Effect of High Hydrostatic Pressure on Aeromonas hydrophila AH 191 Growth in Milk

Authors

  • Ricardo Durães-Carvalho,

    1. Authors Durães-Carvalho, Souza, and Bonafe are with Dept. de Bioquímica, authors Martins and Yano are with Dept. de Microbiologia e Imunologia, and author Sprogis is with Centro de Microscopia Eletrônica, Inst. de Biologia, Univ. Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, CEP 13083–970, Brazil. Author Bispo is with Lab. de Fenômenos de Transporte, Dept. de Tecnologia (DTEC), Faculdade de Engenharia de Alimentos, Univ. Estadual de Feira de Santana (UEFS), CP 252/294, Feira de Santana, BA, CEP 44036–900, Brazil. Direct inquiries to author Bonafe (E-mail: bonafe@unicamp.br).
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  • Ancelmo R. Souza,

    1. Authors Durães-Carvalho, Souza, and Bonafe are with Dept. de Bioquímica, authors Martins and Yano are with Dept. de Microbiologia e Imunologia, and author Sprogis is with Centro de Microscopia Eletrônica, Inst. de Biologia, Univ. Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, CEP 13083–970, Brazil. Author Bispo is with Lab. de Fenômenos de Transporte, Dept. de Tecnologia (DTEC), Faculdade de Engenharia de Alimentos, Univ. Estadual de Feira de Santana (UEFS), CP 252/294, Feira de Santana, BA, CEP 44036–900, Brazil. Direct inquiries to author Bonafe (E-mail: bonafe@unicamp.br).
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  • Luciano M. Martins,

    1. Authors Durães-Carvalho, Souza, and Bonafe are with Dept. de Bioquímica, authors Martins and Yano are with Dept. de Microbiologia e Imunologia, and author Sprogis is with Centro de Microscopia Eletrônica, Inst. de Biologia, Univ. Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, CEP 13083–970, Brazil. Author Bispo is with Lab. de Fenômenos de Transporte, Dept. de Tecnologia (DTEC), Faculdade de Engenharia de Alimentos, Univ. Estadual de Feira de Santana (UEFS), CP 252/294, Feira de Santana, BA, CEP 44036–900, Brazil. Direct inquiries to author Bonafe (E-mail: bonafe@unicamp.br).
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  • Adriane C. S. Sprogis,

    1. Authors Durães-Carvalho, Souza, and Bonafe are with Dept. de Bioquímica, authors Martins and Yano are with Dept. de Microbiologia e Imunologia, and author Sprogis is with Centro de Microscopia Eletrônica, Inst. de Biologia, Univ. Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, CEP 13083–970, Brazil. Author Bispo is with Lab. de Fenômenos de Transporte, Dept. de Tecnologia (DTEC), Faculdade de Engenharia de Alimentos, Univ. Estadual de Feira de Santana (UEFS), CP 252/294, Feira de Santana, BA, CEP 44036–900, Brazil. Direct inquiries to author Bonafe (E-mail: bonafe@unicamp.br).
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  • Jose A. C. Bispo,

    1. Authors Durães-Carvalho, Souza, and Bonafe are with Dept. de Bioquímica, authors Martins and Yano are with Dept. de Microbiologia e Imunologia, and author Sprogis is with Centro de Microscopia Eletrônica, Inst. de Biologia, Univ. Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, CEP 13083–970, Brazil. Author Bispo is with Lab. de Fenômenos de Transporte, Dept. de Tecnologia (DTEC), Faculdade de Engenharia de Alimentos, Univ. Estadual de Feira de Santana (UEFS), CP 252/294, Feira de Santana, BA, CEP 44036–900, Brazil. Direct inquiries to author Bonafe (E-mail: bonafe@unicamp.br).
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  • Carlos F. S. Bonafe,

    1. Authors Durães-Carvalho, Souza, and Bonafe are with Dept. de Bioquímica, authors Martins and Yano are with Dept. de Microbiologia e Imunologia, and author Sprogis is with Centro de Microscopia Eletrônica, Inst. de Biologia, Univ. Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, CEP 13083–970, Brazil. Author Bispo is with Lab. de Fenômenos de Transporte, Dept. de Tecnologia (DTEC), Faculdade de Engenharia de Alimentos, Univ. Estadual de Feira de Santana (UEFS), CP 252/294, Feira de Santana, BA, CEP 44036–900, Brazil. Direct inquiries to author Bonafe (E-mail: bonafe@unicamp.br).
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  • Tomomasa Yano

    1. Authors Durães-Carvalho, Souza, and Bonafe are with Dept. de Bioquímica, authors Martins and Yano are with Dept. de Microbiologia e Imunologia, and author Sprogis is with Centro de Microscopia Eletrônica, Inst. de Biologia, Univ. Estadual de Campinas (UNICAMP), CP 6109, Campinas, SP, CEP 13083–970, Brazil. Author Bispo is with Lab. de Fenômenos de Transporte, Dept. de Tecnologia (DTEC), Faculdade de Engenharia de Alimentos, Univ. Estadual de Feira de Santana (UEFS), CP 252/294, Feira de Santana, BA, CEP 44036–900, Brazil. Direct inquiries to author Bonafe (E-mail: bonafe@unicamp.br).
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Abstract

Abstract:  Exposure to high pressure is an efficient method of bacterial inactivation that is particularly important for reducing the microbial load present in foods. In this study, we examined the high pressure inactivation of Aeromonas hydrophila AH 191, a virulent strain that produces aerolysin, a cytotoxic, enterotoxic, and hemolytic toxin. High pressure treatment (250 MPa for 30 min at 25 °C in 0.1 M PBS, pH 7.4) of A. hydrophila grown in milk reduced bacterial viability by at least 9 orders of magnitude. Under these conditions, the enterotoxic, hemolytic, and cytotoxic activities of A. hydrophila culture supernatants were unaltered. These results indicate the need for caution in the use of high pressure for food processing since although truly toxigenic bacteria may be inactivated, their toxins may not be, thus posing a risk to human health. At higher pressure (350 MPa) the inactivation of bacteria was much more effective. Scanning electron microscopy showed a significant decrease in the number of bacteria after higher pressurization (350 MPa for 1 h) and transmission electron microscopy showed irregular shaped bacteria, suggestive of important cell wall and membrane damage, and cytoplasm condensation.

Practical Application:  High pressure inactivates Aeromonas hydrophila efficiently but is enhanced when combined with moderate temperature (40 °C). The biological activities of toxins from this bacterium are unaltered under these conditions.

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