AUTHOR=Liang Dong , Zhang Liang , Wang Xu , Wang Pan , Liao Xiaojun , Wu Xiaomeng , Chen Fang , Hu Xiaosong 

TITLE=Building of Pressure-Assisted Ultra-High Temperature System and Its Inactivation of Bacterial Spores

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01275

DOI=10.3389/fmicb.2019.01275

ISSN=1664-302X

ABSTRACT=<p>The pressure-assisted ultra-high temperature (PAUHT) system was built by using soybean oil as pressure-transmitting medium, and the multiple regression equation of soybean oil temperature change (Δ<italic>T<sub>P</sub></italic>) during pressurization as a function of initial temperature (<italic>T<sub>i</sub></italic>) and set pressure (<italic>P</italic>) was developed: Δ<italic>T<sub>P</sub></italic> = -13.45 + 0.46 <italic>T<sub>i</sub></italic> + 0.0799 P - 0.0037 <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>T</mml:mi><mml:mi>i</mml:mi><mml:mn>2</mml:mn></mml:msubsup></mml:mrow></mml:math></inline-formula> - 2.83 × 10<sup>-5</sup> P<sup>2</sup>. The fitted model indicated that the temperature of the system would achieve ≥121°C at 600 MPa when the initial temperature of soybean oil was ≥84°C. The PAUHT system could effectively inactivate spores of <italic>Bacillus subtilis</italic> 168 and <italic>Clostridium sporogenes</italic> PA3679 (less than 1 min). Treatment of 600 MPa and 121°C with no holding time resulted in a 6.75 log reductions of <italic>B. subtilis</italic> 168 spores, while treatment of 700 MPa and 121°C with pressure holding time of 20 s achieved more than 5 log reductions of <italic>C. sporogenes</italic> PA3679 spores. By comparing the PAUHT treatment with high pressure or thermal treatment alone, and also studying the effect of compression on spore inactivation during PAUHT treatment, the inactivation mechanism was further discussed and could be concluded as follows: both <italic>B. subtilis</italic> 168 and <italic>C. sporogenes</italic> PA3679 spores were triggered to germinate firstly by high pressure, which was enhanced by increased temperature, then the germinated spores were inactivated by heat.</p>