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F - Characterization of Rice Grains

The aim of this Application Report is to introduce a QC-method that enables the prediction of processability of rice grains using the Anton Paar Powder Cell both by a mechanical test, as well as a fluidization test yielding the Cohesion Strength value or the pressure drop curve, respectively. Rice as an irregularly shaped particle of biological origin offers an interesting challenge for the study of its flow behavior. Along with the complex influence of surface texture different rice harvests will exhibit different surface chemistry which is influential in respect to the complex proteins that act glue like and will affect flow behavior. This complex interplay necessitates a direct measurement of its flow behavior instead of indirectly characterizing it using for instance grain size distribution and/or surface characterization methods. Lastly since fluidization is used as a processing step, e.g. to dry rice on an industrial scale, the fluidization measurements give an impression of other useful applications involving rice.


Two batches of crushed rice grains were analyzed. Depending on the batch flow problems are faced in processes. The grain size and size distribution of both samples is similar. The samples can neither be distinguished by visual inspection nor by haptic investigation. Therefore, a robust test methodology is needed, to be able to predict the processability of the batch. Both batches contained only a negligible amount of fines. In order to preserve the state of the samples and because of the general fragility of biological samples to temperature the rice was measured "as is" and not dried or sieved prior to measurement.

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