Purpose: The objective of this project was to quantify the contribution of human error to temperature probe placement in meat patties, which subsequently affects error in endpoint temperature and lethality determination.
Methods: Two different groups of human subjects were tested. The first group (n = 12) consisted of laboratory personnel with experience working with meat patties and temperature probes. The second group (n = 20) consisted of individuals solicited from the general university population. Each subject was presented with three beef patties (thickness ~ 1.2 cm; diam ~ 12 cm) and three rigid temperature probes connected to wire leads. The subjects were instructed to insert one probe through the side of each patty so that the tip was in the geometric center. Each tray was then frozen to fix the probe positions. The samples (n = 96) were subsequently scanned via computed tomography (CT). The CT images (resolution 0.625 x 1.00 mm) were processed using Matlab to identify the centroid of each patty and the location of the probe tip relative to the centroid.
Results: For the lab and public groups, respectively, the mean (± standard deviation) vertical errors in position (i.e., bias), were -1.5 ± 2.9 and -2.8 ± 3.3 mm; the mean absolute vertical errors were 2.7 ± 1.8 and 3.1 ± 2.6 mm; and the mean total distances from the centroid were 6.9 ± 4.0 and 10.5 ± 6.7 mm.
Significance: We have previously reported that temperature probe errors of 3 mm in a convection cooked patty can yield lethality errors of ~5 log, or correspond to increased required endpoint temperature or cooking time of 9 °C or 40 s. Overall, human error in temperature probe position can contribute significantly to the inherent uncertainty in thermal process validations, and should be accounted for in such analyses.