The basic principles of phage control in commercial plants have been known since the early 1940s and the pioneering work of Dr Hugh Whitehead and his colleagues in New Zealand. The review by Whitehead and Hunter (1945)* on the measures that were being used in New Zealand to control slow acid production due to phage infection is still of relevance to factory managers today. The 1945 review focused on whey as the vehicle for phage transmission, and on work designed to break the cycle of phage infection. Even in 1945 they recognised the challenge of keeping phage concentrations low in the environment, the need for special facilities to produce phage-free bulk starter in a potentially phage-infected environment, the possibility of raw milk being contaminated with phage because the cans, tankers today, carrying whey, and also used to carry raw milk, could contaminate raw milk. They were also aware that whey separators and 'splashes' of whey produced aerosols and that these would enable phage to become airborne. Off course they were not aware of lysogency and the possibility of phage arising from the starter or lactococci in raw milk.

Modern methods for controlling phage problems in cheesemaking include:-

1. Use of starters containing phage-unrelated or phage-insensitive strains.

2. Production of 'phage-free' bulk starter
 • Aseptic propagation systems
 • Use of phage-inhibitory media
 • Segregation of starter room and cheese process equipment CIP-systems
 • Removal of deposits on bulk starter vessels
 • Ensuring the ''head space' is minimised in bulk starter vessels and sterilised.

3. Minimising the concentration of phage in processing plants
 • Culture rotations
 • Air conditioning
 • Aerosol generation/fumigation
 • Cleaning/chlorination of vats between refills
 • Good factory design. Location of whey storage tanks, whey handling systems.

3. Other measures

 • Use of DVI/DVS cultures
 • Inspection of jackets/agitators for pin holing
 • Early renneting.

Written by Michael Mullan