Fabrication of cellulose nanofibers from waste brown algae and their potential application as milk thickeners

Abstract

Seafood wastes contain important bioactive polysaccharides that are good candidates for food additives. In this work, cellulose was isolated from the waste of brown algae (BA) after alginate extraction and was demonstrated to be cellulose I with a weight-average molecular weight (Mw) of 2.69 × 105. The results of scanning electron microscope (SEM) measurements indicated that BA cellulose existed as nanofibers in the BA. Subsequently, the BA cellulose was oxidized by NaClO to obtain well-dispersed cellulose nanofibers in water. The results of transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed that the average values of the width, length and aspect ratio of BA cellulose nanofibers were 4 nm, 1.1 μm, and 275, respectively. The rheology behavior of the nanofiber suspension in water demonstrated its high viscosity and shear-thinning behavior. More importantly, the BA cellulose nanofibers exhibited superior thickening behavior in milk because the BA cellulose nanofibers absorb casein micelles through hydrogen bonds to form a weak gel-like structure. The MTT test confirmed the nanofibers' safety and good biocompatibility. The cellulose nanofibers derived from an abundant marine bioresource could be expected to have applications in the food industry. This work opened a new pathway to fabricate bioactive cellulose nanofibers with a high aspect ratio as a food thickener.