Randall K. Phebus

Evaluation of a steam pasteurization process in a commercial beef processing facility

The effectiveness of a steam pasteurization process for reducing naturally occurring bacterial populations on freshly slaughtered beef sides was evaluated in a large commercial facility. Over a period of 10 days, 140 randomly chosen beef sides were microbiologically analyzed. Each side was sampled immediately before, immediately after, and 24 h after steam pasteurization treatment. Total aerobic bacteria (APC), Escherichia coli (generic), coliform, and Enterobacteriaceae populations were enumerated. The process significantly (P ≤ 0.01) reduced mean APCs from 2.19 log CFU/cm2 before treatment to 0.84 log CFU/cm2 immediately after and 0.94 log CFU/cm2 24 h after treatment. Before pasteurization (8 s steam exposure), 16.4% of carcasses were positive for generic E. coli (level of 0.60 to 1.53 log CFU/cm2), 37.9% were positive for coliforms (level of 0.60 to 2.26 log CFU/cm2), and 46.4% were positive for Enterobacteriaceae (level of 0.60 to 2.25 log CFU/cm2). After pasteurization, 0% of carcasses were positive for E. coli , 1.4% were positive for coliforms (level of 0.60 to 1.53 log CFU/cm2), and 2.9% were positive for Enterobacteriaceae (level of 0.60 to 1.99 log CFU/cm2). Of the 140 carcasses evaluated, one carcass was positive for Salmonella spp. before treatment (0.7% incidence rate); all carcasses were negative after steam treatment. This study indicates that steam pasteurization is very effective in a commercial setting for reducing overall bacterial populations on freshly slaughtered beef carcasses. The system may effectively serve as an important critical control point for HACCP systems at the slaughter phase of beef processing. In conjunction with other antimicrobial interventions (mandated by USDA to achieve zero tolerance standards for visible contamination) and good manufacturing practices, this process can play an important role in reducing the risk of pathogenic bacteria in raw meat and meat products.

Steam pasteurization of commercially slaughtered beef carcasses: Evaluation of bacterial populations at five anatomical locations

A steam pasteurization process (patent pending) has been shown to effectively reduce pathogenic bacterial populations on beef tissue and to significantly reduce naturally occurring bacterial populations on commercially slaughtered beef carcasses. The objective of this study was to determine the effectiveness of the steam pasteurization treatment for reducing bacterial populations at several anatomical locations on commerically slaughtered carcasses. Before and after pasteurization treatment (82.2 degrees C, 6.5-s exposure time), a sterile sponge was used to sample 300 cm2 at one of five locations (inside round, loin, midline, brisket, or neck). Eighty carcasses (40 before treatment and 40 after treatment) were sampled per anatomical location over 2 processing days. Before treatment, aerobic plate counts (APCs) were found to be highest (P < or = 0.01) at the midline (4.5 log10 CFU/100 cm2), intermediate at the inside round, brisket, and neck (ca. 3.8 log10 CFU/100 cm2), and lowest at the loin (3.4 log10 CFU/100 cm2). After treatment, APCs at all locations were reduced significantly (P < or = 0.01). The inside round, loin, and brisket had the lowest (P < or = 0.01) APCs (ca. 2.6 log10 CFU/100 cm2), whereas the midline and neck had APCs of 3.1 and 3.3 log10 CFU/100 cm2, respectively. The lower reduction in APCs at the neck area indicated that the treatment may not be as effective there, possibly because of the design of the pasteurization equipment. Generic Escherichia coli populations were low at all locations before treatment, with populations on 32% of all carcasses sampled being less than the detection limit of the study (5.0 CFU/100 cm2). After treatment, E. coli populations were significantly lower (P < or = 0.01) than populations before treatment and 85% of all carcasses sampled had E. coli populations below the detection limit. The maximum E. coli population detected after treatment was 25 CFU/100 cm2. For enteric bacterial populations, no differences were observed in the effectiveness of the treatment among the five carcass locations.

