Relationship between Sublethal Injury and Microbial Inactivation by the Combination of High Hydrostatic Pressure and Citral or tert -Butyl Hydroquinone

Abstract

The aim was to investigate (i) the occurrence of sublethal injury in Listeria monocytogenes, Escherichia coli, and Saccharomyces cerevisiae after high hydrostatic pressure (HHP) treatment as a function of the treatment medium pH and composition and (ii) the relationship between the occurrence of sublethal injury and the inactivating effect of a combination of HHP and two antimicrobial compounds, tert-butyl hydroquinone (TBHQ) and citral. The three microorganisms showed a high proportion of sublethally injured cells (up to 99.99% of the surviving population) after HHP. In E. coli and L. monocytogenes, the extent of inactivation and sublethal injury depended on the pH and the composition of the treatment medium, whereas in S. cerevisiae, inactivation and sublethal injury were independent of medium pH or composition under the conditions tested. TBHQ alone was not lethal to E. coli or L. monocytogenes but acted synergistically with HHP and 24-h refrigeration, resulting in a viability decrease of >5 log 10 cycles of both organisms. The antimicrobial effect of citral depended on the microorganism and the treatment medium pH. Acting alone for 24 h under refrigeration, 1,000 ppm of citral caused a reduction of 5 log 10 cycles of E. coli at pH 7.0 and almost 3 log 10 cycles of L. monocytogenes at pH 4.0. The combination of citral and HHP also showed a synergistic effect. Our results have confirmed that the detection of sublethal injury after HHP may contribute to the identification of those treatment conditions under which HHP may act synergistically with other preserving processes.

Sublethal injury and virulence changes in Listeria monocytogenes and Listeria innocua treated with antimicrobials carvacrol and citral

“…The same happened when the cells were held for up to 6 h in the presence of citral. These results are similar to those obtained by Somolinos et al (2008) for another microorganism. They detected a higher proportion of sublethal damage in E. coli cultures when cells were held for 5 h in the presence of 200 mL/L of citral, which agrees with our results of 4e6 h. Fig.…”

Inactivation by 405 ± 5 nm light emitting diode on Escherichia coli O157:H7, Salmonella Typhimurium, and Shigella sonnei under refrigerated condition might be due to the loss of membrane integrity

“…It is known that Gram-negative bacteria have a lipopolysaccharide (LPS) in the outer membrane, which provides a permeability barrier to hydrophobic molecules such as bile salts in the external Typhimurium; 2, S. Typhimurium without LED illumination for 7.5 h; 3, LEDilluminated S. Typhimurium for 7.5 h; 4, healthy E. coli O157:H7; 5, E. coli O157:H7 without LED illumination for 7.5 h; 6, LED-illuminated E. coli O157:H7 for 7.5 h; 7, healthy S. sonnei; 8, S. sonnei without LED illumination for 7.5 h; 9, LED-illuminated S. sonnei for 7.5 h. environment. Moreover, the cytoplasmic membrane is responsible for the regulation of osmotic pressure (Ait-Ouazzou et al, 2012;Jasson et al, 2007;Somolinos et al, 2008). Thus, these results indicate that both outer and cytoplasmic membranes of bacteria might become damaged or suffer loss of their functionality during 405 ± 5 nm LED illumination.…”

“…The increased bacterial sensitivity to bile salts and NaCl implies the losses of outer membrane function as a permeability barrier to (A) hydrophobic compounds and to (B) osmotic functionality of cytoplasmic membrane, respectively (Ait-Ouazzou, Mañas, Cond on, Pag an, & García-Gonzalo, 2012; Jasson, Uyttendaele, Rajkovic, & Debevere, 2007;Somolinos, García, Pag an, & Mackey, 2008).…”

Bactericidal effects of high hydrostatic pressure treatment singly or in combination with natural antimicrobials on Staphylococcus aureus in rice pudding

“…These results indicate a very low contribution of these two bacteriocins in the inactivation of staphylococci by combined treatments in pudding. The activity of bacteriocins can be potentiated by essential oils (Gálvez et al, 2006), yet there are few reports on the combination of essential oils and HHP treatments (Evrendilek & Balasubramaniam, 2011;Somolinos et al, 2008;Vurma et al, 2006), none of them dealing with S. aureus. This could be an interesting field for future research in order to improve the effects of HHP treatments and also to decrease the impact of essential oils on the food organoleptic properties.…”

“…The presence of fat, proteins, minerals and sugars serves as a protector and increases microbial resistance to pressure (Black, Huppertz, Kelly, & Fitzgerald, 2007). The efficacy of HHP treatments can improve in combination with other antimicrobial substances such as bacteriocins, lysozyme, or essential oils (Corbo et al, 2009;Evrendilek & Balasubramaniam, 2011;García-Graells, Van Opstal, Vanmuysen, & Michiels, 2003;Masschalck, Van Houdt, & Michiels, 2001;Somolinos, García, Pagán, & Mackey, 2008;Vurma, Chung, Shellhammer, Turek, & Yousef, 2006). Nisin is widely used as a licensed food preservative (Thomas, Clarkson, & Delves-Broughton, 2000).…”