Higher fridge temperatures in the homes of older people could be putting them at greater risk of Listeria infection, according to a study.

Researchers looked at the temperatures of domestic refrigerators in the Netherlands and the impact on listeriosis cases related to ready-to-eat (RTE) cooked meat products.

A survey among 1,020 Dutch consumers assessed their knowledge and behavior regarding refrigerators.

The mean temperature of 534 domestic refrigerators on the bottom shelf was 5.7 degrees C (42.2 degrees F). The 24-hour profiles of an additional 50 refrigerators showed temperatures on the upper shelf were higher at 7.7 degrees C (45.8 degrees F). In the Netherlands, it is recommended that the temperature of refrigerators should be 4 degrees C (39.2 degrees F).

Outcomes of the survey were used to estimate the number of listeriosis cases per year due to consumption of RTE-cooked meat products among different population risk groups.

Fridge temp findings
The analysis of measured temperatures of 534 refrigerators on the bottom shelf showed they varied from −1 degrees C to 17 degrees C (30.2 to 62.6 degrees F), with two-thirds showing 6 degrees C (42.8 degrees F) or lower, according to the study published in the International Journal of Food Microbiology.

The survey found that only 28 percent of consumers said 4 degrees C (39.2 degrees F) was the correct temperature of a fridge. Around 8 percent indicated a lower temperature; the same amount indicated 8 degrees C (46.4 degrees F). People familiar with the recommended setting had a significantly lower temperature in the refrigerator. 

Most participants never checked the refrigerator’s temperature; 37 percent occasionally did it, and 2 percent did it regularly. 

The measured temperatures of the refrigerators of consumers aged 65 and older were, on average, higher than those of people below 35. Younger consumers were more aware of the recommended temperature. Fridges with the highest temperatures of 16 and 17 degrees C (60.8 and 62.6 degrees F) were owned by participants aged 79 and 86. Refrigerator type and age did not significantly affect temperature.

The survey showed that two-thirds of participants stored meat products on the bottom or middle shelf. The general advice is to keep RTE-cooked meat products on these two shelves.

Impact on Listeria risk
Modeling predicted an average number of 191 illnesses per year through the consumption of RTE-cooked meat products. As expected, the high-risk populations had a higher risk of listeriosis. 

Storing opened RTE cooked meat products at home for either under 7 days or at temperatures below 7 degrees C (44.6 degrees F) resulted in a significant reduction in predicted illness cases, said scientists.

An analysis was conducted on the impact of various variables on the estimated risk of listeriosis from RTE-cooked meat products. Results showed that consumer behavior, such as reducing storage time and controlling refrigerator temperature at home, can significantly reduce the risk.

Scientists said that despite recommendations being included in numerous food safety campaigns aimed at consumers, the storage temperature of chilled foods is frequently above 6 degrees C (42.8 degrees F). Contributing factors include a lack of perceived importance or risk control benefit. 

“Our study showed that the more extreme high storage conditions were found in refrigerators of the elderly, and this indicates that there is a need for more targeted communication about good storage practices that can be taken in the home kitchen,” said researchers.

“Specific advice can be given to the elderly, such as setting a maximum temperature for the home refrigerator, storing RTE cooked meat products on the bottom or middle shelf, and consuming within two to three days after opening.”