Abstract:To obtain submicron kelp powder with better physical properties and more concentrated particle size distribution, pretreatment was carried out with NaOH to shorten the time and wet grinding was used to reduce the particle size. The single-factor experiments and response surface method (RSM) were employed to optimize the technological conditions including the soaking liquid concentration, ratio of material to solvent and steeping time. The optimal conditions were set as NaOH mass fraction of 0.19%, soaking time of 11.00 min, and liquid-solid ratio of 20.00 mL·g-1. Under these conditions, the average particle size of kelp powder was 328.7 nm, D95 was 825.5 nm and the maximum particle size was 1106.2 nm, angle of repose was 62.5°, slip angle was 70.6°, water solubility was 20.1%, wetting time was 35.3 s, expansion force was 1 266%, and water-holding power was 3 197%. Compared with ultrafine kelp powder from market, the properties of nanoscale kelp powder were improved greatly with the angle of repose increased by 20.9°, slip angle increased by 27.9°, and water solubility increased by 50.0%. At the same time, the kelp powder physical properties were enhanced and improved which provides the basis for deep processing of kelp.