Correlation of High Performance Liquid Chromatography (HPLC) and Spectrophotometric Methods to Assess the Post Harvest Storage and Processing Changes in Total β-carotene Contents in Selected Nigeria Vegetables

The aim of this study was to correlate analytical methods (HPLC and spectrophotometric) in assessing the changes in total β-carotene contents in leafy vegetables during ambient temperature storage (29+2°C) and domestic processing (5 min,100°C.) The vegetables analyzed were: Telfairia occidentalis, Amaranethus hybridus, Talinum triangulare,Pterocarpus mildbraedli and Gnetum africanum. Total–carotene was determined spectrophometrically, while HPLC was used for detailed analysis of carotenoides. Lutein, β -cryptoxanthin and β-carotene isomers were identified and quantified. Results indicated that the raw vegetables were rich in lutein (124.03-655.95 µg/gdwt) and total β -carotene (45.42 – 246.93 µg/gdwt). Beta–cryptoxanthin was detected in small quantity (5.05-11 µg/gdwt). However, spectrophotometric result indicated a total–carotene content range (186.10 – 953.78 µg/gdwt). Cooking increased significantly (P< 0.05), the lutein (382. 92 – 1158.83 µg/gdwt), total β -carotene (738.53 – 1756.51 µg/gdwt) contents of the samples, however, it decreased the % trans–β-carotene contents. Storage conditions in the study increased significantly (P< 0.05) the contents of total β -carotene and total–carotene except in the case of Gnetum africanum leaf. A regression model for the two methods of analysis of β -carotene with a coefficient of correlation r = 0.925 and coefficient of determination r2 = 0.856, which allows for the calculation of total β - carotene from total-carotene content was obtained.