Air-frying prevails in tests on indoor pollutant production

Air fryers are the least polluting cooking method by far, a new analysis by a team of environmental scientists and chemists has confirmed.

The researchers, led by the University of Birmingham in the UK, cooked chicken breast in a well-controlled research kitchen by pan-frying, stir-frying, deep-fat frying, boiling and air-frying, and they measured the levels of particulate matter and volatile organic compounds (VOCs) emitted by each technique. Peak concentrations of indoor VOCs for pan-frying were 260 parts per billion (ppb), compared with 230ppb for deep frying, 110ppb for stir-frying, 30ppb for boiling and 20ppb for air-frying. In terms of peak concentrations of particulate matter, the team found that pan frying using an induction hob led to 92.9 micrograms per cubic metre (µg/m³) of air, compared with 26.7µg/m³ for stir-frying, 7.7µg/m³ for deep frying, 0.7µg/m³ for boiling and 0.6µg/m³ for air-frying.

Unsurprisingly, oil-based cooking methods produced far more particulate matter and VOCs than water-based techniques, which the researchers attribute to the Maillard reaction between amino acids and reducing sugars that gives browned food its distinctive flavour. The key VOC species emitted from the three frying methods were aldehydes, ketones, furans, aromatic hydrocarbons, alkenes, pyrazines and alkanes.

The cooking process in these experiments only lasted about 10 minutes, but substantially higher levels of pollutants were recorded in the kitchen for well over an hour afterwards.

Several factors affect the levels of pollution from cooking alongside the method used, including the amount of oil used and the temperature of the hob, explained study lead author Christian Pfrang, an atmospheric chemist at the University of Birmingham. ‘What we can say with certainty, however, is that improving the ventilation in kitchens by opening windows or using extractor fans, will help to disperse polluting particles and reduce personal exposure,’ he said.