Translocation of Surface-Inoculated Escherichia coli O157:H7 into Beef Subprimals following Blade Tenderization†‡

In phase I, beef subprimals were inoculated on the lean side with ca. 0.5 to 3.5 log CFU/g of a rifampin-resistant (rifr) cocktail of Escherichia coli O157:H7 and passed once, lean side up, through a mechanical blade tenderizer. Inoculated subprimals that were not tenderized served as controls. Ten core samples were removed from each subprimal and cut into six consecutive segments: segments 1 to 4 comprised the top 4 cm and segments 5 and 6 the deepest 4 cm. Levels of E. coli O157:H7 recovered from segment 1 of control subprimals when inoculated with ca. 0.5, 1.5, 2.5, or 3.5 log CFU/g were 0.6, 1.46, 2.5, and 3.19 log CFU/g, respectively. Following tenderization, pathogen levels recovered from segment 1 inoculated with 0.5 to 3.5 log CFU/g were 0.22, 1.06, 2.04, and 2.7 log CFU/g, respectively. Levels recovered in segment 2 were 7- to 34-fold lower than levels recovered from segment 1. Next, in phase II, the translocation of ca. 4 log CFU of the pathogen per g was assessed for lean-side-inoculated subprimals passed either once (LS) or twice (LD) through the tenderizer and for fat-side-inoculated subprimals passed either once (FS) or twice (FD) through the tenderizer. Levels in segment 1 for LS, LD, FS, and FD tenderized subprimals were 3.63, 3.52, 2.85, and 3.55 log CFU/g, respectively. The levels recovered in segment 2 were 14- to 50-fold lower than levels recovered in segment 1 for LS, LD, FS, and FD subprimals. Thus, blade tenderization transfers E. coli O157:H7 primarily into the topmost 1 cm, but also into the deeper tissues of beef subprimals.

Control of Clostridium perfringens germination and outgrowth by buffered sodium citrate during chilling of roast beef and injected pork

Inhibition of the germination and outgrowth of Clostridium perfringens by buffered sodium citrate (Ional) and buffered sodium citrate supplemented with sodium diacetate (Ional Plus) during the abusive chilling of roast beef and injected pork was evaluated. Beef top rounds or pork loins were injected with a brine containing NaCl, potato starch, and potassium tetrapyrophosphate to yield final in-product concentrations of 0.85, 0.25, and 0.20%, respectively. Products were ground and mixed with Ional or Ional Plus at 0, 0.5, 1.0, and 2.0%. Each product was mixed with a three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.5 log10 spores per g. Chilling of roast beef from 54.4 to 7.2 degrees C resulted in C. perfringens population increases of 1.51 and 5.27 log10 CFU/g for 18- and 21-h exponential chill rates, respectively, while chilling of injected pork resulted in increases of 3.70 and 4.41 log10 CFU/g. The incorporation of Ional into the roast beef formulation resulted in C. perfringens population reductions of 0.98, 1.87, and 2.47 log10 CFU/g with 0.5, 1.0, and 2.0% Ional, respectively, over 18 h of chilling, while > or = 1.0% Ional Plus was required to achieve similar reductions (reductions of 0.91 and 2.07 log10 CFU/g were obtained with 1.0 and 2.0% Ional Plus, respectively). An Ional or Ional Plus concentration of > or = 1.0% was required to reduce C. perfringens populations in roast beef or injected pork chilled from 54.4 to 7.2 degrees C in 21 h. Cooling times for roast beef or injected pork products after heat processing can be extended to 21 h through the incorporation of > or = 1.0% Ional or Ional Plus into the formulation to reduce the potential risk of C. perfringens germination and outgrowth.

