METHODS OF ASSESSING THE SPORICIDAL EFFICIENCY OF AN ULTRA‐HIGH‐TEMPERATURE MILK STERILIZING PLANT. II. EXPERIMENTS WITH SUSPENSIONS OF SPORES IN MILK

Abstract

SUMMARY: The sporicidal efficiency of an ultra‐high‐temperature (UHT) milk processing plant has been tested using spores of a strain of Bacillus subtilis in milk. With the inoculum and volume of milk adjusted to obtain a countable number of survivors by a conventional dilution counting method, a temperature of 130·5° with the minimum time setting of the plant was found necessary to give a destruction of 99·99999%. This temperature was lower than that found previously (135°) for spores suspended in water and evidence is produced to support the suggestion that UHT milk may be inhibitory to the germination and/or subsequent growth of heated spores.