Abstract:

An ultraviolet (UV) spectrophotometric method for determining acid value (AV) of edible oils was developed
based on the stoichiometric reaction of free fatty acid with K-phthalimide to produce phthalimide showing characteristic
absorption at 290 nm. The presented prediction equations for phthalimide were validated with known and unkown samples,
and analyzed in comparison with the national standard method (iodimetry). The comparable results of AV were obtained
by both methods with determination coefficients (R2) above 0.99, indicating that the models had good prediction efficiency
which was independent of the type of oil investigated. The relative errors and relative standard deviation (RSD) for the
model-predicted values were 0.22%–6.87% and 1.34%, respectively. In conclusion, the spectrophotometric method was
characterized by good precision and accuracy. Therefore, this method is feasible for rapid determination of acid value in
edible oils.

Key words: edible oil, acid value, ultraviolet spectroscopy, determination