Study of Lability and Kinetics of the Main Carotenoid Pigments of Red Pepper in the De-esterification Reaction

Different concentrations of potassium hydroxide in methanol were used to control the time required for complete de-esterification of the carotenoids present in paprika oleoresin, and the effectiveness of the overall process was determined. With concentrated solutions of potash, 20% and 30% (w/v), the reaction was completed in a shorter time but the overall process was less effective. Solutions of low concentration, 5% and 10% (w/v), enabled the kinetic study to be carried out and the rates of de-esterification for individual pigments to be compared. The effect that the fatty acid esterifying each carotenoid had on the reaction was deduced. The pigments esterified by long-chain fatty acids had a higher rate of de-esterification than those bonded with short-chain fatty acids.