A clean label O/W pickering emulsion stabilized by pectin-containing lignocellulosic nanofibrils isolated from apple pomace

Abstract

With the increasing demand for clean-label food, LCNF is considered a promising candidate to replace artificial surfactants in O/W emulsion. However, the isolation of LCNF usually requires the use of costly and toxic oxidants or grafting reagents to introduce charged groups for higher fibrillation degree and better emulsifying properties. In this study, a new pectin-containing apple nanofibril (A-NF) with native dissociated carboxyl groups (-COO-) was successfully produced from apple pomace by alkaline demethylation followed by high-pressure homogenization. These “native” charged A-NFs are 10–30 nm in diameter and ∼1 μm in length, and can be well dispersed in water for several months due to the release of up to 1.30 mmol/g nanofibrils of -COO- from the insoluble pectin (ISP) fraction by alkaline demethylation. Among A-NFs, A–NF–24h showed the best emulsifying properties (70.85 m2/g of EAI and 94.71% of ESI) and highest emulsion stability (∼1.00 μm of the oil droplet size during 14-day storage). Emulsion microstructure showed that LCNF not only irreversibly adsorbed at the oil-water interface, providing electrostatic stability, but also offered depletion stability by fabricating an entangled network with the unabsorbed portion. Moreover, molecular dynamics simulations further explained that the A-NF system displayed lower absorption energy of −1659.43 kJ/mol and diffusion cofactor of oil molecules of 16.67 μm2/s than that of CNF system at the interface, thus enhancing the emulsion stability. Altogether, these native A-NFs exhibit good colloidal stability, comparable emulsifying properties and emulsion stability, and have promising applications in clean-label O/W emulsions.