Fingerprinting the emissions of volatile organic compounds emitted from the cooking of oils, herbs, and spices

Abstract

Emission rates for volatile organic compounds (VOCs) have been quantified from frying, spice and herb cooking, and cooking a chicken curry, using real-time selected-ion flow-tube mass spectrometry (SIFT-MS) for controlled, laboratory-based experiments in a semi-realistic kitchen. Emissions from 7 different cooking oils were investigated during the frying of wheat flatbread (puri). These emissions were dominated by ethanol, octane, nonane and a variety of aldehydes, including acetaldehyde, heptenal and hexanal, and the average concentration of acetaldehyde (0.059–0.296 mg m⁻³) and hexanal (0.059–0.307 mg m⁻³) measured during the frying was 2–10 times higher than the recommended limits for indoor environments. Total VOC emission rates were greatest for ghee (14 mg min⁻¹), and lowest for groundnut oil (8 mg min⁻¹). In a second series of experiments, 16 herbs and spices were individually shallow-fried in rapeseed oil. Over 100 VOCs were identified by offline gas chromatography-mass spectrometry (GC-MS), and absolute emission rates as well as oxidant reactivity for a subset of four spices were determined. These experiments allowed distinct indoor air quality profiles to be calculated for individual oils, herbs and spices, which were used to inform and interpret more realistic cooking experiments where a full recipe of chicken curry was prepared. Total-mass VOC emissions from chicken curry were dominated by methanol (62%), monoterpenes (13%) and ethanol (10%). Additionally, a clear relationship between the cooking events and the chemical classes of VOC was observed, e.g. heating the oil (aldehydes), frying spices (monoterpenes) and adding vegetables (alcohols).