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Browsing by Author "Geornaras, Ifigenia, advisor"

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    Efficacy of antimicrobial treatments against Salmonella enterica on pork and Campylobacter jejuni on poultry
    (Colorado State University. Libraries, 2020) González Sánchez, Sara Victoria, author; Belk, Keith E., advisor; Geornaras, Ifigenia, advisor; Delmore, Robert J., committee member; Weir, Tiffany L., committee member
    Two studies were conducted to evaluate efficacy of antimicrobial treatments against Salmonella enterica on pork and Campylobacter jejuni on poultry. The first study was conducted to (i) evaluate decontamination efficacy of six chemical treatments when applied to pork jowls inoculated with Salmonella enterica and (ii) determine the antimicrobial efficacy of the test solutions against a high and low inoculum level of Salmonella. Chilled pork jowls were cut into 10 × 5 × 1 cm portions and were surface-inoculated on the skin side with a mixture of six S. enterica serotype strains of swine origin. The inoculation levels targeted were 6 to 7 log CFU/cm2 (high) and 3 to 4 log CFU/cm2 (low). Following inoculation, samples were left untreated (control) or were treated by spray application (10 s, 18 to 19 psi, 1.0 gpm flow rate) with water, a proprietary blend of sulfuric acid and sodium sulfate (SSS, pH 1.2), formic acid (1.5%), peroxyacetic acid (PAA, 400 ppm), PAA (400 ppm) acidified with acetic acid (1.5%), PAA (400 ppm) acidified with formic acid (1.5%), or PAA (400 ppm) acidified with SSS (pH 1.2). Samples were analyzed for inoculated Salmonella counts immediately after treatment application (0 h) and after 24 h of refrigerated (4°C) storage. Overall, all seven spray treatments were effective (P < 0.05) at reducing the high and low Salmonella inoculation levels. At the high inoculum level (6.2 log CFU/cm2), pathogen counts ranged from 5.4 (water; 0.8 log CFU/cm2 reduction) to 4.3 (PAA acidified with SSS; 1.9 log CFU/cm2 reduction) log CFU/cm2 for samples analyzed immediately after spray treatment. Salmonella counts obtained at the 0-h sampling time for treated samples inoculated at the low inoculum level (3.5 log CFU/cm2) ranged from 2.8 (water; 0.7 log CFU/cm2 reduction) to 1.8 (PAA acidified with SSS; 1.7 log CFU/cm2 reduction) log CFU/cm2. Thus, regardless of inoculum concentration, similar reductions of Salmonella populations were obtained immediately following treatment application (0 h). For the high inoculation level, Salmonella counts of samples analyzed after 24 h of refrigerated storage were, in general, similar (P ≥ 0.05) to the counts of the corresponding treatment at 0 h. However, for the low inoculation level, pathogen counts of jowls treated with SSS, formic acid, or PAA acidified with formic acid, and held at 4°C for 24 h, were 0.6 log CFU/cm2 lower (P < 0.05) than the 0-h counts of the corresponding treatment. Regardless of inoculation level and sampling time, no (P ≥ 0.05) differences in efficacy were obtained between PAA on its own and any of the acidified PAA treatments evaluated. The second study was conducted to (i) evaluate decontamination efficacy of five chemical treatments when applied to chicken wings inoculated with Campylobacter jejuni and (ii) determine antimicrobial efficacy of the treatments as a result of applying test solutions by immersion or spraying. Skin-on chicken wings were surface-inoculated with a six-strain mixture of C. jejuni of poultry origin. The target inoculation level was 3 to 4 log CFU/mL of wing rinsate. Following inoculation, samples were left untreated (control) or were treated by immersion (500 mL solution per wing; 5 s) or spray application (10 to 12 psi; 4 s) with water, SSS (pH 1.2), formic acid (1.5%), PAA (550 ppm), PAA (550 ppm) acidified with SSS (pH 1.2), or PAA (550 ppm) acidified with formic acid (1.5%). Samples were analyzed for C. jejuni counts immediately after treatment application (0 h) and following 24 h of storage (4°C). All five acid treatments evaluated in this study were effective (P < 0.05) at reducing the initial inoculated (3.9 log CFU/mL) C. jejuni populations on chicken wings, regardless of the antimicrobial treatment application method. Pathogen counts for samples spray-treated with one of the chemical solutions and analyzed immediately (0 h) after treatment ranged from 3.4 (SSS; 0.5 log CFU/mL reduction) to 2.7 (PAA acidified with formic acid; 1.2 log CFU/mL reduction) log CFU/mL. When the chemical treatments were applied by immersion, C. jejuni counts of 2.2 (SSS; 1.7 log CFU/mL reduction) to 1.7 (PAA, and PAA acidified with SSS; 2.2 log CFU/mL reduction) log CFU/mL were obtained for wings analyzed at the 0-h sampling time. The PAA and acidified PAA treatments were equally (P ≥ 0.05) effective at reducing initial C. jejuni populations, regardless of treatment application method. However, following refrigerated storage, samples treated with SSS- or formic acid-acidified PAA had lower (P < 0.05) pathogen counts than those that had been treated with the non-acidified PAA treatment. Overall, findings of the two studies should be useful to the pork and poultry industries as they consider new interventions against Salmonella and Campylobacter contamination on pork and chicken parts, respectively.
