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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Functional Foods Research » Research » Publications at this Location » Publication #381340

Research Project: Increasing Food Shelf-Life, Reducing Food Waste, and Lowering Saturated Fats with Natural Antioxidants and Oleogels

Location: Functional Foods Research

Title: NMR spectroscopy as a powerful tool for identification of polymers and other oxidation products in frying oil

item Hwang, Hong-Sik

Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/16/2021
Publication Date: 4/16/2021
Citation: Hwang, H. 2021. NMR spectroscopy as a powerful tool for identification of polymers and other oxidation products in frying oil. American Chemical Society Abstracts. Americal Chemical Society Spring Meeting. April 5-16, 2021, Virtual.

Interpretive Summary:

Technical Abstract: Although polymers are the major oxidation products accumulating in oil during frying, mechanisms of polymerization have not been well understood. Polymers along with aldehydes in frying oil are known to be associated with adverse health effects. Understanding mechanisms of polymerization and structures of polymers is critical to understand their toxicity and to develop methods to prevent their formation. An earlier study reported that Diels–Alder reaction, a long-believed mechanism for the polymerization of oil, was not the major reaction to produce polymers. In this study, we found that ester bonds are one of the chemical bonds forming polymers during frying using NMR spectroscopy. Ester value increased as soybean oil oxidized and 13C NMR spectrum showed new ester carbonyl carbon signals evidencing the formation of ester bonds. The NMR spectroscopy after the reaction of oxidized soybean oil with acetyl chloride was also employed to verify NMR signals corresponding to alcohol. By this method, proton signals at 3.61 and at 3.71 ppm, which were reported to be ether bonds forming polymers, were found to be those of alcohols produced in oil. Some uncertain assignments of proton signals of oxidized oil were clarified as signals of alcohols, several previously assigned signals as alcohols were confirmed, and a new proton NMR signal was assigned to be an alcohol. There are so many oxidation products that were not yet identified, and this study indicates that the NMR spectroscopy can be a great tool to identify oxidation products formed in oil.