Want air fryer cooking instructions on pack? Here’s more detail from Greg Hooper, Instruction Services Manager on why this is such a challenge

24 November 2022 | Greg Hooper, Microwave and Thermal Process Specialist

Air fryers are excellent devices that give consumers the opportunity to reduce their energy consumption from cooking, whilst quickly delivering comparable quality and ‘crispness’ to other cooking methods with less oil / fat. Despite the popularity and success of air fryers, the variability of cooking performance currently presents a food safety barrier to cooking instruction validation for high risk foods and to displaying such instructions on back of pack.

In our last blog, we outlined the testing conducted by our Process Innovation team and Greg Hooper, Instruction Services Manager across a range of air fryer types and models. We discussed how the performance variability seen raises concerns for the current feasibility of generating, verifying and validating ‘one-size-fits-all’ instructions, which if not correct could be a food safety risk to the consumer.

Here we cover the topic and testing in more detail, as well as sharing some of our methods and data.

The importance of a verified, validated process – BRC Clause 5.2.5: Cooking (heating) instruction validation

For food safety, the generally accepted thermal process is equivalent to two minutes at 70°C because this has been proven to reduce Listeria monocytogenes numbers one million-fold and adequately reduce or eliminate levels of E.coli and Salmonella. For foods not considered ‘ready-to-eat’ we must ensure that cooking instructions facilitate the consumer achieving this thermal process equivalent so that the food is safe to eat. The BRC Global Standard for Food Safety Clause 5.2.5: Cooking (heating) instruction validation mandates that on-pack cooking instructions be fully verified and validated to ensure the instructions will deliver the required minimum thermal process using the worst case of all variables.

You can read our white paper on cooking (heating) instruction validation, within which we explain that it is impossible to validate the safety of barbeque cooking instructions due to wide differences in barbeque performance. Similarly, the Campden BRI study on air fryers indicates that this relatively new cooking method may present a similar challenge. The detail and findings of our air fryer performance study can be found in our white paper, where we also explore the implications for retailers and suppliers as well as how Campden BRI could support the industry in finding a solution. Visit our air fryers services page to explore the services we offer for air fryer cooking instructions.

Campden BRI have tested a wide range of air fryers

A study was conducted on 10 disparate domestic air fryers ranging from 800W to 1800W and including different models, types (basket, halogen, paddle) and cavity sizes.

Here is the testing plan that was used by the Instruction Services team:

Determine the actual air temperatures achieved when dials were set to 160°C, 180°C and 200°C.
Assess the difference in the dial setting when the actual air temperature was calibrated at 180°C.
Heat a PFTE cylinder shaped ‘model food’ (sausage) to 70°C in all air fryers – using both dial and calibrated temperatures.
Heat standardised chilled and frozen products of different characteristics, to achieve a minimum thermal process equivalent to 70°C for two minutes and a final minimum temperature of 70°C.
Five replicate trials were performed in each of the 10 air fryers for each of the five products.

The results demonstrated a high level of variation in air fryer performance

Our rigorous testing revealed three key findings; variation in dial temperature accuracy, variation in the time taken to achieve a safe cook and variation in the final temperature of the food. The results are summarised in the table below, and the three key findings discussed in the following three sections of this blog.

Air fryer	°C difference from actual temperature to dial setting 160 °C	°C difference from actual temperature to dial setting 180 °C	°C difference from actual temperature to dial setting 200 °C	Necessary °C adjustment to dial setting to achieve an actual temperature of 180 °C	Minutes taken to achieve 70°C Actual temperature 180 °C Model Sausage	Minutes taken to achieve 70°C Dial temperature 180 °C Model Sausage	Minutes taken to achieve 70°C for two minutes and 70°C
Air fryer							Frozen Burger Actual temperature 180 °C	Chilled Burger Actual temperature 180 °C	Frozen Hash Browns Dial temperature 200 °C	Chilled Spring Rolls Actual temperature 180 °C
Air fryer 1 Basket 7.6L 1700W	-4	-3	-4	+5	11	10	21	14	13	12
Air fryer 2 Halogen 9L 1200W 1400W	-7	-6	-6	+14	10	10	25	17	12	8
Air fryer 3 Basket 3L 1400W	-13	-15	-18	+37	10	11	25	17	14	8
Air fryer 4 Basket 4.1L 1400W	-1	+1	-4	+7	10	10	20	13	10	8
Air fryer 5 Toaster Oven 11L 1800W	-16	-18	-30	+16	10	10	20	13	12	9
Air fryer 6 Paddle 1.7Kg 1500W	-17	-20	-38	+57	11	12	17	13	13	9
Air fryer 7 Basket 4.2L 1400W	+4	-1	-3	+4	10	9	17	13	11	8
Air fryer 8 Halogen 10.6L 1300W	-1	+2	-8	+5	10	9	23	16	12	9
Air fryer 9 Basket 2L 800W	Unkown	Unkown	Unkown	Unkown	12	12	24	17	17	10
Air fryer 10 Basket 4L 1400W	+8	-1	-9	+7	10	9	18	14	11	8

