Common control methods for foreign bodies in food include: manual selection, screen, metal detection, magnetic absorption and X-ray detection, etc.Different control methods have different application scope and effect, and each has its own advantages and disadvantages.The control of foreign matter in food needs to be based on prevention and integrated control with foreign matter detection to ensure food quality.
1. Appearance inspection
Direct visual inspection without any auxiliary tools, or direct visual inspection with auxiliary tools (e.g., light inspection table, magnifying glass, mirror), and indirect visual inspection (with camera system, e.g., control bottle inspection).The advantage of this inspection method is that the equipment investment is small, but the disadvantage is also obvious. The poor detection results are easy to lead to missed detection and low detection efficiency. The packaged products can not be detected, which is also the severe flaw of this detection method.
2. Screen detection
It is divided into vibrating screen (to separate different particle size or density of solid materials), screen mesh (to make the powder material through its own gravity through a sieve with a certain aperture) and pipe filtration (by the pressure generated by the pump to filter the liquid or powder to remove impurities).
This detection method of equipment investment is less, the application is relatively simple, but can only be used in liquid, powder products and small particle products, the same packaged products can not be used, and (metal) after the filter is damaged, easy to become the source of pollution of metal foreign bodies.
3. Magnetic separation
This is a test method used to separate metal foreign bodies from products.If the product under test is not magnetic, it will not be sucked away.Therefore, the magnetic separation system is not suitable for the separation of non-ferrous metals and organic materials.They can separate impurities of a wider range of shapes and sizes than metal detectors and X-ray equipment, but packaged products cannot be detected.
4. Metal detection
A technique for detecting metallic foreign bodies in food using magnetic and electrical conductivities of metals.When using a metal detector, the product passes through an electromagnetic field.In principle, metal detectors can detect all types of metal.However, magnetic metals (such as iron) are easier to detect than non-magnetic metals (non-ferrous metals and non-magnetic stainless steel).
The advantage is that magnetic and non-magnetic metals can be detected, detection accuracy is high, high efficiency, can control the metal foreign bodies in different production processes, processing links, bulk materials and packaging products can be detected online, and will not cause secondary pollution, but the equipment investment is high, the training requirements are also high.
5. X-rays
It refers to a detection technique that uses X-rays to distinguish between foreign bodies with different penetrating forces on materials of different densities.In addition to physical contaminants (such as metal fragments, glass fragments, and certain plastic and rubber compounds), it can also detect certain endogenous foreign bodies, such as bone, of greatest concern to the meat and aquatic industries.
X-ray foreign body detection has the advantage of real-time image intuitive and can detect metallic and some nonmetallic, can detect the aluminum film and rigid packaging products, cooperate with production line to achieve 100% online testing, and is not susceptible to electromagnetic interference, will not cause secondary pollution, good food foreign body detection of high water content, test data can be recorded and export, which can realize the product traceability, to the product will not affect the detection effect of packing sound, tie-in eyewinker automatic recognition software, can accomplish intelligent detection, eliminate defective products.
The above different food foreign body control technologies have their own advantages. Enterprises need to choose appropriate detection methods according to the characteristics of the products they produce. When necessary, these detection technologies can also be used comprehensively to promote their strengths and avoid weaknesses.