Residential Refrigerator Performance Based on Microbial Indicators of Ground Beef Preservation Assessed Using Predictive
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ORIGINAL RESEARCH
Residential Refrigerator Performance Based on Microbial Indicators of Ground Beef Preservation Assessed Using Predictive Microbiology Tools Reynaldo de la Cruz Quiroz 1 & Veronica Rodriguez-Martinez 1 & Gonzalo Velazquez 2 & Gabriel M. Perez 3 & Fabian Fagotti 3 & Jorge Welti-Chanes 1 & J. Antonio Torres 1 Received: 27 July 2020 / Accepted: 29 October 2020 / Published online: 12 November 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The aim of this study was to develop a refrigerator performance assessment procedure based on the temperature (2 × 106 values) of ground beef stored in its bottom drawer set to Fresh Meat (0 °C). Effects analyzed were ambient temperature (LT, 21.1 °C/HT, 32.2 °C), food load (LL, 22.5 kg/HL, 39.0 kg), door openings, and refrigerator compressor mode (SS, single speed/VS, variable speed). Published predictive microbiology models for exponential growth and ground beef temperature (48-h tests) were used to define absolute (API) and relative preservation indicators (RPI). For VS mode, API (log CFU/g) ranged from 1.7 (LT/LL) to 3.1 (HT/HL) for Listeria monocytogenes and 1.6 to 2.5 for Pseudomonas putida. Ground beef temperature reductions with minimum freezing risk yielded significantly lower API values indicating the need for refrigerator settings below 5 °C. Probabilistic analysis considering the model and temperature measurement variability confirmed this need. At 2 °C as recommended for ground beef storage, API2°C would be 1.1 (L. monocytogenes) and 1.4 logCFU/g (P. putida). RPI defined as the ratio of experimental API over API2°C yielded values > 1 confirming that a refrigerator control logic must consider preservation in addition to energy use compliance. In this study, SS outperformed energy-efficient VS compressors; however, compressor optimization considering energy use and food preservation would favor the latter. In conclusion, API and RPI values were effective tools to assess the microbial food preservation performance of a refrigerator and its use could be extended to analyze any segment of the refrigerated food distribution chain. Transforming time-temperature data into microbial performance indicators is practical and cost-effective. Keywords Refrigerator preservation performance . Absolute preservation indicator . Relative preservation indicator . Microbial safety . Microbial spoilage . Refrigerated foods
Nomenclature API (log CFU/g)
Absolute preservation indicator defined as the cumulative exponential increase in counts during the preservation
Reynaldo de la Cruz Quiroz and Veronica Rodriguez-Martinez contributed equally to this work.
APILm (log CFU/g) APIPp (log CFU/g) b CFU/g
1
Tecnologico de Monterrey, Escuela de Ingeniería y Ciencias, 64849 Monterrey, NL, Mexico
HL HT LL LT RPILm
2
Instituto Politécnico Nacional, CICATA-IPN Unidad Queretaro, 76090 Santiago de Queretaro, QRO, Mexico
RPIPp
* J. Antonio Torres [email protected]
3
Embraco Mexico S de RL de CV, 66603 Apodaca, NL, Mexico
performance
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