Abstract
The effect of initial moisture content on expansion ratio of the popped amaranth seeds in hot air and superheated steam at 170°C-320°C was investigated. For popping the seeds, a fluidized bed specifically designed for this study was used. Amaranth seeds samples were stored at 15°C and 25°C in sealed containers containing various saturated salt solutions for about 2 weeks in order to regulate the dry-basis moisture content which ranged from 0.03kg/kg to 0.38kg/kg. Breaking strength of raw amaranth seeds, one of the most important factors in popping, was measured with a rheometer. According to the results, it was found that the higher the initial moisture content of the raw seeds, the weaker the breaking strength. The maximum volume of the samples after popping was 8.7 times higher than raw samples' volume, provided that the initial moisture content of the raw samples was 0.15kg/kg, using hot air at 260°C for 15 seconds. Compared with hot air, the expansion ratio of the samples heated with superheated steam was 5-10% lower because the seed coats were softened by initial steam condensation. The relationship between the expansion ratio and the type of heating media, gas temperature, initial moisture content of popped amaranth seeds and heating time were clarified.
