Research project

Storing chilled foods at incorrect temperatures

Storing chilled foods at an incorrect temperature is a food safety risk, as it promotes the growth of harmful bacteria.

Area of research interest: Behaviour and perception

Project status: Completed

Storing chilled foods at incorrect temperatures report (462.13 KB)

Summary

FSA guidance states that the fridge should be 5°C or below. Specifically, for FBOs in England, Wales and Northern Ireland it is a legal requirement to store cold foods below 8°C.

65 households^(footnote) in the Kitchen Life 2 (KL2) study had a fridge/freezer thermometer installed during the fieldwork period. In 34 households, the average^(footnote) fridge temperature measured was greater than the recommended maximum of 5°C. 8 households had an average fridge temperature above 8°C, where the potential for bacterial growth is significantly elevated.

29 food business operators^(footnote) (FBOs) in the KL2 study had a fridge thermometer installed (28 had a freezer thermometer) during the fieldwork period. In 8 FBOs, the average fridge temperature measured was greater than the recommended maximum of 5°C, and 1 FBO had an average temperature above the legal maximum of 8°C.

Overall, the influences on the storage of chilled foods at incorrect temperatures differed across households and FBOs.

In households, the key influences were:

the fridge design, and specifically whether the fridge had a built-in thermometer and/or alarm or whether it only had a coldness dial^(footnote). (Physical opportunity).
participants not knowing or being uncertain about the recommended operating temperature for a fridge. (Psychological capability).
an absence of any routines to check the fridge temperature (Automatic motivation).

These were reinforced by the following contextual factors^(footnote):

a belief that the fridge was set to the correct operating temperature (Reflective motivation).

In FBOs, the key influences were:

the lack of a ‘compliance culture’ in certain FBOs (Social opportunity).
inconsistent routines for temperature checks on appliances (Automatic motivation.)
for a small number of FBOs, the use of older fridges that did not have thermometers or alarms built into them (Physical opportunity).

These were reinforced by the following contextual factors^(footnote):

beliefs about the consequences of fridges running at an incorrect temperature – specifically that fluctuations in temperature (above the recommended threshold) were not of significant concern for a minority of FBOs (Reflective motivation).
concerns about the food safety risks to their customers, as well as the reputation of their business (Reflective motivation).

Behaviours to target for potential interventions

In both households and FBOs, the desired practice (that is, the behaviour that households and FBOs should do to improve food safety is to check the operating temperature of a fridge (daily for FBOs) and, as required, adjust the appliance settings to ensure foods are refrigerated within the recommended range of 0-5°C.

Households need an easy way to monitor and change their fridge temperature, so interventions should focus on easy ways of doing this behaviour. For households with built-in fridge alarms, enabling consumers to set these alarms correctly (and check that they are working) could also be an area for future behavioural interventions research. Improving consumer awareness of the correct fridge temperature, and risks of running the appliance at the incorrect temperature, are also an important finding from this research. However, improving awareness alone is unlikely to improve the behaviour.

For FBOs, a focus on compliance is important, by emphasising or strengthening a requirement to undertake and record daily checks on fridge and freezer temperatures. Interventions could focus on the need to act if a fridge was above 5°C to ensure temperatures remain under 8°C.

Background

Chilling food correctly helps to stop the growth of harmful bacteria and helps food stay safe and fresh for longer^(footnote). The literature review conducted as part of the KL2 project highlights wide differences in household fridge operating temperatures^(footnote). A UK study showed fridge temperatures ranged from −1.72°C up to 17.98°C, with no fridge within the correct operating temperature throughout the entire study and only 5% of fridges within the temperature guidelines for 80% of the study duration^(footnote).

In a US study, 48% of homes had a fridge with operating temperatures above 5°C, with 11% having temperatures over 7.28°C. This research also showed that homes with fridges that tested positive for listeria and faecal coliforms had higher mean operating temperatures^(footnote).

