Evaluation of the Reveal and SafePath rapid Escherichia coli O157 detection tests for use on bovine feces and carcasses.

The Reveal (Neogen Corp., Lansing, Mich.) and SafePath (SafePath Laboratories LLC, St. Paul, Minn.) tests were evaluated for their performance as beef fecal and beef carcass Escherichia coli O157:H7 monitoring tests. Agreement between these tests and a reference test system was determined using naturally contaminated bovine feces and beef carcasses. The reference system utilized immunomagnetic separation with plating onto cefixime, tellurite, sorbitol MacConkey agar, followed by colony testing using a serum agglutination test for the O157 antigen. Relative to this reference method, the Reveal test showed a sensitivity of 46% and a specificity of 82% on bovine feces and a specificity of 99% on carcass samples. The SafePath test, demonstrated a significantly higher sensitivity at 79% and a similar specificity of 79%. On carcass samples the SafePath test performed similarly to the Reveal test, demonstrating a specificity of 100% relative to the reference system. There was an insufficient number of E. coli O157-positive carcass samples to estimate precisely the sensitivity of these two methods. Both methods show promise as rapid carcass monitoring tests, but further field testing to estimate sensitivity is needed to complete their evaluation. The proportion of positive fecal samples for E. coli O157:H7 by the reference method ranged from 10.2% to 36% in 10 lots of cattle with an overall mean of 17.3% (39/225). Quarter carcass sponging of 125 carcasses revealed 1.6% positive for the pathogen (2/125).

The role of microbiological testing in systems for assuring the safety of beef.

The use of microbiological testing in systems for assuring the safety of beef was considered at a meeting arranged by the International Livestock Educational Foundation as part of the International Livestock Congress, TX, USA, during February, 2000. The 11 invited participants from industry and government research organizations concurred in concluding that microbiological testing is necessary for the implementation and maintenance of effective Hazard Analysis Critical Control Point (HACCP) systems, which are the only means of assuring the microbiological safety of beef; that microbiological testing for HACCP purposes must involve the enumeration of indicator organisms rather than the detection of pathogens; that the efficacy of process control should be assessed against performance criteria and food safety objectives that refer to the numbers of indicator organisms in product; that sampling procedures should allow indicator organisms to be enumerated at very low numbers; and that food safety objectives and microbiological criteria are better related to variables, rather than attributes sampling plans.

Extending the retail storage time of pork sausage using modified atmospheres and freezing.

Two experiments were conducted to evaluate the effect of different gas mixtures on the keeping quality of fresh pork sausages. The modified atmospheres consisted of combinations of oxygen, carbon dioxide, and nitrogen. In the first experiment, 15 gas combinations of these two gases plus oxygen were evaluated. The samples were stored at 5°C for up to 16 days. The variables used to evaluate the quality of the sausages included acceptability, hardness, cohesiveness, hue, pH, total plate counts, coliforms and water holding capacity. The results showed a negative effect of oxygen upon most of the variables. Based on these results, the second experiment was designed to evaluate the effect of frozen storage upon the quality of the samples against non-frozen storage (5°C). Six gas combinations of carbon dioxide and nitrogen were used. The results favoured frozen storage and high carbon dioxide levels (60% to 80%).

Effect of hot-boned pork on the keeping quality of fresh pork sausage.

The first experiment evaluated the effect of solid carbon dioxide (dry ice) addition to hot-boned meat, in different proportions, upon the keeping quality of fresh pork sausage patties. Dry ice had some negative effects at levels of 20% to 40%, such as hardening and colour fading of samples, although it increased water-holding capacity of the sausage. In the second experiment three proportions of hot-boned meat and chilled meat were evaluated as a means to extend the retail storage time of fresh pork sausage links. Hot-boned pork was treated by three methods: freezing the meat before grinding, salting and freezing, and salting plus dry ice addition. The results favoured the use of 50% hot-boned meat and 50% chilled meat, for which the lowest hardness and oxidation values were obtained. Microbial counts and hue values showed no significant variation among the three treatments. Salting and freezing hot-boned meat before grinding was the method which produced the best overall quality.

Meat emulsion functionality related to fat-protein ratio and selected dairy and cereal products.

The influence of fat-protein ratio, moisture content, buttermilk powder, modified wheat flour, corn starch and modified waxy maize flour in processed meat emulsions upon their sensory attributes, textural profile parameters, and selected functional properties were investigated. These properties were optimized using regression models, canonical analysis, response surface methodology, and a multidimensional optimization algorithm.

An Evaluation of Antibotulinal Activity in Nitrite-Free Curing Systems Containing Dinitrosyl Ferrohemochrome.

