Free fatty acids (FFAs) negatively affect oil quality, primarily by contributing to off-flavors.
Impact of Free Fatty Acids on Oil
Free fatty acids are released from triglycerides (the main component of oil) through hydrolysis or lipolysis. The presence of these FFAs in oil is generally an indicator of oil degradation and poor quality. The specific effects include:
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Off-Flavor Development: FFAs, especially short-chain fatty acids, contribute directly to undesirable flavors and odors in oils. These off-flavors are often described as rancid, sour, or soapy. This is the primary reason FFA content is monitored in the food industry.
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Reduced Smoke Point: A higher FFA content lowers the smoke point of the oil, meaning it will start to smoke and degrade at a lower temperature during cooking. This smoking can produce harmful compounds and further degrade the oil.
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Increased Viscosity: High levels of FFAs can increase the viscosity of the oil. This can affect its suitability for certain applications.
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Foaming During Frying: In frying oils, FFAs can contribute to increased foaming, affecting the quality of the fried product and the efficiency of the frying process.
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Deterioration Rate Acceleration: FFAs can accelerate the rate of other deterioration reactions in the oil, such as oxidation, leading to further degradation and shortening the oil's shelf life.
Measuring Free Fatty Acids
The amount of FFAs in oil is usually measured by titration with an alkali solution, using ethyl alcohol as a solvent. This determines the acidity of the oil, which is directly related to the FFA content. The result is often expressed as a percentage of a specific fatty acid (e.g., % oleic acid).
Example
Consider a batch of olive oil. If the oil is improperly stored (e.g., exposed to heat, light, or air), the triglycerides will break down into FFAs. This increased FFA content will lead to the development of a rancid flavor, making the oil less desirable for culinary use. Its smoke point will decrease making it less suited for frying.
