**3. Results**

### *3.1. Hot Water Wash*

The main effect of the feed type had no statistical significance throughout any of the sampling dates of the study. There was no significant difference (*p* > 0.25) on the bacterial counts observed between grain and grass-fed carcasses in the study; therefore, the main effect of the feed type was removed to better visualize differences due to the washing and chilling types' main effects and their interaction. The hot water wash carcass intervention significantly reduced (*p* < 0.05) APC on the carcass surface (Figure 1). However, no washed treatments presented lower aerobic plate counts than the washed counterparts. After a 24 h chilling period, there was an increase in PSY counts and a stalled growth of APC. Psychrotrophic bacteria were not significantly reduced by the hot water wash intervention

(Figure 2) and had growth after a 24 h chilling period. EB, EC, and CO counts were below the detection limit (<0.25 CFU/cm2) in most samples taken at each sampling point assessed.

**Figure 1.** Aerobic plate counts of the beef carcass surface before and after the hot water wash intervention and 24 h chilling period. The horizontal line within the box plot represents the median. The box upper and lower limits represent the interquartile range, and the bars represent the 1.5xInterquartile Range. a–e Box plots with different letters are significantly different (*p* < 0.05).

**Figure 2.** Psychrotroph counts of the beef carcass surface before and after the hot water wash intervention and 24 h chilling period. The horizontal line within the box plot represents the median. The box upper and lower limits represent the interquartile range, and the bars represent the 1.5xInterquartile Range. a,b Box plots with different letters are significantly different (*p* < 0.05).

### *3.2. Extended Shelf Life of Striploins*

The statistical analysis indicates a significant effect of time for all the indicator microorganism loads assessed, as expected. Because of this, the statistical comparison between treatments was conducted within a per sampling date basis, rather than over the time of storage. The loads of each indicator microorganism evaluated was compared between treatments within each sampling date. On sampling day 0, no significant differences among treatments could be observed in any of the five microbial indicators quantified (*p* > 0.05) and the indicator bacteria were mostly below the detection limit (Table 1). Even though no immediate effect could be observed from spray and dry chilling at day 0, in the long term, and throughout the additional sampling periods during refrigerated storage, significantly lower (*p* < 0.05) concentrations of APC, PSY, and EB can be observed in the dry chilling treatments (Figures 3–5) when compared to their spray-chilled counterparts.


**Table 1.** Summary table of microbial indicator microorganism counts in striploins before and after the intervention, chilling method, and evaluation at day 0, 45, 70, and 135 of refrigerated storage.

> 1 Standard Error. \* Below detection limit (<0.25 CFU/cm2).

**Figure 3.** Aerobic plate counts of striploins at day 0, 45, 70, and 135 of refrigerated storage. The horizontal line within the box plot represents the median. The box upper and lower limits represent the interquartile range, and the bars represent the 1.5xInterquartile Range. D = No Wash Dry chill, S = No Wash Spray chill, WD = Wash Dry chill, WS = Wash Spray chill. a–c Box plots with different letters within each sampling date are significantly different (*p* < 0.05).

No significant differences on coliform counts between treatments at each sampling date could be found throughout the extended shelf life section of the study; however, significant growth over time was observed. *E. coli* counts on striploins were mostly below the detection limit (<0.25 CFU/cm2) at the plant and throughout the extended shelf life. Thus, no significant growth of *E. coli* over time was observed. Furthermore, significant growth of EB was observed only after 45 days of wet aging, encountering significant differences between treatments during long-term storage.

Even though the hot water wash's main effect was not statistically significant throughout the extended shelf life study, a trend (0.05 < *p* < 0.15) of an increase in microbes quantified could be observed whenever the carcasses underwent the hot water wash intervention compared to their dry chilling counterparts. The highest microbial concentrations were consistently observed on the washed and spray-chilled striploins treatment and the lowest microbial loads were consistently observed in the no-washed dry-chilled striploins.

Although significant interaction between the main effects was not observed statistically, a trend in the interaction was observed (0.05 < *p* < 0.15).

**Figure 4.** Psychrotroph counts of striploins at day 0, 45, 70, and 135 of refrigerated storage. The horizontal line within the box plot represents the median. The box upper and lower limits represent the interquartile range, and the bars represent the 1.5xInterquartile Range. D = No Wash Dry chill, S = No Wash Spray chill, WD = Wash Dry chill, WS = Wash Spray chill. a–c Box plots with different letters within each sampling date are significantly different (*p* < 0.05).

**Figure 5.** Enterobacteriaceae counts of striploins at day 0, 45, 70, and 135 of refrigerated storage. The horizontal line within the box plot represents the median. The box upper and lower limits represent the interquartile range, and the bars represent the 1.5xInterquartile Range. D = No Wash Dry chill, S = No Wash Spray chill, WD = Wash Dry chill, WS = Wash Spray chill. a–c Box plots with different letters within each sampling date are significantly different (*p* < 0.05).

EB counts were significantly different between treatments after long-term storage (*p* < 0.05). Dry chilling methods had their medians at 0 log CFU/cm2, indicating a low concentration of EB even after 135 days of refrigerated storage. Moreover, the no-wash dry chilling treatment combination had the lowest concentration of EB across all times evaluated. The treatment's significant differences after prolonged refrigeration times become evident from day 45 of long-term refrigeration storage.