The ability of the pigment dinitrosyl ferrohemochrome to mimic the cured meat color function attributed to nitrite, was evaluated in a number of nitrite-free, model meat systems. In addition, compounds with reported antibotulinal properties were compared to the antibotulinal effect of nitrite. Fifteen treatments were evaluated and compared to 50 and 150 ppm nitrite. Two processing conditions (short and extended heating) were also compared for their ability to enhance pigment color and eliminate the natural meat microbial population. Meat slurries varying in cure composition were inoculated with a composite of six different strains of Clostridium botulinum , types A and B. After processing, the packages were incubated at 10 and 27°C, and were analyzed for toxin. The treatment containing 3000 ppm sodium hypophosphite most closely resembled the 150 ppm nitrite control in its ability to prevent spore outgrowth and toxin production. The treatment containing 1250 ppm monomethyl fumerate also scored better than the other treatments including ethylene diamine tetraacetic acid (EDTA), potassium sorbate and tertiary butyl hydroquinome (TBHQ), but was slightly less inhibitory than sodium hypophosphite. The longer heat treatment eliminated all the natural meat flora (lactic acid bacteria) and enhanced the color production of the pigment.

Nisin Sensitivity of Lactic Acid Bacteria Isolated from Cured and Fermented Meat Products.

Thirty strains of lactic acid bacteria from different meat sources (bologna, summer sausage, thurlinger sausage, chicken loaf and bacon) were tested for nisin sensitivity. The maximum concentration of nisin permitting growth for 20 strains was 50 IU/ml. Lactobacilli classified as atypical were sensitive to <5 IU nisin/ml. These strains could not be induced to increase resistance by five transfers to media with increased nisin concentrations. The ten strains with the higher resistance to nisin were checked for nisinase activity. One strain, Lactobacillus brevis , showed weak nisinase activity and the rest were negative.

Shelf-Life Studies of Vacuum-Packaged Bacon Treated with Nisin.

The effect of various concentrations of nisin (250, 500 or 750 IU/g) combined with 50 ppm sodium nitrite on the shelf-life of vacuum-packaged bacon was evaluated. Control packages of bacon containing 50 and 150 ppm nitrite were included. Total numbers of lactic acid bacteria (LAB) (as measured on MRS medium) was used as a criterion for shelf-life. Treated bacon samples were stored at 30 and 5°C for 4 d or 6 wk, respectively. Bacon stored at 30°C showed a 1-d extension of shelf-life at nisin levels of 500 and 750 IU/g. Lowest counts at 6 wk were in bacon treated with 750 IU nisin and stored at 5°C. The LAB count was 1.5-log10 CFU/g lower than the controls. A 1-wk extension of storage life was predicted for nisin-treated (750 IU) bacon.

The efficacy of chlorine dioxide in controlling Salmonella contamination and its effect on product quality of chicken broiler carcasses.

A large spin-type chiller in an Ontario poultry processing plant was adapted so that the chill water could be treated with various levels of chlorine dioxide ( ClO2 ), increasing the concentration of ClO2 from 0 to 1.39 mg/liter resulting in reducing the bacteria count to the point where salmonellae could not be isolated from the chill water or the chilled broiler carcasses. In addition, coliform, psychrotroph , and aerobic plate counts were all greatly reduced (less than 1 log cycle) in chill water but were only slightly reduced (less than .5 log cycle) in macerated chicken broiler breast skin. Shelf-life was lengthened for broiler carcasses treated with 1.33 and 1.39 mg/liter ClO2 as compared to control carcasses. Sensory panelists reported no off flavors for any ClO2 concentration but rated broiler skin as being slightly lighter in color compared to control carcasses at all concentrations of ClO2 treatment.

Mojonnier method as reference for infrared determination of fat in meat products.

The Mojonnier method was compared with the conventional Soxhlet method for the determination of fat in 7 different meat products to assess its use as a standard reference method for calibration of commercial quantitative infrared transmission analyzers (e.g., Multispec M, Milkoscan 300 or 104). Results for the meat samples obtained by the Mojonnier method did not differ significantly from those obtained by the Soxhlet method. In addition, the Mojonnier method was less time-consuming and more precise than the Soxhlet; therefore, it can be used as a standard reference procedure for the calibration and assessment of infrared milk analyzers in their potential application to the rapid determination of fat in meat and meat products.

Organoleptic, Chemical and Bacterial Characteristics of Meat and Offals from Beef Cattle Fed Wet Poultry Excreta.

Three groups of growing-finishing beef cattle were fed soybean meal, urea or acetic-propionic acid-treated wet-cage layer excreta as a protein supplement for 125 days. Rib-roasts from the cattle were evaluated for cooking loss, juiciness, flavor, tenderness and overall acceptability. Rib cuts were analyzed for moisture, fat and protein, and samples of the liver, heart, kidney, and longissimus muscle were analyzed for cadmium, lead, copper, iron, calcium and phosphorus. In addition, gall bladders and mesenteric lymph nodes obtained from the cattle at slaughter as well as layer excreta samples were cultured for salmonellae. No significant differences were found in any of the factors studied. Salmonellae were isolated from the cage layer excreta, but not from cattle tissues. Apparently, feeding organic acid-treated wet cage layer excreta to cattle would not affect the nutritive value, organoleptic quality or wholesomeness of beef.