ABSTRACT
Samples of fresh pork skin were inoculated with known numbers of a nalidixic acid-resistant strain of Campylobacter jejuni and sampled by two methods, swabbing and scraping, 10 min after inoculation to compare sampling methods. The effect of frozen storage of samples on detection was also examined. C. jejuni was readily recovered with swab samples while recovery of the organism was greatly reduced by the scrape method. Frozen storage of samples decreased the numbers of viable cells as compared to the fresh samples.
ABSTRACT
Ground pork longissimus or beef semimembranosus muscle was heated in stoppered glass tubes in a controlled temperature bath at 60, 65, 67.5, 70, or 75°C and held for 0, 7.5, 15 or 30 min after the sample reached the desired internal temperature, removed, and cooled (0-2°C) immediately. Heated samples were homogenized with deionized water at a ratio of 1:3.3 (w/v) muscle to water. The amount of water-extractable proteins was determined by the biuret method. Eight ml of clear extract from each treatment was reheated for 15 min at 70°C, removed, and cooled (0-2°C) immediately. Coagulum was removed by filtration (0.45 µm), and a biuret measurement made on the clear extract. These two values were used to calculate a water-extractable biuret-positive ratio (EBPR) value for a specific time/temperature treatment. The base value of 70°C was selected for the ratio because it represents a temperature slightly above that necessary for thermal inactivation of certain animal viruses required by USDA-APHIS/FSIS for certain imported canned meat products. Heat denaturation/coagulation of water-extractable, biuret-positive bovine and porcine compounds with subsequent solubility loss was a time/temperature-dependent process through 70°C. EBPR values for bovine and porcine muscles heated up to 60, 65, 67.5, 70, or 75°C with no holding time were 2.11, 1.23, 1.08, 1.07, 1.02 and 2.88, 1.65, 1.13, 1.04, and 1.02, respectively. Using 70°C as the critical denaturation/coagulation temperature, EBPR values for beef and pork were 1.07 ± .024 and 1.04 ± .066, respectively. Upper 95% confidence limits were 1.30 for beef and 1.12 for pork.
ABSTRACT
One hundred and twelve freshly slaughtered pork carcasses from three packing plants were sampled before and after chilling for the presence of Campylobacter jejuni / coli by the use of two isolation methods (Preston enrichment and Skirrow direct plating). Preston enrichment media gave the highest isolation rate, 12.5%, on freshly slaughtered carcasses. No isolations were obtained from chilled carcasses. More isolates were obtained from the ham skin area compared with the jowl area. All isolates were confirmed as Campylobacter coli .
ABSTRACT
Pork skin inoculated with a nalidixic acid-resistant strain of Campylobacter jejuni was subjected to three treatments to determine the effect of storage temperature, oxygen concentration, and drying on survival of the organism. Survival rate was determined for each treatment by enumeration over a 48-h period on Brucella agar containing nalidixic acid. Of the treatments studied, chilling with forced ventilation and storage at 20°C caused significant reductions in numbers of survivors. The results of this study confirm reports by other investigators that conventional forced ventilation chilling of pork carcasses has the beneficial effect of reducing skin surface Campylobacter contaminants.
