INVESTIGATION OF FOAM-MAT DRYING CONDITIONS FOR Spirulina POWDER PRODUCTION

Abstract

This study aimed to develop a foam-mat drying process for producing high-quality Spirulina powder and to evaluate the effects of key processing parameters on the final product. The process consisted of two main stages: Foam formation from a fresh Spirulina slurry and foam-mat drying. The investigated factors included ultrasonic treatment time of the algae slurry (10, 20, 30, 40, 50 minutes), algae-to-solvent ratios (1: 10, 1: 15, 1: 20, 1: 25, 1: 30 w/v), concentrations of the foaming stabilizer carboxymethyl cellulose (CMC) at 0.25, 0.5, 0.75, 1%, whipping times of 1, 3, 5, 7, 9 minutes, foam layer thicknesses of 2, 3, 4, 5, 6 mm, and drying temperatures of 50, 60, 70, 80°C. Optimal foaming conditions were achieved at 30 minutes of ultrasonication, a Spirulina-to-water ratio of 1: 25 (w/v), 0.75% CMC (based on the biomass) and 3 minutes of whipping. In the drying stage, foam layers 3 - 4 mm thick dried at 70 °C required approximately 200 - 220 min and yielded powders with high solids recovery (~ 91%), good solubility, a protein content of about 66.6 g/100 g dry weight and a phycocyanin content of approximately 93.6 mg/g dry weight. Compared with vacuum drying at the same temperature, foam-mat drying markedly shortened the drying time and preserved phycocyanin to a significantly greater extent, while maintaining similar recovery yields. This highlights its potential as a suitable technology for producing Spirulina powders enriched in bioactive compounds. The foam‐mat drying process developed in this study satisfactorily met the research objectives. Optimization of whipping conditions and stabilizer ratios improved drying efficiency while preserving protein content and maintaining the final powder moisture below 5%. The results demonstrate that foam‐mat drying is a suitable method for processing Spirulina, enhancing drying rate, improving powder quality, and providing a foundation for future scale-up.