The quality of edible oil is of primary importance to both manufacturers and consumers, especially in deep-fried food products. During storage, processing, and repeated heating, edible oils undergo significant chemical changes, leading to the formation of degraded and potentially hazardous compounds. One of the primary indicators of oil deterioration is the formation of Free Fatty Acids (FFA).
Free fatty acids are produced by the hydrolysis of triacylglycerols (TAGs) in the presence of moisture, heat, and lipase enzymes. The extent of FFA formation depends on factors such as time, temperature, and moisture exposure. The hydrolysis reaction can be represented as:
Hydrolysis Reaction:
Triacylglycerol + 3H₂O → Glycerol + 3 Fatty Acids
As hydrolysis progresses, the concentration of FFA increases. Since FFAs are less stable than neutral triglycerides, they are more susceptible to oxidation, resulting in undesirable effects such as off-flavor development, reduced smoke point, and accelerated rancidity.
The FFA content is commonly determined by titration with a standard alkali solution (e.g., NaOH or KOH). The free fatty acids present in the oil react with alkali to form soap and water:
Neutralization Reaction:
R–COOH + NaOH → R–COONa + H₂O
The percentage of FFA (expressed as oleic acid) is calculated using the formula:
%FFA=(V×N×28.2)/W×100
Where:
V = Volume of NaOH used (mL)
N = Normality of NaOH
W = Weight of oil sample (g)
28.2 = Equivalent weight factor for oleic acid

Thus, FFA content serves as a key indicator of oil quality and commercial value, reflecting the extent of hydrolytic degradation and suitability of the oil for consumption or further processing.