Trichinella spiralis: effect of high temperature on infectivity in pork

Twenty gram samples of homogenized Boston shoulder from swine experimentally infected with Trichinella spiralis were sealed in plastic pouches, pressed to a uniform thickness of 2 mm, and subjected to water bath temperatures of 49, 52, 55, 60, and 63 +/- 0.5 C for intervals of 2 min to 6 hr, especially within the interval of 0 to 15 min. These times included a period of about 1 min at the start and a period of about 1 min at the end for temperature equilibration. Treated samples were rapidly chilled to 25 C and then digested in a 1% pepsin-HCl solution at 37 C for 18 hr to recover T. spiralis larvae. The recovered larvae were suspended in 2 ml saline; 1 ml of this suspension was introduced into the stomach of each of two rats. The linear equation, log (time) = 17.3 -0.302 (temperature), was calculated from the time required at each temperature for the inactivation of T. spiralis larvae. The correlation coefficient for that relationship was r = -0.994. Larvae heated in the meat to 55 C for 4 min retained their infectivity, but were rendered noninfective after 6 min at 55 C. At 60 C, larvae were not infective after only 2 min (zero dwell time); whereas at 52 C, 47 min were required to render the larvae noninfective. Larvae in meat heated to 49 C were infective after 5 hr but not after 6 hr. These data demonstrate that the destruction of infectivity of T. spiralis is time-temperature related.