How does a refrigerator keep food cold, and what do the temperature zones mean?

Numbers match the citations in the article. A working link isn't proof that a page supports a claim; check the quoted passage and date.

1. 1

   Refrigerator (Wikipedia)

   WikipediaPublished Oct 15, 2026Checked Oct 17, 2026

   “A refrigerator, commonly shortened to fridge, is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic, or chemical) that transfers heat from its inside to its external environment so that its inside is cooled to a temperature below the ambient temperature of the room. Refrigeration is an essential food storage technique around the world. The low temperature reduces the reproduction rate of bacteria, so the refrigerator lowers the rate of spoilage. A refrigerator maintains a temperature a few degrees above the freezing point of water. The optimal temperature range for perishable food storage is 3 to 5 °C (37 to 41 °F). A freezer is a specialized refrigerator, or portion of a refrigerator, that maintains its contents' temperature below the freezing point of water. The refrigerator replaced the icebox, which had been a common household appliance for almost a century and a half. The United States Food and Drug Administration recommends that the refrigerator be kept at or below 4 °C (40 °F) and that the freezer be regulated at −18 °C (0 °F). The first cooling systems for food involved ice.”

2. 2

   Microbial Survival, Sublethal Injury, and Recovery in Frozen Food Systems: Implications for Safety, Quality Deterioration, and Cold-Chain Control.

   Comprehensive reviews in food science and food safety (Chen et al.)Published Sep 1, 2026Checked Oct 17, 2026

   “Rather than treating sublethal injury, viable but non-culturable (VBNC) physiology, spoilage, detection methods, and freezing-thawing processes separately, we integrate them into a recovery-centered framework for frozen food systems. Particular attention is given to food-matrix effects, including water redistribution, nutrient release, fat and protein composition, surface moisture, and oxygen availability, which influence microbial repair and regrowth. We further evaluate detection bias in culture-based methods, viability ambiguity in molecular approaches, and limitations of predictive microbiology models under freeze-thaw and high-solids conditions. We argue that frozen food safety and quality should be evaluated on the basis of post-thaw recovery potential rather than storage survival alone. Practical recommendations are provided for injury-aware detection, standardized freeze-thaw reporting, validation of analytical workflows, and control strategies across frozen food systems.”

3. 3

   Beyond the market: Food safety knowledge and practices among female household food handlers in the domestic kitchen.

   PloS one (Essuman et al.)Published Sep 2, 2026Checked Oct 17, 2026

   “However, this awareness did not consistently translate into safe practices. Only 22.5% reported that they regularly wash foodstuffs before usage, and 42.2% wash their hands before cooking. Risky behaviours were common, including tasting food with bare hands (43.8%) and using the same ladle throughout cooking (31.1%). Additionally, 60.1% were unaware of the correct freezer temperature (-18°C). Educational level was the only factor significantly associated with food safety knowledge (p = 0.001) and remained the sole independent predictor after logistic regression adjustment (adjusted OR 3.66, 95% CI 1.72-7.79, p = 0.001 for tertiary versus primary-educated respondents). A clear gap exists between food safety knowledge and practice among female household food handlers in Ho Municipality. Targeted, practical, and culturally appropriate interventions that promote behaviour change, rather than awareness alone, are needed to reduce preventable food-borne illness, particularly among children.”

4. 4

   Dataset of temperature and relative humidity measurements in domestic refrigerators in Bangkok Thailand.

   Data in brief (Paviet-Salomon et al.)Published Jun 4, 2026Checked Oct 17, 2026

   “This high-resolution dataset provides valuable insights into the thermal and hygrometric conditions of domestic refrigeration systems under real household usage conditions. The data may support a wide range of applications, including the assessment and optimization of refrigeration performance through analysis of temperature heterogeneity and thermal behavior inside refrigerating compartments, the evaluation of food safety and risks associated with domestic storage temperatures, the identification of potential temperature abuse conditions in challenge-test studies, the development of consumer recommendations, the development and validation of simplified thermal models and CFD simulations for predicting airflow and heat transfer within domestic refrigerators, studies related to energy consumption and food preservation, and the optimization of domestic refrigerator design parameters using CFD and artificial neural network approaches. The dataset is expected to provide valuable insights for researchers, stakeholders, and policymakers working on refrigeration technologies, food safety, and cold-chain management.”

5. 5

   Assessing vaccine cold chain storage and transport in Ukraine: a cross-sectional study.

   BMC health services research (Gaievskyi et al.)Published Mar 10, 2026Checked Oct 17, 2026

   “A total of 72040.1 h were recorded from July 2024 to October 2024 across 48 distribution routes. The recorded temperature ranged from − 13.6 °C to + 28.4 °C. The level of compliance with the recommended temperature range varied by immunisation supply chain level and across facilities at a given level. The highest compliance (~ 100%) was observed at national and oblast stores and during transits between these levels. At the same time, the lowest compliance (88.8%) during storage was observed at primary healthcare centre (PHC) sub-offices, with three of such facilities failing to maintain the recommended range at any point during the study. Additionally, 20 freeze and five heat alarms were recorded at this level, indicative of prolonged exposures. While Ukraine’s vaccine cold chain system is effective at higher levels, temperature excursions were common at lower levels, particularly in PHC sub-offices and during transport to lower-level facilities. Equipment malfunctions, gaps in knowledge and lack of procedures, compounded by power outages and lack of power supply contingencies, are probable causes.”