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Influence of pH,water activity and temperature on the inactivation of Escherichia coli and Saccharomyces cerevisiae by pulsed electric fields
Affiliation:1. Instituto de Agroquímica y Tecnología de Alimentos (IATA-CSIC), Carrer del Catedràtic Agustín Escardino Benlloch, 7, 46980 Paterna, València, Spain;2. LAQV, REQUIMTE/DGAOT, Faculdade de Ciências. Universidade do Porto, Campus Agrário de Vairão, Rua Padre Armando Quintas, 7, 4485-661, Vairão, Vila do Conde, Portugal;3. GreenUP/CITAB-UP, Campus Agrário de Vairão, Rua Padre Armando Quintas, 7, 4485-661 Vairão, Vila do Conde, Portugal;1. Department of Food Hygiene and Technology and Institute of Food Science and Technology, University of León, 24071 León, Spain;2. Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Universidad de Zaragoza, 50013 Zaragoza, Spain
Abstract:The aim of this study was to examine the influence of pH, water activity (aw) and temperature on the killing effect of pulsed electric fields (PEF). Escherichia coli and Saccharomyces cerevisiae suspended in a model media were subjected to 20 pulses with 4 μs duration in a continuous PEF system, during which the effects of pH (4.0–7.0), aw (1.00–0.94) and inlet temperature (10°C and 30°C) could easily be studied. Electrical field strengths were set to 25 kV/cm for S. cerevisiae and 30 kV/cm for E. coli and the highest outlet temperature was monitored to 44°C. A synergy of low pH values, high temperatures and PEF processing was observed. A drop in pH value from 7.0 to 4.0 resulted in the reduction of E. coli by four additional log units, whereas for S. cerevisiae, the pH effect was less pronounced. Lowering aw seems to protect both E. coli and S. cerevisiae from PEF processing.
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