Table 3.

Foreign material removal/detection systems in food processing.

System	Removes/detects	Advantages	Disadvantages
Screens/sieves	Any material smaller than Screen/sieve	Simple, inexpensive	May suffer damage and contaminate product, difficult to clean and dry, difficult to filter suspensions, fat globules may plug the mesh
Magnets	Ferrous metal objects	Remove particles as small as dust	Only ferrous metals removed, must be consistently maintained
Optical/laser sorters	According to parameters set	Automated, High efficiency, Nondestructive	Expensive, needs additional equipment (compressed air, etc)
Metal detectors	Ferrous metals	Sense and remove ferrous, nonferrous, and stainless metals	Only detect electrically conductive or magnetic objects. Some foods create false positives.
X-ray	Metal, glass, rubber, stone, and some plastics	Nondestructive	High cost, uses high voltage, trouble detecting paper, wood chips, plastic, cartilage, and insects
Thermal imaging		Nondestructive, no radiation	Sensitive to temperature interference
NMR/MRI		Can determine other parameters than FM	Expensive, not very sensitive, low speed
Ultrasound	Wood splinters, glass, metal, and plastic	Nondestructive, cost effective	Only useful in homogeneous matrices
NIR	Coins, glass, rubber	Nonionizing, can penetrate air gaps	Must be calibrated
Hyperspatial imaging	Polymer, wood, metal	Uses complete spectrum of light	High cost, low speed, data storage and interpretation