Purpose: The purpose of this study is to determine the accuracy of infrared technology in performing temperature audits of packaged cut leafy greens in retail cold-chain display.
Methods: Thirty ‘point-of-sale’ commercially-bagged baby spinach products were purchased at retail. Each bag was manually opened and individual temperature dataloggers were placed in the middle of the product. The bags were resealed to original specifications and placed in the outermost shelf locations in a new, commercial, 12-foot refrigerated open-display case operating at the industry-recommended thermostatically-controlled temperature-defrost schedule. Temperature measurements from each bag were also collected manually using a hand-held infrared thermometer at random times through the daily operation (including defrost periods) of the retail display case. Thermograph profiles obtained from each bag, shelf, and the ambient conditions were also determined.
Results: Bland-Altman and regression analysis of the non-contact infrared and the internal bag temperature datalogger data showed a significant bias between the measurements; the infrared technology overestimated the leafy green product temperature by approximately 3°F. Furthermore, when temperatures were obtained at the end of the display case defrost cycle (maximum case thermostat temperatures), the mean difference between the two measurement methods dramatically increased and the internal produce temperatures were overestimated by greater than 9°F using infrared technology.
Significance: Temperature monitoring and auditing must reflect the actual product temperatures. Infrared technology is simple, easy and widely used, but does not accurately reflect internal product temperature of bagged baby spinach.