FSA’s Food and You 2 survey found that 65% of UK consumers knew the correct temperature that a fridge should be, and 59% of respondents stated that they monitor fridge temperatures^(footnote). However, fewer than one-third of households had a thermometer in their fridge, and there may be confusion between the temperature and the coldness dial inside the fridges^(footnote). Storing chilled foods at incorrect temperatures was an area of interest for the FSA Risk Assessment team and was identified as high risk. The FSA was keen to gain insight into whether and how a fridge was checked to be cold enough and whether participants knew the safe operating temperatures for fridges.

Fridge and freezer temperature data were collected for households and FBOs involved in KL2. Participants were sent separate fridge and freezer thermometers during the fieldwork period and were asked to place them inside the respective appliances. For participants with more than one fridge or freezer, the main appliance used to chill raw foods was selected. The thermometers stored, on the device, a record of the appliance temperature every 15 minutes during the 5-day fieldwork period. This data was then downloaded from the device after it was returned to the research team. Three days of temperature data were analysed from each kitchen; corresponding to the three days that the filmed footage was analysed. For further information on the use of thermometers during the KL2 fieldwork, see the technical report.

This chapter uses the KL2 data to understand the operating temperatures of fridges in the study, whether and how fridge temperatures were checked, the factors affecting this and identify behaviours that could be the focus of future interventions research.

There are several behaviours that can influence whether chilled foods are stored at the correct temperature. This includes the temperature the fridge or freezer is set to, whether space is left inside the appliance for cold air to circulate, and whether the appliance door is frequently left open.

While not the focus of this report, data and insights were collected on the time a fridge door was left open, which has the potential to increase the operating temperature^(footnote).

Overall, leaving a fridge door open was:

observed on 463 meal occasions (44% of all meal occasions) in households, with an average duration of 48 seconds and a maximum duration of 8 minutes and 26 seconds
observed on 102 meal occasions (33% of all meal occasions) in FBOs, with an average duration of 43 seconds and a maximum duration of 4 minutes and 50 seconds

Leaving a fridge door open was an unconscious and habitual behaviour that household and FBO participants were unaware of doing. When asked in interviews, participants did not believe they left fridge doors open for more than 30 seconds (which they believed was a safe period), despite frequently being observed to do so.

Being distracted when taking items from a fridge was a significant factor in leaving the fridge door open, especially for FBOs. Though not common, certain household participants also mentioned that the seal on the fridge door (especially on new fridges) made them hard to close and reopen, meaning they would purposefully leave the door ajar for a while when loading or unloading a fridge. This was not mentioned by FBOs.

FSA guidance on storing chilled foods at the correct temperature

FSA guidance for households on storing chilled food safely includes the following advice:

store any food with a use-by date, as well as cooked dishes, salads and dairy products, in the fridge
keep chilled foods out of the fridge for the shortest time possible during preparation
cool cooked food quickly at room temperature and place it in the fridge within 1 to 2 hours
check the fridge is cold enough using a fridge thermometer as the dials on fridges don’t always show the right temperature – the fridge should be 5°C or below
do not overfill the fridge, to leave space for air to circulate and maintain the set temperature

In terms of freezing, the same guidance highlights that households should freeze pre-packaged food until midnight on the 'use by' date, with leftovers and homemade goods frozen as soon as possible. It also highlights the need to cool any warm dishes before putting them in the freezer. The guidance also says the cold temperatures of a domestic freezer (-18°C) delay chemical reactions within foods and put any bacteria that may be present on pause.

FSA guidance for FBOs on chilling foods is similar to that for households. The guidance highlights that the following foods need to be chilled:

food with a use-by date
cooked dishes
other ready-to-eat foods such as prepared salads and desserts

The FBO guidance also states the need to:

follow storage instructions
put food that needs to be chilled in the fridge straight away
cool cooked food as quickly as possible and then put it in the fridge
keep chilled foods out of the fridge for the shortest time possible during preparation
check regularly that the fridge and display units are cold enough (5°C or below)

The FBO guidance includes the need to refrigerate or dispose of any cold foods that are left out for serving or display after 4 hours. It also cites recommended fridge temperatures of 5°C or below, and a legal requirement to store cold foods below 8˚C.

