Abstract
The potential of two previously developed pressure–temperature–time indicators (pTTIs) to detect temperature differences during high pressure (HP) processing was assessed. In a first theoretical approach, numerical integration of pressure, temperature-profiles and kinetic data of inactivation of the pTTIs, Bacillus amyloliquefaciens α-amylase and Bacillus subtilis α-amylase, was applied to translate hypothetical temperature profiles under pressure into indicator read-outs. This resulted in the definition of the application window with regard to initial temperature of the pressure medium (equal to the high pressure wall), the pressure level, build-up rate and holding time. Both indicators showed great potential for use in HP pasteurization processing. Secondly, in an experimental part, the temperature uniformity in a horizontally oriented, industrial scale HP equipment was mapped for the first time, using these indicators. Differences in indicator read-outs were obtained in the radial plane of the HP vessel, and based on the kinetic data of the pTTIs, attributed to temperature differences. Of course, this temperature non-uniformity will only result in process non-uniformity if the temperature dependency of the kinetics of the target attribute (safety, quality) is sufficiently temperature sensitive in the studied pressure, temperature-range.
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