COMPARING INFRARED AND PROBE THERMOMETERS TO MEASURE THE HOT HOLDING TEMPERATURE OF FOOD IN A RETAIL SETTING Rohit C., Moos M., Meldrum R., Young I. School Of Occupational and Public Health, Ryerson University • The fundamental technical difference between probe and infrared thermometer is that infrared thermometer provide the surface temperature of the food item whereas the probe thermometer offers the internal temperature . • Food safety regulations in Ontario for the food service and retail sector requires that potentially hazardous food that is kept hot must be held at an internal temperature of ≥ 60 ° C . This limits the use of an infrared thermometer for food safety compliance . • This research examines the relationship between the internal temperature of the hot holding food measured via probe thermometer and the surface temperature measured via infrared thermometer in a retail setting . BACKGROUND PURPOSE • Seven different stores (Store A to Store G) from one major retail chain in Greater Toronto Area were visited six times each during February and March 2018 . • Seven different hot held food items (whole chicken, chicken strips, chicken pieces, breaded chicken wings, honey garlic chicken wings, potato wedges, ribs) were sampled twice for internal temperature via probe thermometer and twice for the corresponding surface temperature via infrared thermometer during each visit . • Both types of measurements were taken using a ParTech TMD ( ParTech , Inc . Toronto) . • The sampling time and store cooking time record were used to calculate a variable ‘elapsed time’ – amount of time a food product setting in the hot hold unit . Other variables included in the research were total quantity of food items in the hot holding unit (number of food boxes), temperature of the hot - holding unit, and outside weather temperature (via the Weather Network mobile app) . • The data were analyzed using Microsoft Excel and SPSS software . Figure 1 Figure 2 Figure 1 : This graph shows probe measurement values for given infrared values at each sample point . At the lower infrared temperatures (< 60 ° C), the internal temperature is usually higher, and at the higher temperature level, the effect is inversed . This can be explained by the surface of the food cooling down faster in comparison to the center of the food . Figure 2 : This graph shows the strong positive correlation between the probe temperature and the infrared temperature . MATERIALS AND METHODS • The Pearson Correlation test shows a significant positive correlation ( r = 0 . 706 , n = 212 ) between the probe and infrared measurements . • The correlation between the probe and infrared measurements differed among the food items, with breaded chicken wings having the highest correlation ( r = 0 . 867 , n = 35 ) and potato wedges having the lowest correlation ( r = 0 . 592 , n = 39 ) • The correlation between the two thermometer types also differed by store . • The elapsed time variable (preparation time – sampling time) had a negative correlation with both the probe ( r = - 0 . 261 , n = 182 ) and infrared ( r = - 379 , n = 182 ) measurements . RESULTS DISCUSSION • The research showed a strong positive correlation between the probe and infrared thermometers and that indicate a possibility of developing a predictive model to estimate the internal temperature of food via infrared thermometers . • Such a model will make the use of infrared thermometers more reliable for food safety compliance by the food service industry . • The elapsed time had a negative correlation with both the probe and infrared temperatures and the result suggests that longer the food stays in the hot holding unit the more likely that it will have lower temperature . • The research had some limitations, including use of only one type of thermometer, one retail chain, and limited types of food products . DESCRIPTIVE ANALYSIS OF STUDY VARIABLES FOR ALL FOOD ITEMS Mean SD N Hot Holding Unit Temp(°C) 74.64 10.69 33 Hot Holding Unit Food Quantity 21.53 9.75 43 Time Elapsed(h:mm) 1:59 1:32 182 Probe Temp(°C) 66.05 6.38 212 Infrared Temp(°C) 64.95 9.19 212 Difference b/w Probe & Infrared(°C) 5.38 1.10 212 Outside Temp(°C) 1.76 3.30 294 PEARSON CORRELATION BETWEEN EXPLANATORY VARIABLES AND TEMPERATURE MEASUREMENTS Variable Probe Infrared r p N r p N Hot Holding Unit Temp -0.109 0.171 159 -0.293 0.01 159 Hot Holding Unit Food Quantity 0.021 0.766 212 -0.131 0.58 212 Time Elapsed -0.261 0.01 182 -0.379 0.01 182 Outside Temp 0.053 0.439 212 0.059 0.396 212 CORRELATION BETWEEN THE PROBE AND INFRARED TEMERATURES, STRATIFIED BY FOOD TYPE AND STORE LOCATION Variable r p N Food Type Whole Chicken 0.741 0.01 42 Chicken Stripes 0.837 0.01 32 Chicken Pieces 0.756 0.01 36 Breaded Chicken Wings 0.867 0.01 35 Honey Garlic Chicken Wings 0.677 0.01 27 Potato Wedges 0.592 0.01 39 Ribs - - 1 Store Type Store A 0.569 0.01 35 Store B 0.744 0.01 26 Store C 0.866 0.01 35 Store D 0.531 0.01 28 Store E 0.603 0.01 26 Store F 0.907 0.01 29 Store G 0.719 0.01 31 All data 0.706 0.01 212