Production and characterization of highly redispersible dried cellulose nanofibers exhibiting green color from leaves and stems of Centella asiatica

Abstract

Several studies have demonstrated potential of cellulose nanofibers (CNF) in various applications. However, no protocols are available for the production of spray-dried CNF with high water redispersibility; interfibrillar hydrogen bonding that occurs during spray drying is believed to be responsible for such lack of redispersibility. The present study therefore aimed to develop a protocol that can be used to prepare CNF powders from Centella asiatica via spray drying, with maltodextrin (MD) at CNF-to-MD ratios of 1:0, 1:1, 1:1.5, 1:2 and 1:2.5 as the drying aid. Chlorophylls within such plant were also complexed with zinc in order to allow the resulting redispersed CNF to exhibit thermally stable green color. The resulting powders were analyzed for their morphology, XRD pattern and FTIR spectra to confirm the interaction between CNF and MD. Appropriate CNF-to-MD ratios were determined based on the sedimentation behavior, morphology, fiber sizes and viscoelasticity of the redispersed suspensions. Only spray-dried powders with CNF-to-MD ratios of 1:2 and 1:2.5 showed no sedimentation during the entire storage period. Suspensions prepared from the powders produced at these ratios were also capable of regaining morphology and nanofibrous widths (19–20 nm) comparable to those of freshly prepared CNF suspension, with gel-like behavior and viscoelasticity remained unchanged. Zinc-chlorophylls complex possessed thermal stability under the employed spray drying condition, as confirmed by the retention of chlorophylls in the powders. Green color of redispersed CNF suspensions was similar to that of freshly prepared CNF suspension.