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    ItemOpen Access
    Processes to improve storage shelf-life and palatability of beef
    (Colorado State University. Libraries, 2023) González Sánchez, Sara Victoria, author; Nair, Mahesh N., advisor; Geornaras, Ifigenia, advisor; Morgan, J. Brad, committee member; Gutierrez-Rodriguez, Eduardo, committee member
    Three studies were conducted to evaluate processes to improve the storage shelf-life and palatability of beef. The first two studies evaluated the effects on retail shelf-life and palatability characteristics of beef following Suspended Fresh® storage. Suspended Fresh® (SF) is a patented, proprietary, trademarked process that allows the storage of beef muscles at temperatures at or slightly above their freezing point to slow down microbiological spoilage while maintaining the product's fresh status. These studies evaluated the impact of 60, 75, or 90 d of storage in SF (-2.7±0.3°C) on the retail shelf-life and palatability characteristics of steaks derived from inside rounds (IR), bone-in ribeyes (RE), and striploins (SL) from 10 (n=10) upper two-thirds Choice beef carcasses. Two steaks fabricated from each subprimal were vacuum-packaged, wet-aged for 21 d (3°C), and frozen (-20°C) for Warner-Bratzler shear force (WBSF) and sensory analyses. These steaks served as the control with regard to storage condition and time. The remainder of each subprimal was fabricated into three portions, and after vacuum packaging, were randomly allocated to an SF storage time of 60, 75, or 90 d. After each storage time, five steaks were fabricated from the subprimal pieces, overwrapped, and placed in a retail display case (3°C) under continuous fluorescent light for 7 d. Another two steaks were vacuum-packaged and stored at -20°C until WBSF and consumer sensory evaluations. Consumers (N=238) evaluated each sample for juiciness, tenderness, flavor liking, and overall liking. Instrumental and trained visual color were evaluated daily during retail display, and aerobic bacterial populations (APC), lactic acid bacteria, and Pseudomonas spp. were enumerated on days 0, 2, 4, and 7. Data were analyzed in R using a factorial design for the microbial counts or a split-plot for the rest of the analyses. Least-squares means were separated using a significance level of α=0.05. For all cuts, initial redness (a* values) of SF60 steaks were lower (P < 0.05) than SF75 and SF90 steaks. In general, irrespective of SF storage time or retail display day, trained panelists did not detect differences in lean color and discoloration of steaks. For all cuts, the APC of SF60 steaks on days 0, 2, and 4 of retail display were lower (P < 0.05) than those of SF75 and SF90 samples. The WBSF values decreased (P < 0.05) with increased storage time for all the cuts. Similarly, the consumer tenderness rating scores of IR and SL generally increased with the SF storage time. However, storage time did not influence (P ≥ 0.05) the juiciness, flavor, and overall liking of any cuts. The results of this study suggest it would be feasible to extend the storage time of beef while preserving or improving the sensory quality when held at optimal conditions above the freezing temperature. The third study was conducted to evaluate the effects of different temperature and time treatment combinations (1A: 56.1°C and 71 min; 1B: 56.1°C and 150 min; 1C: 56.1°C and 240 min; 2A: 61.7°C and 8 min; 2B: 61.7°C and 150 min; 2C: 61.7°C and 240 min) of sous vide cooking on the palatability of beef biceps femoris. Beef biceps femoris were sliced into 1.6-cm steaks, vacuum packaged as 4.5 kg bags, and randomly assigned to one of the six treatments with 16 packages (n=16) per treatment. Cooked and chilled packages were weighed, and then the weight of the meat was taken to measure cooking loss. Weighed samples were divided into two halves: one was left non-marinated, and the other was assigned to marination. Two 1.6-cm non-marinated steaks were randomly selected and cut in half to measure the internal cooked color. Additionally, non-marinated and marinated steaks were randomly selected for WBSF and sensory analysis by a trained panel. Data were analyzed using a complete randomized design in R with a significance level of α=0.05. The cooking loss of samples increased as the temperature and dwell time combinations increased (P < 0.05). Internal redness of steaks decreased (P < 0.05) with increased temperature and dwell time. The only major difference in WBSF and the trained sensory panel results was between treatment 1C (56.1°C and 240 min) and 2A (61.7°C and 8 min), where 1C samples had lower WBSF values and higher perceived tenderness scores than 2A samples. These results suggest that biceps femoris samples can be cooked at conditions examined in this study with minimal impact on palatability, allowing producers more flexibility with cooking time to optimize production time and energy while reducing cooking loss. Overall, the findings of these studies should be useful to the beef industry as they consider strategies for improving the storage shelf-life and palatability of beef.