For frozen foods, the guidance states that fresh foods must be frozen before midnight on the use-by date and re-labelled correctly. It also states that FBOs need to keep frozen foods at a temperature of -18˚C.

Kitchen Life 2: Findings for households

Quantitative observations from filming

In the sample of 70 households, fridge and freezer temperature data were collected for 65 households (with the remainder failing to install the thermometer during the fieldwork period).

The FSA recommends a fridge temperature of 5°C or below. Data collected in KL2 shows that:

the average^(footnote) fridge temperature of all households in the sample was 5.3°C (with minimum and maximum temperatures ranging from −3.8°C to 17.2°C).
34 households had an average fridge temperature greater than the 5°C recommended maximum during the fieldwork period.
8 households had an average fridge temperature greater than 8˚C, which poses a significant risk for elevated bacteria growth.

The FSA recommends a freezer temperature of -18°C or below. KL2 data shows that:

the average freezer temperature of all households in the sample was −19.6°C (with minimum and maximum temperatures ranging from −32.6°C to 14.4°C)
21 households had an average freezer temperature above −18°C during the fieldwork period.

KL2 data indicates that storing chilled foods at an incorrect fridge temperature was a potential safety issue for just under half the households in the sample. Additionally, the storage of frozen foods at an incorrect freezer temperature impacted just under a third of households. Whilst this is not necessarily a food safety risk (as pathogens can only grow above -2°C), freezers that fall outside of the recommended range could compromise food quality and result in spoilage. Factors influencing the storage of chilled foods at incorrect temperatures are now explored in more depth.

Factors influencing the storing of chilled foods at incorrect temperatures in households

Summary

Overall, the storing of chilled foods at incorrect temperatures in households was influenced by a reliance on fridges to work effectively and the belief that the fridge was operating at the correct temperature. A lack of routines to check fridge temperatures and (for some households) the lack of an easy means to measure the temperature, compounded by a poor understanding of the correct temperature range, also enabled the behaviour. A summary of the influences on behaviour by COM-B domain is given in figure 1.

Figure 1. Summary of COM-B factors influencing the storing of chilled foods at incorrect temperatures in households

Capability

Physical: Eye conditions were a minor influence on the storing of chilled foods at the incorrect temperature
An inability to read the fridge temperature or coldness dial due to an eyesight condition was cited as a problem for only a few participants. Such conditions only had a minor role enabling the storing of chilled foods at incorrect temperatures.

Psychological: Limited knowledge of the recommended fridge operating temperature was a significant enabler of the storing of chilled foods at the incorrect temperature
In interviews, participants commonly cited temperatures around 6°C as the safe operating temperature of a fridge (above the 5°C recommended maximum). Consequently, poor understanding of safe fridge temperatures was an enabler of storing chilled foods at incorrect temperatures.

Opportunity

Physical: Presence of a thermometer and/or alarm was a notable influence, and both encouraged and discouraged the storage of chilled foods at the incorrect temperature. The presence of a built-in thermometer and alarm and whether these were set to the right temperature, encouraged the storage of foods at the correct temperature. However, the absence of these, and if they were working correctly, was an enabler of storing chilled foods at incorrect temperatures.

Social: Social norms were not a factor. Discussions about fridge temperatures, or shared household behaviours concerning the monitoring of fridge temperatures, were not observed during fieldwork. Consequently, social norms were not an influence on the behaviour.

Motivation

Reflective: Belief that the fridge was set to the ‘right temperature’ was both a barrier and enabler to storing chilled foods at incorrect temperatures. Beliefs that fridges were already set to a safe temperature and operating effectively was very common. Where appliances were set to an incorrect temperature, this was a significant enabler of the behaviour. While participants believed that there was a high risk of foodborne illness from incorrectly chilled food, this only influenced storing food in a fridge but did not influence whether participants checked that chilled food was stored at the correct temperature.

