Abstract: Superfine grinding of dried apple slices was conducted for different times (1, 3, 5, 10, 20 and 30 min) after rough grinding. The effect of superfine grinding time on physicochemical properties and microstructure of apple powder was determined. For this purpose, the particle size and structure of apple powder were determined by laser particle size analyzer and scanning electron microscope. The results showed that after superfine grinding, the particle size of apple powder became smaller, and the size distribution became more uniform. Compared with rough grinding, the swelling capacity, water solubility, water-holding capacity and cation exchange capacity of superfine apple powder increased, and the bulk density decreased (P < 0.05). With the increase in superfine grinding time, the water-holding capacity increased gradually (P < 0.05), the bulk density and swelling capacity did not significantly change (P > 0.05), and the water solubility and cation exchange capacity first increased and then remained almost unchanged. This experiment may provide useful data for the utilization and deep processing of apple.

Key words: apple powder, superfine grinding, coarse grinding, particle size, physicochemical properties