2. 3 Measurement of particle size
Particle size measurement are performed according to the previous method (Liu et al., 2007). The walnut butter was dissolved in sodium dodecyl sulfate (SDS) solution (0.1%) at a ratio of 1:50 (w/v), then stirred with a magnetic stirrer and shook with a vortex shaker until the walnut butter was well dispersed. The particle size of the samples was measured using a particle size analyzer (Mastersizer 2000, Malvern, UK). The walnut butter to be measured was added to 1000 mL of deionized water and the stirring paddle speed was set to 2000 rpm. The degree of shading was kept in the range of 10 - 15%. The refractive index of the dispersed phase (aqueous phase) was 1.330. The refractive index of the oil phases is shown in Table S1. The volumetric mean particle size D (4, 3) was used to indicate the sample particle size. The measurements were repeated at least three times for each sample.