Automatic: Automatic motivation was a enabler of the storing of chilled foods at the incorrect temperature. Overall, fridge temperatures were not routinely thought about by participants and there was an absence of any routines to check fridge temperatures. This enabled storing of chilled foods at incorrect temperatures. There were minor instances of using sensorial cues, such as hand feel, to instinctively judge whether food was cold enough.

Detailed findings

Physical capability
Physical capability was a minor factor influencing the storage of chilled foods at an incorrect temperature, and whether and how a fridge was checked to be cold. Specifically, the inability to read the fridge temperature or coldness dial settings due to an eyesight condition was cited as a problem for a few participants.

Psychological capability
Limited knowledge of the recommended fridge operating temperature was a significant enabler of storing chilled foods at incorrect temperatures.

While from the survey, 44 (out of 70) participants correctly identified the recommended operating temperature range for a fridge was between 0–5°C (see figure 2) there is strong evidence from the interviews to suggest this level of knowledge is overstated, and participants guessed, or were prompted by answers in the survey from a list of options.

Figure 2. Understanding of safe fridge operating temperature range among households (n=70)

Figure 2: Understanding of safe fridge operating temperature range among households

In interviews, participants (including those who gave correct answers in the survey) were either unsure or struggled to recall the correct fridge operating temperature, with a temperature of 6°C often cited.

I think it’s between… I can’t remember exactly, but I think it might be between 5 and 8 degrees. Okay, I might be wrong. But I think it’s that. I think mine’s set at 6 degrees.

Female, 26–40, White, socio-economic group ABC1, lives with family

Overall, participants either did not know or were uncertain about the recommended operating temperature for a fridge.
Additionally, although not commonly mentioned, some participants with fridge coolness dials were not clear about the level to which the dial should be set.

Physical opportunity
The default temperature setting of the fridge played a notable role in influencing the storing of chilled foods at incorrect temperatures in households. In interviews, participants mentioned they would only very occasionally adjust the fridge settings.

I've never really look about the limits. I definitely can set the temperature and have done it once.

Female, 26–40, White, socio-economic group ABC1, lives with family

Consequently, if the default setting was too high, foods would be stored at the incorrect temperature, and not subsequently checked.

Related to this, in interviews for households that had fridge alarms^(footnote), these were reported as being relied upon to warn if the temperature went above a safe threshold.

There’s no risk that the fridge will go below a temperature because the fridge alarm will sound it this happens.

Male, 26–40, White, socio-economic group ABC1, lives with family

Several households claimed that alarms were present in their fridge, which would sound if the temperature of the fridge was too high. However, there were only a few observations of fridge alarms sounding during fieldwork, despite KL2 thermometers indicating that fridges ran at more than 5°C for at least one hour in 52 households. It is possible that the temperature threshold for the fridge alarm had been set too high in certain households, or that the alarm was not working correctly. It is also possible that participants misunderstood the purpose of the in-built alarm (as discussed in the reflective motivation section), or inaccurately reported there was a temperature alarm on the appliance. The presence of alarms in fridge/freezers was not corroborated.

For participants who reported that their appliance did not have an alarm or built-in thermometer, there was limited reliance on the coldness dial to manage fridge temperatures. Dials were not frequently mentioned in interviews, and settings were changed very occasionally. Such households did not have an easy way to check if the appliance was running at too high a temperature and were not observed to check.

Social opportunity was not a factor that influenced the storing of chilled foods at incorrect temperatures in households, and whether and how refrigerated food was checked to be cold. There were no observations of fridge temperatures being discussed during filming, nor was it cited in the context of safety for children or others in the households in interviews. If done at all, checking the fridge temperature was a private behaviour.

Reflective motivation

Reflective motivation was both a barrier and enabler to storing chilled foods at incorrect temperatures in households and whether and how refrigerated food was checked to be cold. There were 3 influential beliefs.

First were beliefs about the consequences of storing foods at an incorrect temperature. Participants believed there was a strong likelihood of getting ill from foods that were not refrigerated correctly, especially raw foods such as meat and fish. While this view was very widespread, it was only an enabler of keeping chilled foods in a fridge, rather than checking whether the fridge was operating at a safe temperature.

