The combination of vacuum and dry saturated steam in an autoclave is extremely efficient to kill bacteria at a precisely controlled temperature. Due to process automation, steam pasteurization also does not depend upon operator performance to thoroughly treat tissue surfaces and prevent cross- or recontamination by adhering to strict operational sanitation procedures. Several researchers have also investigated steam-vacuuming in combination with other treatments for reducing bacterial contamination on carcass surfaces (Dorsa et al., 1996, 1997a; Phebus et al., 1997; Castillo et al., 1999a). Steam treatment for up to 10 sec on chicken portions inoculated with a nalidixic acid- resistant strain of Escherichia coli serotype 080 resulted in a maximum reduction of 1.90 log cfu per cm2. As already indicated, US slaughter facilities are utilizing knife-trimming or steam-vacuuming of < 2.5 cm diameter areas to comply with the zero-tolerance policy for visible physical contamination (Sofos and Smith, 1998; Sofos et al., 1999a; Gill, 2004; Koutsoumanis et al., 2005). This is not surprising since knife-trimming and water washing are regarded mostly as cleaning treatments and not processes that decontaminate and enhance the safety of the product. Fig. In experimental studies, whole chicken carcasses, inoculated with Campylobacter jejuni and Escherichia coli K12, were treated with steam at atmospheric pressure for up to 20 s in a pilot-scale cabinet (and with hot water in a pilot immersion system for 20–30 s at 75 and 80 °C). Constraints include reluctant consumer acceptance of radiation-treated food, increased price of production, and the irradiation's negative effect on odor and flavor. Generic E. coli populations were below the detection limit at 32% of the locations before treatment and below the detection limit on a majority of the carcasses (85%) after treatment. Studies on this com- mercially-available system for treating red-meat carcasses have been conducted and published by Kansas State University (Nutsch et al., 1997; Phebus et al., 1997). Blanching and roasting, in particular, result in significant changes in texture, flavor, and color attributes. D.R. (2002) describe trials on steam pasteurisation of gutted and defined whole salmon using bespoke treatment equipment. Numbers of campylobacters were reduced, but not eliminated. The combination treatments were also found to effectively reduce contamination dispersed outside the inoculated area as a result of steam-vacuuming. Atmospheric steam treatments have been shown to have potential for treating fish, specifically catfish (Balá et al., 1999) and salmon (Bremer et al., 2002). Due to process automation, steam pasteurization also does not depend upon operator performance to thoroughly treat tissue surfaces and prevent cross- or recontamination by adhering to strict operational sanitation procedures. Exposure to an 8 second commercial steam pasteurization process reduced pre-treatment aerobic plate counts associated with fed and non-fed carcass surfaces from 2.1 and 2.2 log CFU/cm2, respectively, to 1.0 and 0.8 log CFU/cm2. Application of steam at atmospheric pressure (100 °C for 10 sec) on naturally-contaminated chicken breast portions resulted in a 1.65 log cfu per cm2 reduction in TVC. Without the cold core, which in effect is a heat sii.k, to deflect the spiralling increase in temperature, thermal momentum continues for an hour or two beyond the time steam injection is shut off. Phebus et al. However, the 20 s treatments caused the skin to shrink and change colour. Thus, it follows that pathogen reduction efforts applied throughout the animal production and processing chain should reduce the risk of E. coli O157:H7 occurrence in the final beef products. (2003) did not examine hides, but also did not see an increase in E. coli O157 fecal shedding by cattle as a result of transportation and lairage. Similar to other non-discriminating decontamination strategies, antimicrobial efficacy of a steam pasteurization process is not dependent upon visually identifying gross contamination. Thus, there are four parameters of steam sterilization: steam, pressure, temperature, and time. Thus, it follows that pathogen reduction efforts applied throughout the animal production and processing chain should reduce the risk of E. coli O157:H7 occurrence in the final beef products. Research has demonstrated that steam pasteurization in a commercial plant results in a 1–2 log reduction in aerobic plate counts. Steam at 100°C has a much higher heat capacity than water at the same temperature, so if steam condenses on a surface, the temperature of that surface rises more rapidly than if it were water that was deposited on the surface. The researchers also reported significant treatment-dependent reductions in Enterobacteriaceae counts approximating those observed for total coliforms (Nutsch et al., 1998). Most studies on the utilisation of atmospheric steam have aimed to develop processes that produce a substantial reduction in microbial numbers, but do not result in substantial cooking of the product. For atmospheric steam (96–98 °C), a 3 min treatment was required to reduce natural contamination of retail carcasses from 104 to < 6 CFU cm−2. The full commercial system (SPS 400 Steam Pasteurisation System) consists of a three-stage cabinet. Gill and Bryant (1997) randomly selected and sampled surfaces of 50 carcasses and determined microbiological counts both before and following exposure to a commercial steam pasteurization process. In this work a 90 °C for 10 s treatment was favoured, producing reductions in inoculated Enterobacteriaceae of up to 3 log CFU cm−2 on treated beef carcasses (Eveleigh, 2000). Irradiation of beef in the postharvest stage is a process that could be used to inactivate pathogens. Carcasses then are sprayed with cold water. The appearance of the treated carcasses was assessed visually at intervals until the end of shelf-life, and checks made for pseudomonas, Enterobacteriaceae and campylobacters on breast skin. Tissue surfaces associated with each region were sponge-swabbed (300 cm2) both before and after treatment application for 6.5 seconds. In an additional study, when fecally contaminated carcass surfaces were treated by steam-vacuuming followed by hot water (82 °C at carcass surface, 5 seconds), 2% lactic acid (55 °C, 11 seconds), or hot water and lactic acid sprays, reductions in aerobic plate counts for the combination treatments ranged from 3.5–4.4 log10 CFU/cm2, while the reduction attained by steam-vacuuming alone was 2.7 log10 CFU/cm2 (Castillo et al., 1999a). A modified version of this system has been evaluated in a UK red-meat abattoir, and Whyte et al. 8.2. However, after an in-plant study, Dorsa (1997) concluded that steam-vacuuming could out-perform knife-trimming in reducing bacterial populations from < 2.5 cm diameter contaminated areas. 1)If the fat content of the milk product is ten percent (10%) or more, or if it contains added sweeteners, or if it is concentrated (condensed), the specified temperature shall be increased by 3ºC (5ºF). The effect of such treatment on sensory characteristics was not discussed; however, it was noted that exposed muscle surfaces were discoloured and that the skin developed a white film after heating. Many of these same studies also have shown that the effectiveness of antimicrobial carcass interventions is improved by reducing the pathogen load at previous steps in the process (Arthur et al., 2004; Brichta-Harhay et al., 2008; Woerner et al., 2006a). Investigations have been carried out using a mixture of C. jejuni and E. coli K12 (a surrogate for Salmonella), inoculated onto the breast skin of carcasses. The handheld device includes a vacuum wand with a hot water spray nozzle, which delivers water at approximately 82°C to 88°C (180°F–190°F) to the carcass surface, as well as the vacuum unit.

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