The escalating global demand for polysaccharides as gelling agents and thickeners, particularly within the food industry, has intensified seaweed cultivation. While a portion of the residual biomass post-polysaccharide extraction is repurposed as animal feed or fertilizer, the majority is discarded as industrial waste. Due to the low lignin content of seaweed compared to woody biomass, it presents a promising feedstock for the efficient recovery of high-purity cellulose. This study investigates the feasibility of utilizing cellulose nanofibers (CNFs), derived from seaweed residue, as particulate stabilizers for the formulation of oil-in-water (O/W) Pickering emulsions.

The red macroalga Kappaphycus alvarezii, cultivated in Indonesia, served as the raw material. Following carrageenan extraction via hot alkaline aqueous treatment, the residual biomass was subjected to drying, mechanical pulverization, oxidative decolorization using hydrogen peroxide, and acid hydrolysis with sulfuric acid. The resulting CNFs were isolated through successive centrifugation and washing steps to achieve neutral pH.

Emulsification was conducted by dispersing CNFs in deionized water, followed by the addition of soybean oil. The mixture underwent high-speed rotor-stator homogenization to form a coarse emulsion, which was subsequently refined using high-pressure homogenization. Optical microscopy and laser diffraction analysis revealed a monomodal droplet size distribution centered around 15 µm, indicating the formation of a relatively uniform emulsion.

Stability assessments over a 7-day period at ambient temperature demonstrated that approximately 90% of oil droplets remained within the 5 - 20 µm range, with minimal coalescence observed. Even after 50 days of static storage, the droplet size distribution remained largely unchanged. This stability could be explained by the formation of Pickering emulsions, wherein CNFs adsorb onto the oil-water interface, thereby inhibiting Ostwald ripening.

In conclusion, the findings substantiate the potential of seaweed-derived CNFs as sustainable, bio-based stabilizers for the preparation of stable O/W emulsions, offering a viable alternative to conventional synthetic emulsifiers in food and related applications.

Acknowledgements: This research was supported by SATREPS, Japan Science and Technology Agency (JST, JPMJSA2307) / Japan International Cooperation Agency (JICA).