Modeling of Listeria monocytogenes inactivation by combined high-pressure and mild-temperature treatments in model soup

• Published in: European food research & technology Vol. 242; no. 2; pp. 279 - 287
• Main Authors: Ates, Mehmet Baris, Rode, Tone Mari, Skipnes, Dagbjørn, Lekang, Odd-Ivar
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2016; Springer Nature B.V
• Subjects: Agriculture; Analytical Chemistry; Biotechnology; Chemistry; Chemistry and Materials Science; control methods; equations; Food; food industry; Food preservation; food research; Food safety; Food Science; Forestry; Heat; high pressure treatment; Inactivation; inoculum; Listeria; Listeria monocytogenes; meat; Milk; Original Paper; ready-to-eat foods; Recovery (Medical); soups; Studies; synergism; Synergistic effect; Temperature; Temperature effects; Norway; Inactivation model; HPP; Recovery; Mild heat; Injury
• ISSN: 1438-2377; 1438-2385
• DOI: 10.1007/s00217-015-2539-2

High-pressure processing (HPP) in combination with mild heat is known to have a synergistic effect on bacterial inactivation in broth, milk and meat. This synergistic effect has, however, not been documented for a ready-to-eat (RTE) soup. In this study, Listeria monocytogenes inactivation in a model RTE soup under combined high-pressure and mild-temperature (P/T) treatments was modeled according to a central composite design. The model was significant (P < 0.0001) with a satisfactory predictability (R ₐdⱼ ² = 0.95). Effects of P/T on L. monocytogenes inactivation were assessed by solving the deduced quadratic equation and analyzing its contour plot. More than 6-log inactivation of Listeria was possible at combined P/T ranges of 525 MPa/40 °C to 600 MPa/25 °C within 5 min. This was in accordance with FDA and EC guidance on refrigerated RTE foods that a treatment intensity equivalent to 6-log reduction of L. monocytogenes would be required as a listericidal control measure. Moreover, 600 MPa treatments at ≥45 °C for 5 min resulted in no L. monocytogenes recovery in the model soup during 3 weeks at 4 and 8 °C when the inoculum size was 10³ or 10⁵ CFU/ml. Results clearly indicated that use of mild temperatures in combination with HPP can induce a more complete inactivation, hence reducing the microbial recovery in foods after HPP. Experimental results and the fitted model in this study may be utilized as a comparison to other inactivation models and for determining test conditions for process safety assessments on similar refrigerated products in food industry.