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Chemistry in Heated Cooking Oils and Effects on Gaseous and Particulate Emissions
Manpreet Takhar, Jenna Ditto, Eleanor Vaz, Jonathan Abbatt, ARTHUR W. H. CHAN, University of Toronto
Abstract Number: 387
Working Group: Aerosol Chemistry
Abstract
Food cooking contributes a significant fraction of volatile organic compounds (VOCs) and particulate matter (PM) in urban atmospheres. Most of these emissions originate from heated oils and food ingredients. In this work, we study the decomposition mechanisms of triglycerides as a source of gas-phase aldehydes and particles emitted from food cooking. Experiments were conducted by heating cooking oils in a temperature-controlled aluminum block. Cooking oils with different triglyceride composition were studied, along with a commercially available homotriglyceride (triolein). VOCs emitted during the heating process were measured using online (PTR-MS) and offline (GC/MS) mass spectrometry. Particle number and volume concentrations were measured using SMPS, and particles were also collected on filters for offline GC/MS analysis with derivatization. Aldehydes are formed from radical-initiated autoxidation. Antioxidants, added by oil manufacturers to increase oil shelf life, were found to suppress aldehyde emissions from oils with larger degree of unsaturation (canola oil) and promote emissions from others (triolein, olive oil, sunflower oil). This effect can be explained using a kinetic model by the relative importance of radical propagation and termination by antioxidant compounds. On the other hand, PM consisted mostly of free fatty acids. The fraction of free fatty acids in cooking oil increased with each heating cycle, consistent with increasing PM emissions. The effect of water in promoting hydrolysis of triglycerides is also investigated. Our results highlight the importance of studying cooking oil chemistry as a basis for understanding food cooking emissions and developing effective strategies for mitigating exposure.