Vegetables carotenoid analysis, sample

Alkaline hydrolysis (saponification) has been used to remove contaminating lipids from fat-rich samples (e.g., pahn oil) and hydrolyze chlorophyll (e.g., green vegetables) and carotenoid esters (e.g., fruits). Xanthophylls, both free and with different degrees of esterification with a mixture of different fatty acids, are typically found in fruits, and saponification allows easier chromatographic separation, identification, and quantification. For this reason, most methods for quantitative carotenoid analysis include a saponification step. 

Eor more comprehensive information, Rodriguez-Bemaldo and Costa [440] have recently made an exhaustive review about carotenoid analysis in vegetable samples. Carotenoids can easily isomer-ize and be oxidized, leading to artifacts in the analysis. Therefore, the extraction must be carried out quickly, avoiding exposure to light, oxygen, and high temperatures. 

Rodriguez-Bemaldo de Quiros, A. Costa, H.S. 2006. Analysis of carotenoids in vegetable and plasma samples A review. J. Food Comp. Anal. 19 97-111. 

The detection and quantification of tocopherols, carotenoids, and chlorophylls in vegetable oil were effectively used for authentication pnrposes. The presence of tocopherols, carotenoids, and chlorophylls influence the oxidative stability of vegetable oils and their potential health benefits. Puspitasari-Nienaber et demonstrated the application of a rapid and reliable analysis method of direct injection of C-30 RP-NPLC with electrochemical detection for the simultaneous analysis of the above mentioned substances. Aliquots of vegetable oils were dissolved in appropriate solvents and injected directly without saponification, thus preventing sample loss or component degradation. Thus the effective separation of tocopherols, carotenoids, and chlorophylls was achieved. 

To avoid quantification errors caused by the multiple manipulations of the sample during the various steps of extraction and preparation, the use of an internal standard (IS) in combination with the external calibration is advisable. The IS must be chosen carefully, as it has to meet a series of minimum requirements. It must be a carotenoid pigment not present in the sample to be analyzed, it must be chromato-graphically separable from the others under the analytical conditions used, it must have a A ax absorption as close as possible to the A of detection employed, and it must be as stable as possible. Various ISs have been proposed (3-apo-8 -carotenal and canthaxanthin are commonly used in the analysis of vegetable foods.The use of artificial colorants, such as Congo red and Sudan 1, and of synthetic carotenoids not present in natural samples, such as C45-(3-carotene, has also been proposed. ... 

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