Extraction of Carotenoids from Bee Pollen Using Sunflower Oil: Evaluation of Time and Matrix-solvent Ratio

Abstract

Bee pollen has been recently highlighted as a potential source of fat-soluble bioactive compounds, in particular carotenoids. However, these compounds are trapped or linked to other components in both the inner pollen grain structure and the exine, which might hinder their bioavailability. The solvent-extraction of carotenoids from plant matrixes using edible oils has been profusely investigated, but there are no previous references to the use of bee pollen. In this work, the extraction kinetics of carotenoids from bee pollen was studied, using sunflower oil as an edible solvent, at different matrix-solvent ratios, in order to obtain carotenoid-rich oily extracts. Firstly, extractions were made by continuous stirring pollen and oil at room temperature, at ratios between 5 and 60 %wt during 24 h. Total carotenoids in the resulting extracts varied as a function of pollen ratio from 40.5 ± 1.7 mg ß-carotene/kg oil (5 %wt) to 968.8 ± 4.2 mg ß-carotene/kg oil (60 %wt). Subsequently, extractions were followed during 16 days at the three ratios that allowed for higher content of carotenoids (40%, 50%, and 60%wt). Concentration of carotenoids in the extracts increased significantly along the extraction time until day 12, following a second-order kinetic trend (R2>0.999). The content of carotenoids in the extracts at day 12 was significantly higher for higher matrix-solvent ratios, being 471.7 ± 10.1, 691.4 ± 17.7 and 1010.8 ± 11.6 mg ß-carotene/kg oil, for ratios 40 %wt, 50 %wt and 60 %wt, respectively. These findings indicate that, for a better extract quality, it is necessary to use 60%wt, or higher ratios, of bee pollen. Also, at room temperature, 12 days of extraction are required to guaranteeing the maximum extraction yield, regardless the matrix-pollen ratio. This work evidences the industrial feasibility of using bee pollen as a raw material for obtaining carotenoid-rich extracts, with potential as natural food colorants and bioactive ingredients, as suggested by previous reports. Furthermore, it is a rationale for future studies on the use of assisted-extraction techniques, such as microwaves and ultrasounds, for this purpose. Key-words: bee pollen, carotenoids, green extraction, sunflowe