Sustainable Continuous Drying of High Moisture Content Seaweed via Twin Screw Extrusion—A Proof of Concept Study and Statistical Analysis

Seaweed gained a great deal of interest in recent years as a valuable source in food, cosmetics, and pharmaceuticals. Efficient economic utilization of seaweed depends on the techniques employed to remove their high moisture content (MC). This study proposes a novel continuous drying technique for Fucus vesiculosus seaweed biomass using twin-screw extrusion (TSE), comparing findings with hot air oven drying (OD). The effects of processing temperatures (35°C-85°C) and drying airflow rates (2.5-15 L/min) on final MC, total phenolic content (TPC), particle size distribution (PSD), and topography of TSE dried seaweed were investigated. For OD, batch drying was fixed at 35°C and 45°C in a (Binder drying and heating chamber ED115). Statistical analysis on obtained results was also performed using multiple linear regression (MLR) to see if input variables had a significant effect on the obtained results. Results showcased superior drying via TSE wherein the average drying time was approximately 12 min. At an airflow rate of 12.5 L/min and processing temperatures of 45°C, MC of seaweed was reduced from 70% to 13% whilst preserving TPC (8.17-7.26 g phloroglucinol equivalent (PGE)/100 g DW). In contrast, for similar processing times via OD, MC was reduced from 70% to 62.5%, with TPC decreasing to 6.25 g PGE/100 g DW. Statistical analysis revealed that both temperature and airflow rate significantly effected both MC and TPC for TSE dried samples. The data suggest that TSE is a promising unit operation for the continuous drying of F. vesiculosus in preparation for subsequent processing of seaweed products.