Two farms, using direct-to-can milking, were used to compare utensil cleaning with hot detergent solution followed by hypochlorite on one farm and steam on the other, with immersion of the complete milking equipment in 5% caustic soda between milkings. Control and caustic treatments were used alternately for periods of 8 weeks for a total of 8 months.
Bacteriological tests made at weekly intervals on fresh milk and milk aged for 24 hr. at 22° C. showed little difference between the control methods, which involved brushing the milk contact surfaces, and the caustic soda method where there is no brushing.
The majority of micro-organisms in the bulk milk came from the udder and the utensils contributed little to the milk. It appeared that where utensils are satisfactorily cleaned, milking technique will be the factor which mainly affects keeping quality.
A study of the predominant flora revealed that milk from equipment cleaned by immersion in caustic soda had a simpler flora (mainly micrococci) than the control treatments.