Inactivation of Mycobacterium avium subsp. paratuberculosis during Cooking of Hamburger Patties

Abstract

The role of Mycobacterium avium subsp. paratuberculosis (MAP) in Crohn's disease in humans has been debated for many years. Milk and milk products have been suggested as possible vectors for transmission since the beginning of this debate, whereas recent publications show that slaughtered cattle and their carcasses, meat, and organs can also serve as reservoirs for MAP transmission. The objective of this study was to generate heat-inactivation data for MAP during the cooking of hamburger patties. Hamburger patties of lean ground beef weighing 70 and 50 g were cooked for 6, 5, 4, 3, and 2 min, which were sterilized by irradiation and spiked with three different MAP strains at levels between 10² and 10⁶ CFU/ml. Single-sided cooking with one flip was applied, and the temperatures within the patties were recorded by seven thermocouples. Counting of the surviving bacteria was performed by direct plating onto Herrold's egg yolk medium and a three-vial most-probable-number method by using modified Dubos medium. There was considerable variability in temperature throughout the patties during frying. In addition, the log reduction in MAP numbers showed strong variations. In patties weighing 70 g, considerable bacterial reduction of 4 log or larger could only be achieved after 6 min of cooking. For all other cooking times, the bacterial reduction was less than 2 log. Patties weighing 50 g showed a 5-log or larger reduction after cooking times of 5 and 6 min. To determine the inactivation kinetics, a log-linear regression model was used, showing a constant decrease of MAP numbers over cooking time.

Detection of Mycobacteria by Culture and DNA-Based Methods in Animal-Derived Food Products Purchased at Spanish Supermarkets

“…Since these infections are more common in older animals, we find more likely that this sausage contained meat from culled laying hens instead of young broilers specifically bred for meat and deduce that improved control measures are desirable. Raw meats are generally intended for being consumed cooked, but eating undercooked meats is quite common and mycobacterial inactivation during cooking is time and temperature dependent (Hammer et al, 2013). In addition, cooked products can become cross-contaminated through direct or indirect contact with raw meat as a consequence of improper food handling.…”

Survey on the presence of Mycobacterium avium subsp. paratuberculosis in ground beef from an industrial meat plant

“…A study showed that the cooking of meat at a temperature of 75 8C ensures the inactivation of MAP, whereas lower temperatures (at 61 and 71 8C, respectively) may allow its survival (Mutharia et al, 2010). Hammer et al (2013) reported that the effectiveness of cooking in reducing the concentration of viable MAP depends on the size of the hamburger and on the cooking time. A decay of about 4 log of MAP was observed by cooking a hamburger of 70 g for 6 min, while a decay of about 5 log of MAP was observed in hamburgers of 50 g cooked for 5 min.…”

“…Furthermore, this last paper (Hammer et al, 2013) stressed how the heating of meat has lower efficiency in reducing the concentration of viable MAP cells, compared to its application to the meat juice. In fact, a study conducted using lamb meat juice artificially contaminated with two strains of MAP (S-type and C-type), highlighted that a temperature of 75 8C for 5 s leads to a total inactivation of MAP at concentrations less than or equal to 10 5 MAP/100 mL .…”

Short communication: Effect of homogenization on heat inactivation of Mycobacterium avium subspecies paratuberculosis in milk

“…The sample temperature at collection was <12°C and further cooling was not applied. Directly after collection (maximum of 1-h delay), samples were processed as described in Hammer et al (2013).…”