Carotene content of Azolla and its variations during drying and storage treatments

Abstract

The carotene content of six Azolla strains was analysed at four representative stages of their population growth curve under two culture conditions (greenhouse and growth chamber). On fresh material, the carotene content ranged from 206 to 619 mg kg −1 on a dry matter (DM) basis and differed significantly between strains. In both culture conditions, Azolla filiculoides 173FI was the best source of carotene and Azolla mexicana 220ME the poorest source. Carotene content was maximal during the linear phase of growth and minimal during the stationary phase for the six strains and the two culture conditions. The influences of drying and storage were also studied on one strain (173FI). The carotene content decreased during oven drying at 50°C at a constant rate of 6.0% h −1 for 32 h (after 8, 16 and 32 h the losses reached 45, 71 and 86%, respectively). A 4 months storage at room temperature after 17 h of drying at 60°C lowered carotene content by 69% at a constant rate of 1% per day (from 259 to 79 mg kg −1 DM). Results show that, in addition to being used as a source of plant proteins, Azolla has a clear potential as a source of provitamin A for animal feeding when used fresh; Azolla selection programmes, therefore, need to include carotene content as one criterion among others.