed and safe from contamination. Mechanical milking was the main reason for the increase in cow numbers and herd sizes from the beginning of the 20th century.