Effectiveness of trimming and/or washing on microbiological quality of beef carcasses

Beef carcass sides (n = 48) were selected randomly on three different days in a commercial processing facility and microbiologically analyzed before being moved to the cooler. Four types of samples were obtained per side from the inside round area: no trim and no wash (NTNW); trim, but no wash (TNW); trim and wash (TW), and no trim but wash (NTW). A flame-sterilized knife, forceps, and scalpel were used for each trimming treatment and sampling. Significant differences (P < 0.05) were observed in mean aerobic plate counts (APCs) between treatments. The greatest reduction in APC (log10 colony forming units [CFU] per cm2) was observed in TNW samples followed by TW and NTW, with the corresponding mean APC reductions relative to NTNW being 3.0, 0.9, and 0.3, respectively, indicating that trimming can be an effective control point in reducing bacterial contamination in the slaughter process. Although TNW samples, had the lowest counts, samples from the same location after wash (TW) had counts 2 log cycles higher than TNW samples. These results indicate that washing spreads contamination to adjacent carcass sites. However, washing of carcasses was effective in lowering microbial populations relative to the NTNW treatment. Escherichia coli and coliform counts in all samples were low (0.03 to 0.4 log10 CFU/cm2); however, the mean E. coli or coliform count in NTNW samples was higher (P < 0.05) than those in the rest of the treatments.

Validation of a Traditional Italian-Style Salami Manufacturing Process for Control of Salmonella and Listeria monocytogenes†

Italian-style salami batter (formulated with pork shoulder) was inoculated with ca. 7.0 log CFU/g of either Salmonella or Listeria monocytogenes. Salami links (55-mm cellulose casings) were fermented at 30 degrees C for 24, 40, or 72 h and then dried to target moisture/protein ratios (MPRs) of 1.9:1 or 1.4:1. Links were sampled after fermentation (24, 40, and 72 h) and after combined fermentation-drying treatments (MPRs of 1.9:1 and 1.4:1 for all fermentation periods), and microbiological and proximate analyses were performed at each sampling. Pathogen populations were enumerated by direct plating on selective agar and by an injured-cell recovery method. When enumerated by the injured-cell recovery method, Salmonella populations were reduced by 1.2 to 2.1 log CFU/g after fermentation alone (24 to 72 h) and by 2.4 to 3.4 log CFU/g when fermentation was followed by drying. Drying to an MPR of 1.4:1 was no more effective than drying to an MPR of 1.9:1 (P > 0.05). When enumerated directly on selective media, Salmonella populations were reduced from 1.6 to 2.4 log CFU/g and from 3.6 to 4.5 log CFU/g for fermentation alone and fermentation followed by drying, respectively. L. monocytogenes populations were reduced by <1.0 log CFU/g following all fermentation and combined fermentation-drying treatments, regardless of the enumeration method. These results suggest that the Italian-style salami manufacturing process evaluated does not adequately reduce high pathogen loads. Processors may thus need to consider supplemental measures, such as raw material specifications and a final heating step, to enhance the lethality of the overall manufacturing process.

Survival of Campylobacter jejuni in modified atmosphere packaged Turkey roll

Survival of Campylobacter jejuni , inoculated into turkey roll slices and stored under seven different atmospheric mixtures, was determined. Turkey roll samples were stored at 4°C for 18 d and at 21°C for 48 h. The effects of various atmospheric mixtures on aerobic, psychrotrophic, and lactic acid bacterial populations were also determined throughout storage. Campylobacter jejuni was inactivated under all atmospheric gas mixtures tested throughout storage. Increasing CO2 concentration inside the package from 0% to 100% CO2 resulted in a lower rate of inactivation of C. jejuni at both storage temperatures. Increases in CO2 concentrations provided greater inhibition of aerobic and psychrotrophic populations as compared to low CO2 levels. The effect of CO2 on survival of C. jejuni and growth rate of aerobic, psychrotrophic, and lactic acid bacteria was more pronounced at 4°C. Campylobacter s were isolated from inoculated turkey roll held under all atmospheres by enrichment procedures on the 18th day and 48th hour of storage at 4 and 21°C, respectively, with an initial population of log 6.0 Campylobacter s/g. However, no Campylobacter s were isolated by 18 d of storage at 4°C by direct plating.

