A Comprehensive Analytical Workflow for the Quantification of Carotenoid Presence in Chicken Egg Yolks

Chicken egg is included among the main components of the human diet as an important source of nutrients, such as proteins, lipids, vitamins, minerals and carotenoids. The latter are terpenoid pigments present in egg yolks, providing their color and playing a vital role because of their significant bioactivities. The carotenoid content of egg yolk varies considerably since it is strongly influenced by the respective laying hens’ farming and feeding procedures, and there is therefore a need to establish an efficient method for their assessment. The absence of such a method prompted us to develop a novel procedure consisting of the extraction, saponification and quantitative assessment of contained carotenoids. For this purpose, the optimal conditions for the extraction of carotenoids from egg yolks were defined, along with the optimal saponification conditions of carotenoids, with respect to reaction duration and pH influence on the extract’s contents of lutein and zeaxanthin. The carotenoid content of extracts was determined using a novel, developed herein LC-MS/MS method that allows the accurate, fast and simultaneous quantitation of the 11 most abundant carotenoids in egg yolks. The method accuracy and reliability were validated for six different parameters determined for each analyte. The novel procedure was applied for the assessment of the carotenoid content of ten egg yolks of diverse origin, indicating the bioactive carotenoids lutein and retinol as the most abundant, while lesser amounts of the remaining natural and synthetic carotenoids were found and there was no trace of fucoxanthin or astaxanthin molecules. The results herein revealed a variation in the carotenoid content of chicken eggs that depended on the diet and farming method of egg-laying hens.