How to prevent cross-contamination in feed?
Due to the lagging construction of China's feed standard system, many operational technical specifications have not yet been established. For the testing of feed additives and illegal drugs, there is a lack of authoritative and versatile methods. Therefore, for most feed manufacturers in China, it is imperative to establish an effective feed safety guarantee measures and methods.
A drug added to a target feed for a certain purpose is present in a non-target feed for various reasons during processing, that is, cross-contamination. Feed cross-contamination exists in all feed mills, and reducing feed cross-contamination is an important measure to ensure feed safety. The author now analyzes the causes of drug cross-contamination from the perspective of feed processing, and proposes suggestions for improvement measures for feed manufacturers.
1 Analysis of the causes of pollution in feed processing
Drug contamination of feed can occur during feed processing, transport and storage. Among them, the pollution in the processing process mainly has the following aspects:
1.1 Vacuum system In the processing workshop of large and medium-sized feed mills, the vacuum system is distributed in all major aspects of the processing process, with the aim of reducing the dust generated in the processing process and purifying the production environment. For the collected dust, it is generally returned to the feed for economic reasons, but the delayed fall of the dust or the unreasonable design of the dust collection system may result in the drug additive being excessively absorbed.
1.2 Batching system Accurate ingredient is the premise and guarantee of strict implementation of production formula. Once the measurement of the pharmaceutical additive is mistaken and not found in time, the follow-up section is irreparable and will cause serious pollution.
1.3 Hybrid system mixing process is a process of evenly distributing various components, and is also the main link to produce drug contamination. The reason is that the mixing time setting is unreasonable, the expected mixing effect is not achieved, and the mixing unevenness or excessive mixing phenomenon occurs; the mixer is not properly designed, resulting in incomplete discharge, residual feed; the mixing machine mouth cannot be closed. Or the gasket is damaged due to damage; the feed has a high viscosity (due to the addition of molasses and grease) or due to static electricity attached to the inner wall of the mixer, the top end and the air return tube.
1.4 Buffer bin The buffer bin is a processing device that balances the processing capacity between devices to facilitate continuous production. However, if the buffer volume is too small, the design is unreasonable, or it is adhered due to static electricity or moisture, the residual feed cannot be completely removed, and drug contamination can also occur.
1.5 The conveying distance of the conveyor is too long, the design or operation of the horizontal conveying equipment is unreasonable, the bottom clearance is too large, and the feed may be caused by static electricity or moisture.
1.6 Bucket elevators Bucket elevators generally have very little drug residue, but static electricity, humidity and excessive viscosity can cause residue on the lifting bucket or base, causing pollution.
1.7 The drug contamination caused by the silo silo is mainly caused by unreasonable design or operation (slope is less than 60 degrees). In addition, the undulation inside the silo, incomplete removal of the silo, and the use of the same silo in both the medicated and non-medicated feeds can lead to contamination of the feed drug.
1.8 Production Sorting Production ordering is the order in which different types or different formulas are produced. Due to the operation technology, production technology, production equipment, etc., the feed products produced in the previous batch will have an impact on the products subsequently produced, so the incorrect production sequencing is also the cause of drug contamination.
2 How to reduce or prevent pollution in processing?
Contamination can be significantly reduced by simply modifying the production sequencing or adjusting the mechanical equipment. For some manufacturers, it may be necessary to repair and replace mechanical equipment, or even complete a complete production system. The measures to reduce drug pollution mainly include the following aspects:
2.1 Production process design When designing the feed processing technology, it is necessary to shorten the conveying distance as much as possible, use less horizontal conveying equipment, and adopt the form of distributor and self-flow conveying as much as possible. For horizontal conveying equipment, a scraper conveyor with automatic removal should be used whenever possible. Under the conditions that meet the process requirements, minimize the number of material upgrades and the number of transition hoppers. The suction and dust removal system should be equipped with an independent wind network as much as possible. The dosing of the composite premix is ​​arranged as far as possible in the upper part of the mixer.
2.2 The general principle of the order of feed production is to produce the feed without drug and then the feed containing the drug; the feed with the same drug or the feed for the same animal should be arranged together, and the feed with high drug content should be processed first. Reprocessing feeds with low drug content; the drug-containing feeds used in the same type of animals first produce feeds that are not restricted by the withdrawal period, such as sows during the lactation period (pre-stage), and then produce feeds that are restricted by the withdrawal period; When the sales volume of a medicated feed is much higher than that without medicated feed, consider setting up a completely separate dedicated production line to minimize the possibility of cross-contamination. Reasonable sorting should be reflected in the entire processing system, from the beginning of the warehouse to be crushed to the end of the finished warehouse.
2.3 Electrostatic adhesion In order to eliminate static electricity, ground wire can be installed on the equipment; non-electrostatic premixing agent is purchased; liquid raw material is added to control dust and static electricity is reduced; and an oscillator is installed at a place where the feed is easy to be attached to shake off the attached matter.
2.4 Dust collection system correctly design the air flow rate and flow pressure of the dust collecting wind net, and clean the dust in the whole system in time; use liquid raw materials to reduce dust; the dust collected during the process of producing drug-containing feed should be discarded or played back to the next Batched with similar drug-containing feeds.
2.5 Mixer For the drug-containing feed, a high uniformity mixer should be used, or the spacing of the stirring spiral belt, the stirring paddle and the bottom plate of the existing mixer should be adjusted. The easiest way is to install a plastic brush or air cleaning nozzle on the stirring spiral to remove residue. The correct order and timing of the feed is also critical, typically when the mixer is full of 1/2 to 3/4.
2.6 Bucket elevator adjusts the bucket elevator base to reduce the height of the hopper so that it can be cleaned more cleanly; install air cleaning nozzle; the inner surface and transition part must be clean and smooth.
2.7 The silo silo design should be scientific; when the type of feed stored changes, it should be inspected and cleaned; install the oscillator to remove the residue.
2.8 The residue of the conditioner, granulator and dryer to the dryer can be solved by paying attention and clearing it in time. The residue in the conditioner and granulator can be solved by “flushingâ€. “Flushing†uses a certain amount of certain raw materials, such as corn flour, soybean meal or wheat bran, to remove the residue of the drug-containing feed or animal-derived feed on the equipment. “Flushing†can also start from the warehouse to be pulverized throughout the production process. The used "flush" material can be stored with the appropriate label and reused when producing the appropriate feed.
Feed safety is a systematic project. In addition to pollution in feed processing, a sound quality management system and system is also an important aspect affecting feed safety. Feed processing enterprises should pay attention to it in many aspects.
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