Harmful Microorganisms Cross Contamination And Its Control Technologies In Feed Processing

This research aims to achieve the data of microbial residues and cross contamination which obtained from a representative formula feed factory, and to establish theoretical support for effective measures of controlling microbial residues and cross contamination. The research selected relative formula feed factories for experiment, therefore measured and investigated the microbial residues and cross contamination in raw material transport section, batching and mixing section, conditioning and pelleting section. The project also researched the control measure to reduce microbial residues. The research results are as follows.(1) The head of scraper, the base of the bucket elevator and the chute were regarded as sampling points. The total number of bacteria colonies, molds and coliform groups were treated as test index. Therefore, the feed from the raw material transport section was sampled and tested. The experiment indicated that, without cleaning the production line before production operation the earlier residues on sampling points would contaminate the first batch of raw materials with microbes. After delivering the contaminated materials, the residues in facilities would contaminate the following cleaner batches with microbes. The cross contamination of bacterium is more severe than that of molds and coliform groups. The severity of microbial residues and cross contamination would reduce as the batches of contaminated materials accumulates and quantities enlarges. Among the three critical sampling points the contamination in the chutes was the severest, and the bucket the lowest.(2) The bottom of mixer, the head of scraper, the base of the bucket elevator and the chute were treated as sampling points. The total numbers of bacterium, molds and coliform groups were regarded as experiment index. The feed from proportioning and mixing section are sampled and tested. The experiment indicated the following result. The residues of high-risk feed products would generate microbial cross contamination among the lower-risk feed products. The severity of such contamination would reduce as the quantity and batches of the following low-risk productions increase. Among the four critical sampling points, the level of microbial contamination was the highest in the chute and lowest in the bucket elevator.(3) the chute before the conditioner, the conditioner, the pellet mill, the cooler unit were regarded as sampling points. The total number of bacteria colonies, molds and coliform groups were treated as test index. The feed from conditioning and pelleting section are sampled and tested. The experiment indicated the following results. Conditioning and pelleting could effectively eliminate the microbes in the feed products. High-risk products generated microbial cross contamination among the following batches, and the location was the chute and the conditioner. The cross contamination of bacterium and coliform groups is severer than that of molds. Condition pelleting can reduce the microbial contamination in the feed products and in the meanwhile decrease the level of microbial cross contamination.(4) the bottom of mixer, the head of scraper, the base of bucket elevator and the chute were regarded as sampling points. The project utilized soybean meal as the flushing material, therefore sampled and tested in the production line. The experiment indicates the following result. The flushing technology may effectively reduce the microbial residues in the production facilities, hence reduce the risk of cross contamination. Within the load range of mixing machine, the more quantity of flushing material is employed, the better effect it manifests. However, the washing process can not reduce some stubborn remains inside the facilities.(5) The contamination level of the residual feed from the cooler and the bottom of bucket elevator is significantly lower than that of other key points, feed from the two key points has a lower risk of of microbial cross-contamination than that of other key points. The microbial contamination level of residual feed from the key points of the raw material transport section is overall higher than conditioning and pelleting section the risk of microbial cross-contamination of raw materials in the production line is greater than formula feed.