Engineering miscellaneous particles from media-milled defatted walnut flour as novel food-grade Pickering stabilizers

Media milling, an efficient and organic solvent-free method without the use of chemical modification, has been developed to engineer novel walnut-based miscellaneous colloidal particles. The defatted walnut flour particles (DWFPs), which were prepared by a novel continuous phase transition extraction method operated under low temperature (i.e., 50-65 degrees C) followed by 6-h media milling, were spherical shape with an average size of 753.0 +/- 27.8 nm. These particles were mainly composed of proteins (55.6 +/- 0.2 wt%) and carbohydrates (24.0 +/- 0.2 wt %) and demonstrated the ability to form a gel-like network structure in Pickering emulsions (PEs). The visual observation and confocal laser scanning microscopy (CLSM) showed that the PE droplets stabilized by DWFPs had a good stability over a prolonged storage time (i.e., 3-month storage). Increasing particle concentration (c) in aqueous phase led to the increased emulsified phase volume, decreased oil droplet sizes, and increased storage moduli G' for the viscoelastic responses. As the oil volume fraction (phi) increased, the emulsified phase volume fraction and droplet size increased while their rheological properties shifted from fluid-like to gel-like behaviors. The method developed in this study is significant in value-added utilization of walnut products and provides a new insight into facile fabrication of stable food-grade Pickering emulsions-based functional foods using miscellaneous particle stabilizers from walnut extracts.