Microbial preservation performance evaluation in residential refrigerators: A multiple product, refrigerator placement and temperature setting case study

Abstract

The microbial preservation performance of a residential refrigerator was evaluated using a Refrigeration Preservation Indicator (RPI) based on the square root model, a frequently used secondary predictive microbiology model, and time-temperature data collected for whole milk, panela cheese and chicken breast meat. RPI values <1, ∼1, and > 1 indicating excellent, acceptable, and poor preservation performance, respectively, were used to assess effects of product placement (door/body shelves, and drawer independently controlled at 0 °C), setting (2/4/5 °C), ambient temperature (21.1 °C [LT] and 32.2 °C[HT]), and load (24.9 kg regular [RL] and 39 kg high load [HL]). Lowering the temperature setting significantly improved RPI values for all product/placement locations. While poor performance was observed at 5 °C with RPI values reaching 3.74 for milk and 1.38 for cheese, for the 2 °C setting, the corresponding values were 1.56 and 1.00. Chicken breast stored in the closed drawer with independent temperature control consistently achieved excellent performance with values ranging 0.42–1.16 across treatments. Under HL conditions, the temperature increase caused by door openings was buffered, but temperature recovery exceeded 30 h. Lowering the temperature setting to 2 °C reduced it to 9.4 h. Product exposure to ambient temperature emulating consumer product use increased RPI variability, as illustrated by one-sided 95% confidence intervals. Finally, refrigerator design improvements were identified to mitigate the lowering of food preservation performance of residential refrigerators caused by door openings and high ambient temperatures. Finally, RPI values can be used to assess the preservation performance of any cold chain component.