## 3 Results and Discussion
### Estimation of Microbial Growth Parameters and Shelf Life  
3.2.1. Microbial Growth Curves of Reference (CNT) Samples  
The presence of microorganisms in frankfurter sausages is the most critical indicator of their quality and safety. While it is common for food products to contain some level of microorganisms, it is essential to ensure that microbial counts remain within safe limits to protect human health [52]. Monitoring these levels helps to ensure the high quality of the sausages in order to simultaneously meet food safety standards and consumers' demands. In Figures 6a-d and 7a-d, the growth of the TVC and lactic acid bacteria in the CNT samples during storage at 4, 8, 12, and 18 \({}^{\circ}\)C, respectively, is illustrated. Figure 6: Growth of TVC in frankfurter-type sausages before HPP (CNT samples) during storage at (**a**) 4, (**b**) 8, (**c**) 12, and (**d**) 18 \({}^{\circ}\)C. Data points are means of four replicates, and error bars represent the corresponding standard deviation values. Solid lines represent the application of the Baranyi and Roberts microbial growth model, as described in Equation (1). The results of the microbiological analysis indicate that both the TVC and lactic acid bacteria increased with an increase in the storage temperature and time. The initial TVC for the CNT sausage samples was ca. 3.56 log CFU/g (Figure 6), indicating the initial good microbiological quality of all frankfurter-type sausages. It was observed that counts increased with an increase in both storage temperature and storage time, reaching 8.20-8.70 log CFU/g on the last day of storage at 4, 8, 12, and 18 \({}^{\circ}\)C. The growth of microorganisms increased with longer storage times because this provided sufficient time for microorganisms to multiply. For frankfurters, the limit of acceptability in terms of the TVC (8 log CFU/g) for the CNT samples was reached after 18, 11, 8, and 3 days of storage at 4, 8, 12, and 18 \({}^{\circ}\)C, respectively. Regarding the other spoilage microorganisms analyzed in this study, it was observed that the populations of _Pseudomonas_ spp. and _Enterobacteriaceae_ spp. remained below the detection threshold (<2 log CFU/g and <1 log CFU/g, respectively) throughout the storage of CNT samples at 4, 8, 12, and 18 \({}^{\circ}\)C. These findings are consistent with those reported by other researchers [53; 54]. It is well established that under aerobic storage conditions, _Pseudomonas_ spp. dominate at refrigeration temperatures and are a primary cause of spoilage in such products [54]. [PERSON] et al. [55] have also discussed the role of _Pseudomonas_ spp. in the aerobic spoilage of meat and how different packaging methods impact bacterial growth. Additionally, [PERSON] et al. [56] explained the way that vacuum packaging inhibits the growth of spoilage bacteria, including _Pseudomonas_ spp., in meat products. It is evident that the use of vacuum packaging in this study effectively inhibited the growth of these spoilage microorganisms. Figure 7: Growth of lactic acid bacteria in frankfurter-type sausages before HPP (CNT samples) during storage at (**a**) 4, (**b**) 8, (**c**) 12, and (**d**) 18 \({}^{\circ}\)C. Data points are means of four replicates, and error bars represent the corresponding standard deviation values. Solid lines represent the application of the Baranyi and Roberts microbial growth model, as described in Equation (1). Spoilage signs became apparent once the microbial load reached approximately 10\({}^{7}\) CFU/g, with significant sensory degradation occurring when TVCs reached 10\({}^{8}\) CFU/g. At this point, slime formation and acidification of the samples were evident. In addition, the population of lactic acid bacteria consistently reached 8 log CFU/g across all storage temperatures, following a growth profile similar to that of the TVC.