The Effect of Superheated Steam Temperature, Velocity and Processing Time on Selected Oat Groat Post-Processing Properties

Abstract

The effect of superheated steam (SS) processing on selected oat groat post-processing properties was investigated. Raw and tempered oat groats were used for experiments in which the SS velocity (0.35-1.00 m/s), temperature (110-160oC) and processing time (1-30 min) were varied. The effect of a combination of two velocities (0.35 and 1.00 m/s) of SS processing on groats properties was also examined. The SS processed groats were compared to traditionally (kiln) processed groats. The considered post- processing properties of oat groats were: pasting properties (based on cold paste 64 test), moisture content, colour, peroxidase inactivation, and sensory characteristics. Generally, final viscosity of samples processed with SS was higher than the viscosity of groats processed in a kiln. Pasting properties of oat groats tempered before SS processing did not improve when compared to raw groats processed with SS. High velocity of SS (1.00 m/s), significantly (P<0.05) increased viscosity of processed product when compared to processing at low SS velocity (0.35 m/s). Use of high temperatures (140 - 160°C) in SS processing caused very low final moisture contents (4 to 7% wb) of groats and poor sensory characteristics two weeks after the processing. All tested SS temperature-time-velocity combinations proved to be effective in peroxidase inactivation. A selection of the SS processing parameters that produce oat groats with unique viscosities and acceptable sensory properties was made. The selected SS processing parameters were: temperature of 110°C, velocity of 1.00 m/s, and two processing times of 10 and 14 min, both of which gave acceptable products when compared to the traditionally processed product.