Red beetroot (Beta vulgaris) was cleaned, chopped and blended
with a high speed blender (FP-445, Otto, Thailand) at speed no. 4 for 5 min. A hydraulic press (B1, Central World Intertrade, Thailand) was used to squeeze the beetroot juice out from the minced beetroot until no liquid dripping from the pulp was observed (5 min). The juice was stored at 20 C and was thawed in a refrigerator prior to use.