The Research Of Irradiation Microbiological Effects And Detection Technique On Coliform Bacteria In Spices

It is largely reported that coliform bacteria is quite sensitive to irradiation. But the amount of coliform bacteria in irradiated products after 4-9 kGy or higher dose irradiation still could not meet the requirement in the national hygienic standards, which is the reason to cause the dispute between the Irradiation Company and consumers. This research investigated the irradiation effects on coliform bacteria under different irradiation and culture condition, detected 338 irradiated spices samples, and analyzed the reasons for rejection of 16 irradiated spices due to the coliform bacteria content. The results were described as follows:1. In the research of the irradiation sensitivity of coliform bacteria under different media, bacteria content, species and irradiation dose rate ,we discovered that: the irradiation sensitivity of coliform bacteria in spices is between the sensitivity in Saline solution and Nutrient Broth. The coliform bacteria content of spices before irradiation has no significant change on the sensitivity. The four genera of coliform bacteria are all sensitive to irradiation, and the Dio-values are in the range of 0.05-0.18 kGy. The irradiation dose rate has no significant effect on the sensitivity of coliform bacteria. For practical application, the irradiation, which could meet the requirement of total amount bacteria of national standard, could be more than enough to control the coliform bacteria in spices.2. It is not found the resistant coliform bacteria in 338 irradiated spices samples during June 2000 to March 2002 Compared with the curve of irradiation effect and dose on Deinococcus radiodurans, it is indicated that coliform bacteria is not a irradiation resistant bacteria. The cytological characters such as the repair ability and the molecule weight of DNA could be the reasons of the irradiation sensitivity.3. The problems on the coliform bacteria detection method of the consumer should be the major reason for the rejection of irradiated spices. The problems could include the contamination during sampling, not strictly complying with the national standardsduring detection.4. Measuring the Dio.values of the coliform bacteria in irradiated spices couldensure the source of coliform bacteria. If the minimum irradiation dose is higher than8 DIG, the overload of coliform bacteria must be caused by contamination afterirradiation.