Second, and related, a belief that the fridge was already set to the right temperature and was operating correctly was very common. This belief was one of the most significant factors enabling foods to be stored at an incorrect temperature. For households without a built-in fridge thermometer, participants believed the fridge was at a safe temperature as the dial was ‘set to the coolest setting’. During interviews, there were no instances of participants saying they were concerned their fridge was too warm. The belief that the fridge was already set to the correct temperature was also perpetuated by the belief that an alarm would sound if the temperature was too warm. Despite this belief, most appliances that were running too warm during the KL2 study did not sound an alarm (this issue is also discussed in physical opportunity). The presence of alarms in fridge/freezers was not corroborated.

Third, while less common, there was a belief that when problems arose with fridges, they were commonly associated with the appliance being too cold rather than too warm. For example, the build-up of ice in the freezer compartment of smaller fridges was believed to mean that the fridge or freezer was running cold, rather than the appliance not working properly. This belief also enabled foods to be stored at an incorrect temperature.

Automatic motivation

Overall, fridge temperatures were not routinely thought about by participants and consequently there was little conscious motivation to check the temperatures. The default behaviour was not to check the appliance unless a problem had arisen. There was an absence of any routines to check fridge temperatures in households, with no observations of temperature checks being undertaken during filming or stated during interviews^(footnote). In this context, automatic motivation had the potential to be a significant enabler of the storing of chilled foods at incorrect temperatures.

In one household where the participant worked in a food business and had to check fridge temperatures daily whilst at work, they did not consider the need to perform similar checks on the fridge at home.

At work, we have to record every day on the temperature of the fridge and the temperature of the freezer. But at home you would never think of it,

Female, 41–50, White, socio-economic group C2DE, lives with family

There were minor instances of participants saying they would rely on sensorial cues, such as whether milk from the fridge felt warm to the hand, to instinctively perceive whether a fridge was operating at the incorrect temperature. While this was an enabler of checking refrigerated food was cold, the behaviour was reported in a household where the fridge was running on average above 5°C across the filming period, so this approach is unlikely to be effective.

Case study

Storing chilled foods at incorrect temperatures in households

Name: Jean
Age group: 26–40 years
Household composition: Lives alone

Jean is self-employed and lives in North East England. She describes herself as ‘quite spontaneous’. While Jean enjoys cooking from scratch and experimenting with new dishes, she is also just as happy to get a ready-to-eat meal from a supermarket. She used to eat out a few times a week but was very unwell during the COVID-19 pandemic and now spends more time at home.

Jean’s kitchen is small and clean, with an open-plan layout that leads into a sitting room. Jean has a large fridge-freezer, which looks to be relatively modern and well maintained. Jean does not report any physical barriers to using the appliance.
While Jean stated in the survey that the correct temperature of the fridge should be 0–5°C, she is uncertain in the interview and believes 6°C is a good temperature. She thinks (but is not sure) that this is the temperature her fridge is set at and believes an alarm would sound if the fridge was too warm. However, she is unsure whether the alarm had been disabled after there was a problem with the freezer a few weeks ago. She also believes that because her house is old and cold, food would not get too warm anyway. She says, ‘technically you could forget to put your milk away, and your milk would be fine, because it’s so cold in the house’.

Jean’s fridge temperature data, captured by KL2 thermometers, show the appliance is consistently running too warm, with an average temperature of 6.6°C taken across 3 days (with a minimum of 3.4°C and maximum of 9.1°C). Jean is unaware of this and believes the fridge is fine as it is ‘relatively new’.

Jean knows there is a risk related with running the fridge too warm, saying ‘there would obviously be a risk from these things’. Nonetheless, she thinks the appliance is working well and, if anything, is running too cold after there was a build-up of ice in the freezer (Jean’s freezer was running at an average temperature of -17.1°C).