Variation in dial temperature performance

With a dial setting of 160°C the actual air temperature ranged from 17°C too low (Air fryer 6) to 8°C too high (Air fryer 10).
With a dial setting of 180°C the actual air temperature ranged from 20°C too low (Air fryer 6) to 2°C too high (Air fryer 8).
With a dial setting of 200°C the actual air temperature ranged from 38°C too low (Air fryer 6) to 3°C too low (Air fryer 7).
With one air fryer, using a dial setting of 220°C only achieved an air temperature of 163°C.

Variation in the time taken to achieve a safe cook on the same product

Model Sausage (actual calibrated temperature 180°C) – 10 to 12 minutes across the ten air fryers to achieve 70°C.

Model Sausage (dial set to 180°C) – 9 to 12 minutes across the ten air fryers to achieve 70°C.

Frozen Burger (actual calibrated temperature 180°C where possible) – 17 to 25 minutes across the ten air fryers to achieve a minimum temperature of 70°C and an equivalent process of 70°C for two minutes.

Chilled Burger (actual calibrated temperature 180°C where possible) – 13 to 17 minutes across the ten air fryers to achieve a minimum temperature of 70°C and an equivalent process of 70°C for two minutes.

Frozen Hash Browns (dial set to 200°C) – 10 to 17 minutes across the ten air fryers to achieve a minimum temperature of 70°C and an equivalent process of 70°C for two minutes.

Chilled Spring Roll (actual calibrated temperature 180°C where possible) – 8 to 12 minutes across the ten air fryers to achieve a minimum temperature of 70°C and an equivalent process of 70°C for two minutes.

In the time taken for some air fryers to completely cook a product, other air fryers may not come close to the product reaching 70°C

The required final minimum temperature of 70°C was not achieved when the shortest cook time (the cook time taken for faster heating air fryers to achieve the required thermal process and final minimum temperature) was applied to slower heating air fryers.

For the frozen burger trials, out of the ten air fryers used, the longest time taken to reach a thermal process of 70°C for two minutes and a final minimum temperature of 70°C was by Air fryer 2 and Air fryer 3, both taking 25 minutes. Faster heating air fryers (Air fryers 6 and 7) took only 17 minutes to achieve this thermal process. If the shortest cook time of 17 minutes was used in the slower heating air fryers (Air fryers 2 and 3) it would have given final minimum temperatures of 45°C and 36°C.

For the chilled burger trials, the longest time taken to reach a thermal process of 70°C for two minutes and a final minimum temperature of 70°C was by Air fryers 2, 3 and 9, all taking 17 minutes. Faster heating air fryers (Air fryers 4, 5, 6 and 7) took only 13 minutes to achieve this. If the shortest cook time of 13 minutes was used in the slower heating air fryers it would have given final minimum temperatures of 62°C, 59°C and 36°C.

For the frozen hash browns, the longest times taken to achieve the required thermal process and final minimum temperature were by Air fryers 3 and 9, taking 17 and 14 minutes respectively. Faster heating air fryers (Air fryer 4) took only 10 minutes to achieve this. If the shortest cook time of 10 minutes was used in the slower heating fryers, it would have given final minimum temperatures of 31°C and 37°C.

In the time taken for some air fryers to completely cook a product, other air fryers may not come close to the product reaching 70°C"

Greg Hooper, Instruction Services Manager and Microwave Specialist

It is important to note that air fryers that heat products very quickly may not be ‘better’ than those that heat a product more slowly. Food products take time to achieve a desirable ‘cooked’ quality (e.g. browning and crisping) and just because one air fryer has achieved a safe minimum temperature (e.g. 70°C) very quickly doesn’t mean the product quality will be better than from an air fryer that has taken longer.

Implications for retailers and suppliers

Recommending a cook time based on ‘dial temperature’ may not give safe results considering the performance variation observed in the Campden BRI trials.

Greg Hooper commented,

We have tested 10 different air fryers and found considerable differences in their ability to safely cook products using one instruction, with different cook times required for the same product when using the same settings. Think of the variability that might be out there with all of the other air fryers that are available"

This variation may be a barrier to generation, verification and validation of cooking instructions, which could present risks of improper cooking and associated unsafe food. The time required to achieve safe cooking in slower heating air fryers could amount to overheated, poor quality food for the consumer, whereas cooking instructions based on faster heating air fryers could pose serious food safety risks to the consumer when used with slower heating air fryers.

Greg Hooper emphasises the impact of air fryer performance variation –

to offer an instruction verification / validation service could present food safety and quality risks"

Similar risks manifested in food poisoning cases in the 1990s, which were linked to products cooked in microwave ovens. This was associated with differing performance of microwave ovens.

