Particulate matters, aldehydes, and polycyclic aromatic hydrocarbons produced from deep-frying emissions: comparisons of three cooking oils with distinct fatty acid profiles

Deep-frying, a common cooking method, releases significant particulate and gaseous pollutants, contributing substantially to ambient organic aerosol and posing adverse health risks, including lung cancer and respiratory diseases. Previous research indicated that oil properties, especially fatty acid composition, influence emission levels, but comprehensive comparisons across oils with distinct fatty acid profiles were lacking. This study aimed to compare particulate matter, gaseous aldehydes, and particle-bound PAHs from deep-frying using palm, olive, and soybean oils, exploring the relationship between emissions, oil quality (peroxide value, acid value, total polar compounds), and fatty acid profiles. The study's significance lies in providing a comprehensive understanding of the health impacts of different cooking oils and informing strategies to minimize harmful emissions during food preparation.

Existing literature highlights cooking emissions as a major source of organic particulate matter, contributing significantly to ambient air pollution and associated health problems. Studies have linked cooking emissions to increased risks of lung cancer and mutagenicity, particularly in non-smokers, and a higher incidence of respiratory diseases among cooks. Polycyclic aromatic hydrocarbons (PAHs) and aldehydes are recognized toxic compounds in cooking emissions, along with black carbon (BC) and ultrafine particles. While previous research suggested that oil properties affect emission levels, a comprehensive analysis of multiple pollutants across diverse oils was missing. This gap prompted the current investigation to address the knowledge limitations on oil-specific impacts on cooking emissions.

The study used a simulated kitchen environment with an electric fryer and a range hood to mimic typical household cooking conditions. Three oils—soybean, palm, and olive—were selected for their distinct fatty acid compositions. For each oil, 3.5 liters were used to fry 12 batches of French fries (175 g/batch) at 180°C. Real-time monitoring of particle number and mass concentrations, as well as BC, was performed using a scanning mobility particle sizer (SMPS), an aerodynamic particle sizer spectrometer (APS), and an aethalometer (AE33). Particle-phase and gas-phase PAHs were collected using quartz filters and XAD-2 cartridges, respectively, and analyzed by GC-MS/MS. Similarly, particle-phase and gas-phase aldehydes were collected with DNPH-coated glass fiber filters and DNPH-coated silica cartridges and analyzed using HPLC. Oil quality parameters (acid value, peroxide value, total polar compounds) were determined using standard methods. Statistical analyses, including Kruskal-Wallis test and Spearman rank correlation, were used to compare emission levels among oils and to evaluate correlations between emissions and oil characteristics.

The study revealed significant differences in emission profiles among the three oils. Palm oil produced the highest total particle number concentration ((3895 ± 1797) × 10³/cm³), predominantly in the Aitken mode (20–100 nm). This was positively correlated with palmitic acid (a major saturated fatty acid) and total polar compounds (TPC), indicating higher oil degradation. Soybean oil, rich in polyunsaturated fatty acids (PUFAs), emitted the highest levels of gaseous aldehydes (3636 ± 607 µg/m³), with concentrations significantly correlated with α-linolenic and linoleic acid percentages. Specifically, hexanal and trans-2-heptenal showed strong correlations with linoleic acid. Palm oil also emitted the highest concentration of particle-bound PAHs, with positive associations observed between certain PAHs and saturated fatty acid percentages. Olive oil consistently displayed the lowest levels of all measured pollutants. Further analysis showed that TPC was positively correlated with particle number concentration and BC concentration, suggesting that higher oil degradation leads to increased emissions.

The findings highlight the significant impact of cooking oil type on the emission of harmful pollutants during deep-frying. The positive correlations between saturated fatty acids and particulate matter, and between PUFAs and aldehydes, confirm the influence of fatty acid composition on emission profiles. The high levels of particle-bound PAHs from palm oil raise concerns regarding potential health risks. The lower emission levels from olive oil suggest its potential as a healthier cooking option compared to soybean and palm oils. These results emphasize the importance of considering oil selection to reduce cooking emissions and mitigate associated health risks. Future research should investigate the mechanisms underlying the formation of specific pollutants from different fatty acids and explore strategies to minimize emissions through oil processing or cooking techniques.

This study demonstrates that the fatty acid composition and quality of frying oils significantly influence the generation of harmful emissions during deep-frying. Soybean oil produced the highest levels of gaseous aldehydes, while palm oil emitted the most particle-bound PAHs. Olive oil showed consistently lower emissions of all measured pollutants. These findings highlight the importance of oil selection in reducing cooking-related air pollution and potential health risks. Future research could investigate the effectiveness of different filtration methods and alternative cooking techniques in minimizing these emissions.

The study was conducted in a simulated kitchen environment, which may not perfectly replicate the conditions of real-world kitchens. The limited number of oils and food types used may affect the generalizability of the findings. More research is needed to evaluate the influence of other factors such as cooking temperature, ventilation, and food type on emissions.