# High Pressure and Pasteurization Effects on Dairy Cream +
## 3 Results and Discussion  
### Microbial Analysis  
Regarding the first batch experiments, TAP, LAB, and ENT were quantified before (initial) and right after (day zero) thermal or HPP, and also on days 5, 9, 18, 33, and 51 under refrigeration (4 \({}^{\circ}\)C) (Figure 1). As represented in Figure 1, TAP, LAB, and ENT counts of thermally pasteurized cream samples decreased to below the detection limit (<1.00 log CFU/mL), maintaining low counts until the ninth day of storage. From the 18 th day onwards, microbial growth was observed for all microorganisms, except for ENT, which remained undetected. By the 51 st  
Figure 1: Microbial growth of (**a**) TAP, (**b**) LAB, and (**c**) ENT on initial raw cream after heat (75 °C, 15 s) treatment and after pressure treatment under 450 MPa and 600 MPa during 5 min (first batch). Analyses were made on the initial cream and right after processing (**b**) and after 5 (**c**), 9 (**d**), 18 (**e**), 33 (**f**), and 51 (**g**) days of storage at 4 °C. Bars with * and # represent microbial loads below the detection limit (lower than 1.00 log CFU/mL) and above 6.00 log CFU/mL, respectively. Different letters denote significant differences (\(p\leq 0.05\)) between storage days for each condition (A,B) and treatment conditions for each storage day (a,b). day, TAP and LAB counts surpassed 6.00 log CFU/mL, and, therefore, no further analyses were performed for the thermally pasteurized cream. Right after processing at 450 MPa for 5 min, TAP loads observed were similar to those of raw dairy cream, while for samples processed at 600 MPa for 5 min, a very small (not statistically significant) decrease was observed. For ENT, regardless of the treatment, its counts were reduced to below 1.00 log CFU/mL and kept constant throughout storage. These results are in agreement with [PERSON] et al. (2010), who reported a similar barosensitivity of ENT when human milk was pressurized at 400, 500, and 600 MPa for 5 min at 12 \({}^{\circ}\)C [19]. [PERSON] et al. (2014), working with starter-free fresh cheees, also observed that after HPP (500 MPa, 5 min, 16 \({}^{\circ}\)C), ENT was not able to recover during all the cold storage period (21 days) [20]. From the 18 th day onwards, both TAP and LAB counts were above 6.00 log CFU/mL; thus, samples treated at 450 MPa for 5 min (450/5) were considered spoiled. Samples processed at 600 MPa for 5 min (600/5) resulted in a slower recovery of TAP and LAB under refrigeration in comparison to those processed at 450/5, with TAP counts only increasing (\(p\leq 0.05\)) after the 51 st day (Figure 1). This demonstrates the efficiency of HPP at 600 MPa to injure microorganisms, taking them additional time to recover and develop compared to the thermal pasteurization process. To evaluate the influence of pressurization time, a second study was performed, and a new fresh cream batch was processed at 600 MPa for 15 min (600/15) instead of 5. Since in the first study, ENT exhibited high sensitivity to both high pressure and pasteurization treatments, the effect of 600/15 was evaluated only for TAP and LAB. In addition to endogenous microorganisms, the effect of HPP (600/5 and 600/15) on inoculated _L. innocua_ and _E. coli_ was also evaluated. The 600/15 condition significantly reduced (\(p\leq 0.05\)) TAP and LAB counts by about 1.4- and 1.8-fold, respectively, compared to the initial raw cream counts (Figure 2). Figure 2: \(Cont.\)  
By the 28 th day of storage, TAP counts on thermally pasteurized samples increased to values above 6.00 log CFU/mL, while those treated by HPP (600/15) presented counts of 4.53 \(\pm\) 0.11 log CFU/mL, evidencing the efficacy of HPP in inhibiting long-term microbial development and extending shelf life. Regarding LAB, a significant increase (\(p\leq\) 0.05) throughout storage was observed. Concerning inoculated microorganisms, 600/5 and 600/15 treatments were able to significantly reduce (\(p\leq\) 0.05) _E. coli_ counts compared to the initial inoculated load (Figure 2). By the 10 th day, _E.