EFFECTS OF STORAGE AND PROCESSING ON THE ASCORBIC-ACID CONTENT OF CONCENTRATES PREPARED FROM CHAETOCEROS-CALCITRANS

Microalgae concentrates, prepared by centrifuging axenic (bacteria-free) cultures of Chaetoceros calcitrans (Paulsen) Takano, were processed and stored under different experimental conditions. The content of ascorbic acid was examined in the concentrates, to assess potential changes in their nutritional properties. In algae pastes stored at 4 degrees C, it reduced by 29% after 4 weeks storage. As most of the ascorbic acid was retained intracellularly (92%) after resuspension, most of the cells had remained intact. In frozen and dried paste preparations, the losses of ascorbic acid ranged from minor (11% after liquid nitrogen storage for 4 weeks) to major (greater than or equal to 94% after drying at 100 degrees C for 2 h or at 60 degrees C overnight). However, most of the remaining ascorbic acid (>85%) in these preparations was rapidly leached from cells upon resuspension. Therefore, pastes stored at 4 degrees C may have the best potential as an 'off-the-shelf' microalgal food product for mariculture. Pastes should now be assessed in animal feeding trials, before being recommended for widespread use in the industry.