Amaranth seeds have a high nutritional value, and predisposition for popping when heated under proper conditions, accompanied by evaporation of contained water. Popping can be an effective and beneficial method for food processing. In this study, regulation and measurement of moisture content and its relationship to the mechanical properties of the amaranth seed were investigated. The effect of initial moisture content and gas temperature on expansion ratio, seed shape and browning, using hot air and superheated steam as heating media with a special fluidized bed for popping, was also studied. As a result, the maximum volume of the samples after popping was 8.7 times higher than the raw samples' volume, provided that the initial moisture content of the raw samples was 0.15 kg/kg, using hot air at 260 degrees C for 15 seconds. In the case of superheated steam, the optimum moisture content was slightly lower than that of hot air, and the expansion ratio was measurably lower because the seed coat was softened by initial steam condensation. The optimum condition for regulation of seed moisture content for popping was determined from the water sorption isotherm, with the optimum moisture content located just before the moisture content started to increase at a faster rate, with increasing relative humidity. The results of rheometer measurements showed that the degree of elasticity decreased and yield load was nearly constant when the moisture content was higher than the optimum value of 0.15.