Influence of Microwave hydrodiffusion and gravity (MHG) drying process on Ulva sp: Ulvan, molecular weight, rheology, and film development

Ulva sp green seaweed was dehydrated using the proposed Microwave hydrodiffusion and gravity (MHG) approach and the traditional convective air oven drying method (CO). The impact of MHG at the tested irradiation powers (50−250 W) was evaluated on the drying kinetics, energy requirements, microstructural aspects, proximate chemical composition, and colour features of the dried algal material. Furthermore, its influence was ascertained on the extractability, molecular weight, and structural and rheological characteristics of ulvan. The polymer obtained after drying under the selected MHG conditions was used to generate ulvan biobased film. Findings revealed that high irradiation powers required lower pre-treatment time: MHG at 200, 250 W-15 min, 100 W-45 min, 150 W-25 min, 50 W-240 min with moisture content around 10 g/100 g. MHG has no detrimental influence on colour and preserves the nutritional quality of the dried Ulva sp. Samples pre-treated at 150 W for 25 min displayed the highest ulvan yield (26.8 g/100 g). MHG does not affect the rheological and structural properties of ulvan and allows the recovery of high molecular ulvan weight, comparable to the commercial ones. The formed film produced from ulvan demonstrated strong mechanical behaviours that could be employed as a prospective biodegradable material. • Ulva sp seaweed was adequately dehydrated by Microwave hydrodiffusion and gravity (MHG). • MHG did not impact the colour and preserved the nutritional quality of the dried Ulva sp • MHG treatment (150 W, 25 min) involved the highest ulvan yield (26.8 %). • MHG did not not affect the rheological and structural properties of the ulvan. • Ulvan films showed strong mechanical features with potential for biodegradable material.