Sesame oil is a cooking oil extracted from sesame seeds. Its compounds are sensitive to external conditions, and improper storage and expired shelf life can cause the molecules to oxidize, or develop rancidity. It's important for you to prevent rancidity to preserve the flavor of sesame oil and protect your health.
Sesame Oil Types
Several types of sesame oil exist and have varying degrees of vulnerability to rancidity. Unrefined sesame oil, which is the least processed type, contains the purest form of sesame seed's phytochemicals that confer health benefits. The plant compounds' vulnerability to environmental factors that cause rancidity is relatively high. The removal of plant compounds from cooking oil is called refining. It improves the temperature tolerance of sesame oil and reduces the probability of rancidity, but it also removes nutrients.
Factors That Influence Rancidity
The storage of sesame oil protects its integrity more than other factors. Placing it in the refrigerator and keeping it for only six months prevent it from becoming rancid due to storage, according to the Ohio State University Extension Service's Fact Sheet "Pantry Food Storage." A dark glass or opaque bottle keeps light from penetrating the oil and degrading the compounds.
Signs of Rancidity
Rancid oil tastes and smells slightly different than fresh oil, but no simple test is available to ensure its freshness. Proper storage and adherence to shelf-life guidelines are the best practices to follow. If the expiration date is approaching and you can't determine the sesame oil's freshness, discard it to avoid potentially toxic health effects.
Rancid Oil and Health
Fresh sesame oil provides antioxidants that protect the human body against toxins, but when it becomes rancid, it has the opposite effect. It becomes a toxic substance that causes damage. A study of rats completed by researchers at Kobe-Gakuin University in Japan and published in the "Journal of Oleo Science" in 2008 showed that liver damage may be a consequence of consuming rancid oils.
- The Ohio State University Extension; Fact Sheet Family and Consumer Sciences: Pantry Food Storage; Lydia Medeiros, et al., et al.
- "The New Food Lover's Companion"; Sharon Tyler Herbst, et al.; 2007
- "Journal of Oleo Science"; Chemical Properties and Cytotoxicity of Thermally Oxidized Oil; Nagao Totani, et al.; 2008
- Dr. Ben Kim; Experience the Health Benefits of Sesame; Dr. Ben Kim; September 2008
- Spectrum Organics: Refined or Unrefined