Effect of water activity on inactivation of Listeria monocytogenes and lactate dehydrogenase during high pressure processing

Changes in Barotolerance, Thermotolerance, and Cellular Morphology throughout the Life Cycle of Listeria monocytogenes

“…We speculate that the enhanced barotolerance in the long-term-survival phase seen in the present study may be due to cytoplasmic condensation and subsequent lowered water activity in coccoid cells. Lowered water activity was previously shown to dramatically enhance the barotolerance of L. monocytogenes (19).…”

Microbiological food safety assessment of high hydrostatic pressure processing: A review

“…Carboxylic acids normally employed as food preservatives have a high degree of dissociation under conditions of high pressure, and it is the non-dissociated form which has an antimicrobial effect. Lower values of water activity (a w ) increase microbial resistance (Black, Huppertz, et al, 2007;Black, Setlow, et al, 2007;Hayman, Kouassi, et al, 2008;Patterson, 2005). This phenomenon is observed both in synthetic models and food.…”

Modeling the protective effect of a w and fat content on the high pressure resistance of Listeria monocytogenes in dry-cured ham

“…Similarly to run 15, an average of −2.9 Log inactivation for L. monocytogenes CTC1034 (the same strain used in the present work) inoculated on sliced Iberian dry-cured ham (a w = 0.88; 33.3% fat) treated at 600 MPa was previously reported (Hereu, BoverCid, et al, 2012). An extreme demonstration of the protective effect of low a w values occurred with the pressurization of lyophilized cells of L. monocytogenes, for which no inactivation at all was observed (Hayman et al, 2008). The piezoprotection given by low a w can be related to the stabilization of proteins (particularly enzymes), reducing its pressure-induced denaturation in biological systems (Georget et al, 2015).…”

“…For instance, while acidity usually favor HPinactivation of microorganisms, the presence of proteins and sugars has been reported to act as protective agents on microbial cells (Black, Huppertz, Fitzgerald, & Kelly, 2007;Gao, Ju, & Wu, 2007;García-Graells, Masschalck, & Michiels, 1999). Similarly, high fat and/or low water activity (a w ) values have been shown to decrease the antimicrobial effectiveness of HP treatments (Erkmen & Dogan, 2004b;Hayman, Kouassi, Anantheswaran, Floros, & Knabel, 2008;Hereu, Dalgaard, Garriga, Aymerich, & Bover-Cid, 2012).…”