Effect of hammer and pin milling on triboelectrostatic separation of legume flour

The effect of hammer milling on the efficiency of a triboelectrostatic separation process to produce protein-, starch-, and seed-coat fibrous- enriched fractions from navy bean flour was investigated and the results were compared with previously published data for pin milled flour. Results revealed that samples collected from the middle and top part of the plate had significantly higher protein content and therefore lower starch content than the samples collected from the bottom of the plate. The bin that was located on the bottom of the separator, directly below the entrance of the ejector nozzle, contained higher amounts of seed-coat fibrous particles. A maximum protein content of 39.3 ± 0.7% and 32.6 ± 0.1% occurred on the middle/top and bottom part of the plate for optimum operating conditions. Hammer milling yielded a larger average particle size and a lower triboelectric separation efficiency compared to pin milling.