2. 4 Color of walnut butter
The determination of color was referenced to a previous method (Sun et al., 2015). The color parameters of walnut butter were determined with a colorimeter (Ultrascan VIS, HuntereLab, USA). Where L* reflected the brightness of the product, a* indicated a red-green value and b* indicated a yellow-blue value. The measurements were repeated at least three times for each sample.