Physico-chemical properties of sunflower oil Pickering emulsions stabilized by cellulose nanocrystals-chitosan complex

Abstract

In this study we investigated the use of a polyelectrolyte complex formed by cellulose nanocrystals (CNC) and chitosan (Chit) as a stabilizing agent for Pickering emulsions. We demonstrated that chitosan reduces surface charge of CNC, resulting in polyelectrolyte complexes that efficiently stabilize emulsions. Emulsification processes reveal that a slight change in chitosan concentration can recharge surface of CNC. An optimal stabilizing complex containing 1% chitosan gives emulsions with minimal zeta potential, droplet size, creaming index values, along with high stability during storage, change in pH, and application of high centrifugal forces. The study also shows that the maximum neutralized surface charge of the CNC in the CNC-Chit complex allows for effective adsorption on the surface of sunflower oil droplets, producing a denser stabilizing layer with smaller droplet size. Also, chitosan addition is linked to improved stability and higher viscosity, with little dependence on ionic strength and temperature. Potentiometric titration allowed to reveal that five-time less chitosan is needed to neutralize surface charge of acetylated CNC compared to sulfated CNC. It is established that the CNC-Chit ratio eliminates background electrolyte ion participation in neutralizing surface charge, resulting in the absence of characteristic pKa values of the initial components. Wettability on a hydrophilic surface depends on the surface charge of the complex, enhancing wettability and adhesion performance with increased chitosan content. Also, we showed that tuning of stabilizer composition can change bioaccessability of lipophilic compounds during oral administration.