Thermal death kinetics of <i>Bacillus stearothermophilus</i> spores at ultra high temperatures III. Relationship between data from capillary tube experiments and from UHT sterilizers

Abstract

Summary Thermal death data were obtained for B. stearothermophilus spores heated in (a) a laboratory scale, direct heating UHT plant and (b) a larger scale direct heating UHT plant. These were compared with the corrected data from experiments in which spores of the same batch were heated in capillary tubes. Temperature coefficients ( Q 10 values) for inactivation of spores in UHT plants were higher than those for spores in capillary tubes but agreement was closer when spores were suspended in water than in milk. For aqueous spore suspensions, the discrepancy between plants and capillaries was least for the laboratory scale plant. the divergence always became greater at lower temperatures and the D values were coincident at 145°C. Possible reasons for these various effects are discussed.