Improved Sample Preparation and Optimized Solvent Extraction for Quantitation of Carotenoids

Accurate, rapid quantitation of key antioxidants such as carotenoids is important for assessment of food quality. Carotenoids are lipid-soluble pigments that are susceptible to oxidation due to their highly conjugated carbon-carbon double bonds. Therefore, the present work focuses on improving sample preparation to facilitate rapid analysis of carotenoids. The method involves optimized carotenoid extraction followed by direct HPLC analysis without further concentration and redissolution. For extraction, we tested the effect of blending time (1, 3 and 5 min) and 12 different solvent combinations for carotenoid extraction from cantaloupe (Cucumis melo var. cantalupensis) and oranges (Citrus sinensis), two popular fruits that are high in carotenoids. The identification of carotenoids was performed by LC-APCI-QTOF-HR-MS in positive-ionization mode. In melon, 1 min blending time gave significantly higher β-carotene content with CHCl₃: Ace (1:1) solvent. The optimized method was validated with tomato, watermelon, oranges, grapefruit, melon varieties and commercial products such as fruit juices. Among the different melon varieties, Western Shipper had significantly higher β-carotene (25.1 ± 0.4 µg/g) contents. In oranges, β-carotene and (all-E)-lycopene contents were 4.4 ± 0.1and 3.8 ± 0.1 µg/g, respectively. The optimized method has fewer unit operations and is reproducible for the quantitation of carotenoids and their isomers. This is the first report on the identification of ζ-carotene isomers, and lycopene isomers from cantaloupe varieties and lycopene from oranges. Graphical Abstract.