Contamination And Variation Law Of Harmful Microorganisms In Typical Aquatic, Livestock And Poultry Feed Processing

The purpose of this paper is to obtain the harmful microbial level main feed ingredients in typical aqua-feed, animal feed factories, the variation law of harmful microorganisms in feed being processed in the production lines and the changes of harmful microorganisms in finished feed from the feed mills to feeding farms under different storage conditions, so as to provide a scientific basis for taking effective prevention measures. The main results were as follows:1)The main feed ingredients of feed mills were sampled and detected for the total number of bacteria mold, coliforms, staphylococcus aureus, salmonella, aspergillus flavus, fusarium yellow, ochratoxin and other pathogens. The results showed that: Native fish meal had the highest contamination level of total bacteria, 1.5×106 cfu/g; Fine bran had the most serious mold contamination,4.0×104 cfu/g;In the vegetable ingredients, brewer’s grains, brewer’s yeast, coarse and fine wheat bran, fermented soybean meal are the key ingredients for harmful microbial monitoring and control, for the animal feed ingredients, fish meal, blood meal, fish soluble are the focal point of harmful microbial prevention.2)The harmful microbial level of feed samples taken from before and after the main process steps in multi production lines were tested, the results showed that:In grinding and mixing stages, the temperature rises and water vapor increases in the ingredients by processing could easily lead to microbial development, the ground meal materials had 20% higher bacteria and mold counts than the materials before grinding and receiving; coliform group did not increase obviously; In conditioning and pelleting stages of the 5 production line, the mold and coliform counts of the feed samples including pig feed, broiler feed, duck feed, extruded feed and shrimp feed just after pelleting reduced 80% than that before pelleting, and the bacteria counts cut down 60%. Conditioning and pelleting have the extraordinary sterilizing effect; From cooling to packaging stage, bacteria counts of feed sample increased 30%, higher than mold and coliform, that indicates the re-contaminate risk in the process.3) The samples were taken from the point where residue and microbial contamination more likely to occur, include boot bottom of bucket elevator in the dumping stage, the inner of bag houses of dust collectors for grinding, super micro pulverizer, boot bottom of bucket elevator after super micro pulverizer, the chutes after the second proportioning, the chutes before pelleting bin, the boot bottom of bucket elevator in silo receiving, the tail part of the chain conveyors and the boot bottom of bucket elevators after main mixers, the harmful microbial levels were analyzed, the result showed that the Bacteria counts and mold counts were near or surpass 105 cfu/g, and surpass the maximum allowance of national feed sanitary standard. The harmful microbial contamination which is surpass 106 cfu/g in the chutes was serious,.4)Feed samples were taken from the packaging point, fished product warehouse of feed mills, feed store house in animal feeding farms, and tested for the harmful microbial, The result showed that, the harmful microbial content of the same batch feed product is highly correlative with the harmful microbial content in processing equipment, the correlation coefficients of mold and coliform are over 0.95; The harmful microbial content is closely related with store time and environment, therefore, the good package quality, correct storage method, the least store time will be good for assure the feed product to meet the quality requirement in shelf life.5) The feed samples with harmful microbial were sterilized by different dose irradiation, the results showed that after irradiation of 5.0 kGy, bacterial content of three samples were reduced to 1.7×104 cfu/g、5×103 cfu/g、0 cfu/g, the bacterial sterilization efficiency reached to 99.6%, 96.45%, 100%; Under the irradiation dose of 10.0 kGy, bacterial sterilization effect reached 100%. Irradiation sterilization is an effective way to reduce the harmful microbial content of finished feed products.