## 3 Results and Discussion
### L. monocytogenes Behavior in DCH during Storage after HPP: Growth/No Growth
#### 3.2.1 L. monocytogenes  
No-Growth Conditions: Survival and Inactivation during Storage No growth of _L. monocytogenes_ was predicted to occur (_I_ = 0) in products with an \(a_{w}\) < 0.95 (Table 2), which agreed with the observed results, where survival (no microbiology) relevant change, trials 33 and 48) or inactivation of _L. monocytogenes_ was observed during the storage of DCH (trials 34-47 and 49-51; Table 2; Figure 4).  
Trials involving HPP at 750-852 MPa had a strong lethal effect (_L. monocytogenes_ was not detected), not allowing subsequent monitoring (trials 36-38, 44-47, 50-51, 51-55; Table 2; Figure 4). For pressure levels < 600 MPa, the concentration of _L. monocytogenes_ after the HPP and its subsequent behavior was affected by the pressure level applied as well as the DCH's characteristics (\(a_{w}\) value and fat content). In DCH with an \(a_{w}\) of 0.87 pressurized at 600 MPa (Trial 33; Table 2; Figure 4a) the levels of _L. monocytogenes_ after HPP were variable and close to the quantification level, with no detection of the pathogen in 12.5% of the samples along the storage. Overall, no relevant change (survival without inactivation) can be associated with these trial conditions. The survival of _L. monocytogenes_ could be the consequence of the piezo-protection effect exerted by low \(a_{w}\) on the lethality of the pathogen by HPP. Indeed, this would result in fewer injured _L. monocytogenes_ cells due to its role in protein stabilization, which prevents protein denaturation and cell death during HPP [26], and which in turn could contribute to keeping the pathogen viability after HPP.  
_L. monocytogenes_ was also able to survive without any significant change during the storage of DCH with an \(a_{w}\) of 0.94 pressurized at 300 MPa (Trial 48; Table 2; Figure 4c). Compared to other trials, in this case, the survival of the pathogen could be favored by either (i) the high \(a_{w}\) value (0.94), since the application of a similar pressure level (347 MPa) in DCH with a lower \(a_{w}\) (0.919) resulted in the inactivation of the pathogen during the storage (Trial 41; Table 2; Figure 4b), and/or (ii) the lower pressure compared with trial 49 (at 450 MPa, \(a_{w}\) of 0.94) in which inactivation was observed. These hypotheses would be supported by [PERSON] et al. [24], showing that the levels of _L. monocytogenes_ after the pressurization of smoked DCH (pH of 5.87 and \(a_{w}\) of 0.93) at 600 MPa for 5 min were low and progressively inactivated to limits below the quantification limit (0 log cfu/g) after the storage of the DCH at 4 \({}^{\circ}\)C for 38 days and afterwards at 8 \({}^{\circ}\)C for 18 days.  
In DCH with an \(a_{w}\) of 0.919, _L. monocytogenes_ decreased during the storage of DCH after HPP irrespective of the pressure level (from 347 to 600 MPa; trials 41, 42 and 43; Table 2; Figure 4b). Therefore, even if the pressure increase enhances the immediate lethality of _L. monocytogenes_ during HPP, it has no effect on the inactivation of the pathogen during the subsequent storage after HPP in DCH with an \(a_{w}\) of 0.919.  
Regarding the impact of fat, an increase from 18 to 42% did not significantly affect the _L. monocytogenes_ lethality during HPP nor its subsequent inactivation after HPP in DCH with an \(a_{w}\) of 0.89 (trials 34-35; Table 2; Figure 4a). Contrarily, for DCH with an \(a_{w}\) of 0.95, a higher content of fat enhanced the lethality of _L. monocytogenes_ by HPP and significantly reduced the inactivation of the pathogen during the subsequent storage (trials 52-53; Table 2; Figure 4d).