Ultrafine grinding improves the nutritional, physicochemical, and antioxidant activities of two varieties of whole-grain highland barley.

ABSTRACT

Effects of ultrafine grinding on the nutritional profile, physicochemical properties, and antioxidant activities of whole-grain highland barley (HB) including white highland barley (WHB) and black highland barley (BHB) were studied. Whole-grain HB was regularly ground and sieved through 80 mesh get 80 M powder, and HB was ultrafine grounded and sieved through 80 mesh, 150 mesh, and 200 mesh get 80UMM, 150UMM, and 200UMM samples. Particle size of WHB and BHB reduced significantly after ultrafine grinding. As the particle size decreased, moisture content of WHB and BHB decreased significantly, whereas fat content increased significantly. Redistribution of fiber components in WHB and BHB from insoluble to soluble fractions was also observed. Wherein, content of soluble pentosan of WHB and BHB increased significantly from 0.56% and 0.78% (80 M) to 0.91% and 1.14% (200UMM), respectively. Damaged starch of WHB and BHB increased significantly from 8.16% and 8.21% (80 M) to 10.29% and 10.07% (200UMM), respectively. Content of phenolic acid and flavonoid of WHB and BHB and associated antioxidant capacity were increased after ultrafine grinding. Color of L* value increased significantly, a* and b* values decreased significantly, indicating the whiteness of WHB and BHB was increased after ultrafine grinding. Pasting temperature of WHB and BHB decreased, whereas peak viscosity increased. X-ray diffraction patterns of HB showed typical A- and V-style polymorphs and the relative crystallinity of HB decreased as the particle size decreased. Taken together, ultrafine grinding has shown great potential in improving the nutritional, physiochemical, and antioxidant properties of whole-grain HB. Our research findings could help better understand the ultrafine grinded whole grain HB in food industry.