SUMMARY:Milk inoculated with 1 starter culture and immediately infected with small numbers of phage particles was afforded protection from phage attack for several hours if rennetted within 30 min of infection. The degree of protection was largely dependent upon the multiplication rate of the phage under test. When rennetting was delayed for 90 min after infection, protection was greatly reduced. The effect of early rennetting was to stimulate cell multiplication and retard the increase of phage. This retardation prolonged the period before equality between cell and phage numbers was reached. Even after equality was reached, acid production continued for some hours in milk that had received early addition of rennet.
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