Shelf Life of Flaxseed Oil After Opening
Flaxseed oil should be consumed within 6 months after opening when stored properly in a cool, dry place protected from light, as it is highly susceptible to oxidation due to its high polyunsaturated fatty acid content. 1
Storage Requirements and Shelf Life
Flaxseed oil is particularly vulnerable to oxidation because of its high content of alpha-linolenic acid (an omega-3 fatty acid). To maximize shelf life after opening:
- Store in a cool, dry place protected from light and dust 1
- Keep containers tightly closed when not in use 1
- Seal caps with adhesive tape to prevent moisture exposure 1
- Refrigerate after opening to slow oxidation processes 1
- Use dark, airtight containers to protect from light 1
Factors Affecting Shelf Life
Chemical Composition
Flaxseed oil contains high levels of polyunsaturated fatty acids that readily undergo oxidation when exposed to:
Signs of Deterioration
Discard flaxseed oil if you notice:
- Rancid or off odors
- Bitter taste
- Cloudy appearance
- Thickened consistency 3
Preservation Methods
Antioxidant Addition
Adding antioxidants can help extend shelf life:
- Vitamin E (alpha-tocopherol) is commonly added, though research shows it may have pro-oxidant effects at certain concentrations 2
- Other effective antioxidants include tannic acid and ascorbyl palmitate 2
- Commercial products often contain antioxidants to improve stability 1
Temperature Control
- Refrigeration significantly slows oxidation processes
- Room temperature storage accelerates degradation
- Studies show that oils stored at 25°C, 40°C, and 60°C show progressively faster oxidation rates 2
Research Findings on Stability
Research on commercial flaxseed oils has shown:
- After 3 months of refrigerated storage (end of typical shelf life), oils show:
- 9-26% reduction in oxidative stability
- 18-40% increase in acid value (indicating hydrolysis)
- 16-37% increase in peroxide value
- 13-41% increase in anisidine value 3
Processing Considerations
Vacuum steam-pasteurization has been shown to reduce microbial contamination in flaxseed products without significantly affecting chemical stability 4. This processing method may help extend shelf life while maintaining nutritional quality.
Health Considerations
When consuming flaxseed oil, be aware that:
- Oxidized oils may have reduced health benefits
- Flaxseed oil has been associated with increased bleeding risk in some individuals 1
- Those taking antiplatelet or anticoagulant medications should use caution 1
Remember that whole flaxseed products have longer shelf life than extracted oil due to the protective seed coat and natural antioxidants present in the whole seed 5, 6.