Inactivation of microorganisms on granular materials: Reduction of Bacillus amyloliquefaciens endospores on wheat grains in a low pressure plasma circulating fluidized bed reactor

Cereal grains can contain high bacterial loads so that a microbial reduction step is desired. Therefore, a low pressure circulating fluidized bed reactor for the treatment of granular materials was constructed, and an argon/oxygen plasma was ignited in the riser tube by an inductively coupled RF-source. With this setup, the viability of Bacillus amyloliquefaciens endospores, artificially deposited on wheat grains, could be reduced by over two logarithmic units within 30 s of effective treatment time. In addition, the influence of plasma power input and variation in oxygen gas admixture was studied. Based on energy influx measurements and the solution of the heat equation, a thermal inactivation effect and the thermal degradation of wheat grains could be excluded. No negative effects of plasma treatment on wheat grain properties were detected in flour and dough analyses.