Analysis of Jean’s behaviour

The influences on Jean’s behaviour is primarily related to psychological capability. Firstly, Jean has a lack of knowledge on the safe operating temperature of the fridge, and falsely assumes that the ice-build up in the freezer means that the fridge-freezer is cold enough to store food at (psychological capability). This is a barrier to operating her fridge at the recommended temperature. Further, Jean relies on the alarm in the fridge-freezer to sound if the temperature is too warm, however it is not certain if the alarm works. The alarm not working is a barrier to ensuring that Jean’s fridge-freezer is operating at the recommended temperature (physical opportunity).

Identifying behaviours for interventions (households)

In reviewing the KL2 findings, a notable influence on storing chilled foods at incorrect temperatures in households was how infrequently participants considered the behaviour. One of the key observations was that participants believed once their fridge was set up, the appliance would keep foods at a safe temperature and there was limited need to check this. Where available, fridge alarms were seen to warn participants in the event of temperatures becoming too high (although KL2 data indicates this did not happen in practice).

After KL2 fieldwork was completed, a workshop was held with experts in food hygiene and the behavioural sciences to discuss the COM-B influences on each of the KL2 priority behaviours, including the storing of foods at incorrect temperatures. In the workshop, experts discussed the findings from KL2 to explore the ‘problem behaviours’ that occurred in kitchens and then considered the ‘desired practice’; that is, the behaviour that households and FBOs should do to improve food safety. In this case, the desired practice is for individuals in households to check the operating temperature of a fridge and, as required, adjust the appliance settings to ensure foods were refrigerated within the recommended range of 0-5°C.

Once the ‘desired practice’ was established, the workshop then explored the specific behaviours to target, to enable the desired practice. Each of these specific behaviours is explored in more detail below. It should be noted that the workshop was not designed to explore behavioural interventions, as this was outside of the scope of KL2. These specific target behaviours could be used in future research, for the development of behavioural interventions.

Specific behaviours to target to achieve the desired practice:

1) Checking the operating temperature of the fridge.

Findings from the KL2 study indicate that most households do not routinely check fridge temperatures and that most participants believed that their fridge was running at a ‘safe’ temperature. Consequently, enabling people to check the fridge temperature was an important behaviour to enable.
A barrier identified was that participants who owned fridges without in-built thermometers were not easily able to check the operating temperature of their appliance.
Enabling participants to check the temperature of their fridge regularly and have a reliable method in place to do so, should be a high priority area of focus for any future interventions research. Interventions should consider ways that consumers can easily check the temperature of their fridge.

2) Enabling households to lower the fridge temperature if above 5°C.

In addition to checking the fridge temperature, households need to lower the fridge temperature if it is above 5°C.
While fridge coolness settings were found to be confusing by a few participants, the ability to adjust the fridge temperature settings was not cited as an issue in most households in interviews.
Both behaviours (checking fridge temperatures and changing the temperatures as required) would need to be considered for any intervention design to achieve the desired practice.

3) Setting and checking fridge alarms

KL2 showed that many participants, who had an alarm in their fridge, relied on the sound of an alarm to alert them if the fridge temperature was too high. However, most fridges in the study did not sound an alarm, despite being too warm. Most participants assumed that the temperature of the fridge was correct if the alarm did not sound.
Enabling participants to set these alarms correctly (and check that they are working) could also be an area for future behavioural interventions research. Interventions could also focus on the effect that alarms have in alerting participants to an issue with their fridge temperature.

Further recommendation: Improving awareness of the correct fridge temperature

A key part of the FSA’s role is to provide guidance to businesses and consumers on food safety practices. KL2 has identified areas where the FSA’s guidance could be improved, or where awareness of the guidance may be beneficial.

Findings from the KL2 study indicate that many participants do not know the recommended operating temperature for their fridge. Although the majority were able to identify the correct temperature in a survey setting (where multiple-choice answers were available), they could not accurately report the correct temperature in interviews, and often guessed at ‘about 6°C’.

Improving consumer awareness of the correct fridge temperature, and risks of running the appliance at the incorrect temperature are also an important finding from this research. However, it should be noted that improving awareness alone is unlikely to improve the behaviour. For this reason, the FSA should consider improving awareness in addition to the behaviours outlined above.