3.1 Particle Size Distribution
As shown in Fig. 1, the particle size distribution curves of the three commercially available walnut butter were similar (Fig. 1A). However, from Fig. 1 B it was observed that SS3 had the smallest D (4,3) value (33.55 ± 0.41 μm), which was significantly different from SS1 (50.76μm) and SS2 (55.14μm) (P<0.05). The fluidity of walnut butter increased with the reduction of particle size, which may result in a finer texture when consumed (Nam et al., 2014). Compared to commercial walnut butter, the FLWB prepared with MCT, DG, or CLA and defatted walnut meal showed a single-peak particle size distribution with a central peak width range of 1.78 – 796.21 μm for all samples (Fig. 1A). It was noticed that adding 65% of CLA or 70% CLA significantly moved the prominent peak of the particle size distribution to the left. It was found that the average particle size of DG walnut butter and GLA walnut butter decreased with increasing oil addition ratio. However, the average particle size of MCT walnut butter showed no significant difference at different MCT addition ratios. As the addition of DG or CLA increased from 60% to 70%, the average particle size of walnut butter decreased by 36.23% and 20.88%, respectively (Fig. 1B). The particle size of commercial walnut butter varied considerably as shown in D (4,3) for SS1, SS2, and SS3. The particle size of MCT-WB did not vary with the addition of MCT, but the particle size of DG-WB or CLA-WB could be adjusted by adjusting the addition of DG or CLA, which was used to prepare a product with a particle size more similar to that of commercial walnut butter. The above results indicated that the particle size data of FLWB could have similar characters with commercially walnut butter after ball milling treatments.