An efficient method for a numerical description of virgin olive oil color with only two absorbance measurements

Four polynomial expressions are obtained that provide a good approximation and an easy, rapid calculation of the chromatic coordinates and the chroma— L * , a * , b * , and C —for the illuminant C and the standard observer, for a virgin or extra virgin olive oil; absorbance is measured at only 480 and 670 nm. These are as follows: L * =0.556458(A 480 ) 2 −2.51145A 480 +0.55504(A 670 ) 2 −8.53016A 670 +98.4089; a * =0.177372(A 480 ) 2 +2.1363A 480 +1.43254(A 670 ) 2 −0.789231A 670 −13.9246; b * =−16.0277(A 480 ) 2 +79.8932A 480 −5.06558(A 670 ) 2 +3.36169A 670 +31.9405; C =−15.8439(A 480 ) 2 +78.9312A 480 −5.26784(A 670 ) 2 +3.56917A 670 +33.3927. These give acceptable results, making the method a practical alternative to the extremely laborious Commission Internationale d’Eclairage (CIE) L * a * b * system, by which 391 absorbance values must be measured individually, nanometer by nanometer, before applying more complex equations. The validity of the proposed method has been confirmed by comparison, using a set of 20 sample oils different from the set of 25 oils used to generate the order of the equations. The variations between the values provided by the proposed and standard methods, respectively, had a mean of 0.00 for each of the chromatic variables— L * , a * , b * , and C ; SD were moderate (0.71, 0.52, 1.22, and 1.22, respectively); the root mean square and the R 2 ‐terms also confirmed the validity of the method.