Preliminary studies on decontamination of some dried herbal products by gamma irradiation

Abstract

Seven dried herbal products (DHP) were decontaminated using gamma radiation. The microbial loads (total viable count, TVC) of the raw and irradiated products were determined using the methods of serial dilutions and pour plate. Based on international standards for microbial load, the effective decontamination doses were determined for the DHP. The range of TVC for the DHP was 10 5 to 10 9 cfu/g. Milled roots of Cryptolepis sanguinolenta and milled stems and leaves of Desmodium adscendens had the highest counts of 8.0 × 10 8 and 2.0 × 10 9 cfu/g, respectively. Powdered seeds of Moringa olifera and Grifornia simplicifolia and the seeds of Voacanga africanus had relatively low TVCs of 6.4 × 10 5 , 6.6 × 10 6 and 1.3 × 10 6 cfu/g, respectively. Irradiation with medium doses of 2.5 to 7.5 kGy reduced microbial loads of the DHP by 3 to 6 log cycles. A dose of 10 kGy reduced the microbial load by 4 to7 log cycles and a dose of 15 kGy eliminated viable cells from all the DHP. Effective decontamination doses for the DHP were estimated to range from 2.5 to 10.0 kGy. Decontamination using gamma irradiation can improve the microbial quality and enhance the safety of DHP for both the domestic and export markets.