Microbial inactivation by pressure-shift freezing: effects on smoked salmon mince inoculated with Pseudomonas fluorescens, Micrococcus luteus and Listeria innocua |
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Authors: | Laetitia Picart Eliane Dumay Joseph-Pierre Guiraud |
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Affiliation: | a Unité de Biochimie-Technologie Alimentaires, Université des Sciences et Techniques du Languedoc, Montpellier CDX 5 F-34095, Franceb UMR Ingénierie des Agro-Polymères et Technologies Emergentes, Université des Sciences et Techniques du Languedoc, Montpellier CDX 5 F-34095, Francec UMR Ingénierie des Réactions Biologiques et Bioproductions, Université des Sciences et Techniques du Languedoc, Montpellier CDX 5 F-34095, France |
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Abstract: | Smoked salmon mince inoculated simultaneously with Listeria innocua, Micrococcus luteus and Pseudomonas fluorescens was subjected to different pressure-temperature conditions. Control freeze-thaw at 0.1 MPa with storage at −15°C or −40°C for 0-5 days did not induce microbial inactivation. Control pressurisation at 207 MPa for 23 min at 20°C (initial sample temperature) with fast (3 s) pressure release had no significant effect on Gram+bacteria while P. fluorescens underwent a 2.8 log cycle reduction. Pressurisation at 207 MPa for 23 min at −3°C (without ice crystal formation) enhanced microbial reduction to 3.8 log cycles for P. fluorescens and to about 0.5 log cycle for Gram+bacteria. “Pressure-shift nucleation” (PSN) from 207 MPa and −21°C (i.e. cooling at 207 MPa for 23 min followed by pressure release in 3 s) caused 1.2, 1.4 and 4.3 log cycle reductions of L. innocua, M. luteus and P. fluorescens, respectively. A reduction of 1.7 log cycle was observed for L. innocua and M. luteus (4.6 log cycle for P. fluorescens) when salmon mince was subjected to pressure-shift freezing (PSF) (i.e. PSN from 207 MPa and −21°C as above followed by further freezing to −25°C at 0.1 MPa). PSF with pressure release in 18 min enhanced reduction to 2 and 2.5 log cycles for L. innocua and M. luteus, respectively. |
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Keywords: | High hydrostatic pressure Ice nucleation Pressure-shift freezing Fish mince Seafood |
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