Optimization of HPLC quantification of carotenoids in cooked green vegetables—Comparison of analytical and calculated data

Data on cooked vegetables is lacking in carotenoid databases. Analysis of cooked vegetables has problems somewhat different from those of the raw produce. Although cooking makes the extraction of carotenoids easier, incorporation of oil and formation of degradation products during cooking pose analytical difficulties. Thus, a method developed for raw vegetables was optimized for cooked vegetables, particularly in the pre-chromatographic steps. In the absence of data obtained by laboratory analyses, carotenoid concentrations have been calculated from raw sample results. Since carotenoids are prone to degradation, assessment of retention or loss during cooking/processing is also needed. Multiplying the carotenoid concentrations of the raw sample by the %CCs (concentration change factors) gave the same values obtained by analyses of the cooked samples. The same concentrations could be obtained with the %TRs (true retention factors) only if the products obtained by multiplication were divided by the yield factors. The %TR correctly reflected the degradation percentage during cooking. These results are understandable, considering that weight gain or loss due to uptake or release of water, oil or food solids, must be compensated for to appraise carotenoid degradation. On the other hand, concentration changes brought about by cooking include both degradation and weight changes.