Application of high-pressure homogenization to improve physicochemical and antioxidant properties of almond hulls

Almond hull contains a high level of dietary fiber and antioxidants, yet is under-utilized, primarily as livestock feed. The present work aimed to evaluate the physiochemical and functional properties of almond hull powders, processed by high-pressure homogenization (HPH), and any changes to their antioxidant properties after HPH treatment. It was found that the HPH treatment reduced the mean particle size and created a porous structure of the almond hull powders after lyophilization (freeze drying); hence, a significant increase (p < 0.05) in water holding capacity and oil holding capacity after processing, resulted in a much-improved emulsifying capability. Additionally, based on their physical properties, the chosen variety (Carmel/Monterey) of almond hull extracts produced using the HPH process, showed the highest (1,1-diphenyl-2-picrylhydrazyl [DPPH]) radical-scavenging capacity (119.11 ± 5.27 mg TE/g dw) and ferric reducing power (167.52 ± 10.55 mg TE/g dw, under 22,000 psi = 152 MPa), along with the highest total flavonoid content (as 107.36 ± 3.76 mg QE/g dw). Overall, the high-pressure homogenization process has effectively improved the physicochemical and functional properties of almond hull powder. Practical Applications: This green technology can effectively improve the water holding capacity, oil capacity, emulsifying capacity, as well as a potential process that can enhance the bioavailability and functionality of almond hull, and therefore this abundantly available byproduct can be converted to various value-added ingredients and products such as emulsifier, clouding agent, nutritional supplement, and so on, in the huge interests of high-quality, all-natural, and healthy food market to date.