Effectiveness of a laboratory-scale vertical tower static chamber steam pasteurization unit against Escherichia coli O157 :H7, Salmonella Typhimurium, and Listeria innocua on prerigor beef tissue

A laboratory-scale vertical tower steam pasteurization unit was evaluated to determine the antimicrobial effectiveness of different exposure times (0, 3, 6, 12, and 15 s) and steam chamber temperatures (82.2, 87.8, 93.3, and 98.9 degrees C) against pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria innocua) inoculated onto prerigor beef tissue. Samples were collected and microbiologically analyzed immediately before and after steam treatment to quantify the effectiveness of each time-temperature combination. The 0-s exposure at all chamber temperatures (cold water spray only, no steam treatment) was the experimental control and provided < or = 0.3 log CFU/cm2 reductions. Chamber temperatures of 82.2 and 87.8 degrees C were ineffective (P > 0.05) at all exposure times. At 93.3 degrees C, significant reductions (> 1.0 log CFU/cm2) were observed at exposure times of > or = 6 s, with 15 s providing approximately 1 log cycle greater reductions than 12 s of exposure. The 98.9 degrees C treatment was consistently the most effective, with exposure times of > or = 9 s resulting in >3.5 log CFU/cm2 reductions for all pathogens.

Time and temperature of stretching as critical control points for Listeria monocytogenes during production of mozzarella cheese.

Different heating times and temperatures commonly used during curd stretching were investigated to determine their effects on the viability of Listeria monocytogenes in mozzarella cheese. Pasteurized whole milk was inoculated with two levels of L. monocytogenes (7 and 3 log CFU/g) and coagulated with citric acid and rennet. The curd was stretched at 55, 66, and 77 degrees C for 1, 3, and 5 min. Results indicated that the majority of L. monocytogenes cells remained in the cheese curds at both inoculum levels. Stretching at 66 degrees C for 3 min reduced the number of L. monocytogenes by 5 log units, whereas stretching at 55 degrees C had a minimal effect. Stretching at 77 degrees C resulted in the complete demise of L. monocytogenes cells (from 7.6 log CFU/g to < 1.0 log CFU/g) in 1 min. If the stretching temperature partially reduced microbial counts, bring (4 degrees C for 12 h) usually had a lethal effect on the remaining microorganisms, but was less effective than the stretching temperature. These results show that stretching curd at 66 degrees C for 5 min or 77 degrees C for 1 min can effectively control L. monocytogenes during the production of mozzarella cheese.

Gluconic acid as a fresh beef decontaminant

Effectiveness of 0, 1.5 and 3.0% gluconic acid (G) and/or 0 and 1.5% lactic acid (L) solutions in reducing aerobic psychrotrophic bacteria plate counts (PPCs) and lactic acid bacteria counts (LACs) on vacuum-packaged beef was investigated at 0, 14, 28 and 56 days of storage. Instrumental and visual color changes were evaluated up to 28 days. Steaks treated with 1.5% L, plus 1.5% G or 3.0% G, solutions showed 2.0 and 2.5 log reductions (P<0.05) in PPCs compared to nontreated samples, respectively, at days 28 and 56. At 1.5%, G or L intervention for 0 and 14 days PPCs did not differ (P>0.05). However, PPCs were lower (P<O.05) for samples treated with 1.5% L than with 1.5% G at 28 and 56 days of storage. The effect of G plus L in reducing (P<0.05) LACs was evident at all storage periods. Inoculation with Lactobacillus fermentum (104 colony forming units [CFU]/ml) resulted in higher (P<0.05) PPCs and LACs at 28 and 56 days compared to noninoculated counterparts. Increasing G from 1.5 to 3.0% decreased (P<0.05) redness and increased (P<0.05) yellowness at day 0. Samples treated with 1.5% L solution had numerically the lowest a* values at days 0 and 14. This detrimental effect was reduced (P<0.05) when 1.5% G was added in combination with L, because redness increased (P<0.05) at day 14. At 0 day, 1.5% L steaks showed the fastest (P<0.05) rate of color deterioration. At 14 days, the presence of L alone or in combination with 1.5 or 3% G resulted in steaks with slightly faster (P<0.05) color deterioration compared to steaks treated with G or not treated. At day 28, 3.0% G samples revealed the fastest (P<0.05) color deterioration. This detrimental effect on color was reduced (P<O.05) when G plus L was applied at 1.5%.