Abstract: Based on the principle of TTC-dehydrogenase reductive reaction, a procedure for the determination of dehydrogenase activity was established in four typical moulds such as Aspergillus flavus sp., A. candidus sp., A. glaucus sp. and Penicillium sp. that are widely distributed in stored cereal grains. The results revealed that the dehydrogenase had stable reaction in Tris-HCl buffer with optimal TTC concentration of 0.2 g/100 mL and acetone volume of 80%. The optimal determination temperature for four moulds was 30 ℃ and the optimal pH for Aspergillus flavus sp. and A. candidus sp. was 11.0, while the optimal pH for A. glaucus sp. and Penicillium sp. was 10 and 10.5, respectively. The reaction duration for Aspergillus flavus sp. and Penicillium sp. was 1.5 h, whereas the reaction duration for A. candidus sp. and A. glaucus sp. was 2.5 h. A high correlation was observed between dehydrogenase activity and mould number during wheat mildew process.

Key words: grain mould, dehydrogenase, TTC, cell activity