It is important to understand that the wattage rating system developed for microwave ovens uses the wattage delivered to food, not the wattage used by the microwave oven. This was crucial in developing a system that would work for determining cook times that could work across the myriad of different microwave oven designs and models. The wattage rating stated for air-fryers is the wattage used by the air fryer, which will not be equivalent to the power (heat) actually absorbed by the food. For example a large capacity, poorly insulated air fryer with low air circulation speeds might use much of its 1400W supply power heating the unit and air and replacing heat losses. This may not be as efficient (fast) at heating a food as a 1400W air fryer with lower capacity, higher air speeds and better insulation, where much more of the 1400W is available for heating the food.

Are we seeing a similar problem about to evolve with air fryers? This was addressed for microwave ovens through the development of a microwave rating system. Could the development of a new rating system be an option for air fryers?

Campden BRI can help food businesses navigate the challenges posed by air fryer variability

Campden BRI can offer expert advice on this topic, as well as in depth air fryer testing. Robust scientific rigour is particularly crucial for ready-to-cook products and our service is gold standard for providing this.

Below is an example service for investigating air fryer cooking times using the wide range of air fryers selected for the recent research project:

Three air fryers at a popular power rating (1400W).
Two additional air fryers (best and worst from this project).
Perform five (or three) trials in each air fryer.
Achieve a minimum temperature of 70°C and equivalent thermal process to 70°C for two minutes.
Communicate results* to the client

Taking the frozen burger trials as an example of a product supplied by a client for instruction trials, results from the table below could be expressed as:

1400W air fryers at a calibrated 180°C

Best 17 minutes, worst 25 minutes.

All air fryers tested at calibrated 180°C

Best 17 minutes, worst 25 minutes.

Air fryer	Minutes taken to achieve 70°C for two minutes and 70°C
Air fryer	Frozen Burger Actual temperature 180 °C	Chilled Burger Actual temperature 180 °C	Frozen Hash Browns Dial temperature 200 °C	Chilled Spring Rolls Actual temperature 180 °C
Air fryer 1 Basket 7.6L 1700W	21	14	13	12
Air fryer 2 Halogen 9L 1200W 1400W	25	17	12	8
Air fryer 3 Basket 3L 1400W	25	17	14	8
Air fryer 4 Basket 4.1L 1400W	20	13	10	8
Air fryer 5 Toaster Oven 11L 1800W	20	13	12	9
Air fryer 6 Paddle 1.7Kg 1500W	17	13	13	9
Air fryer 7 Basket 4.2L 1400W	17	13	11	8
Air fryer 8 Halogen 10.6L 1300W	23	16	12	9
Air fryer 9 Basket 2L 800W	24	17	17	10
Air fryer 10 Basket 4L 1400W	18	14	11	8

* It might be tempting in the above example to suggest a cook time of 25 minutes, as it would provide a safely cooked product. However, the variability found with testing just 10 air fryers means there would be little confidence that this cook time would safely heat the product in all air fryers found in the marketplace. We should also consider that the air fryers tested in the above example were calibrated at 180°C. Based on the dial accuracy performance seen for several of the models tested here, we could expect greater variability in cook times if dial settings had been used.

Another point for consideration is the preheat time taken for the air fryers to achieve their operating temperature. All the cook time testing performed in this research project used air fryers preheated for 20 minutes, but many consumers may be using their air fryers from ‘cold’. Given that the preheat time was found to vary from approximately 5 to 20 minutes for the air fryers tested, this could lead to further issues with variation of cooking performance.

The potential food safety implications explored here relate to foods that are not considered ‘ready-to-eat’. For ready-to-heat and raw / ready-to-cook foods we must ensure that cooking instructions facilitate the consumer achieving a thermal process equivalent to 70°C for two minutes. This is so that the food is safe to eat when cooked in any of the appliances to which the cooking instructions are intended to apply.

We want to study this further and help the industry find a solution

While we are offering some air fryer instruction services, we would be particularly interested to work with our members in expanding the air fryer study, with the mission to produce safe, validated, BRCGS-compliant cooking instructions for air fryers. One option would be to develop an air fryer rating system, like used for microwaves, which would enable effective cooking instruction verification.

Please do contact Greg if this of interest, as this is the most realistic way for us to see safe, verified air fryer cooking instructions on back of packs. Campden BRI can then arrange an online meeting for all interested parties to discuss.

About Greg Hooper

Greg has worked here at Campden BRI since 1990, after studying Applied Science (Physics and Chemistry). As part of his extensive knowledge and experience in thermal processing and microwave cooking, he was instrumental in setting up the microwave heating category rating system used in the UK, and has travelled internationally assisting and advising on the safe development of microwave products and rating systems.