I've inherited food safety system with a CCP at metal detector. According to Mettler Toledo instructions we need to check the detecor with a 2 mm iron standard. Someone decided to transfer this Toledo standard into CCP threshold, so justification was prepared to explain why this 2 mm body is the biggest we allow. There is written something like 'According to anatomy expertise, the narrowest part of oesophagus has diameter of 3 mm. Therefore the maximum foreign body diameter sould be 2 mm as maximum - this body will not harm a human and will be covered with biofilm and extract without ant difficulties'.
I asked the auther of this justification about the sources and he said he found this information in anatomy encyclopedia, but I can hardly find the same data in the web. Also I can hardly imagine my oesophageal 3 mm in demeter as maximum - I can swallow much bigger food pieces
So does anyone know what actually is the maximum diameter of even foreign body that an adult can intake without any harm? Maybe someone can share a link to a trustworthy anatomic encyclopedia
Your post is related to the justification of determining what size of foreign body contamination is considered a significant physical safety hazard.
This is a globally a much debated, and contentious, topic and there are many threads on this forum discussing the arguments. And chapters in published books.
The fact is that size is not the only criterion, eg hardness and sharpness also have biological importance. Plus the effect on the human body also.
The practical result from the POV of traditional haccp/ metal detectors is that most countries have Regulatory limits for metallic contamination as related to foods. And probably Russia also.
A useful summary of the biological nature of the problem from an American viewpoint is here –
Some references probably used for the above document are listed here –
In addition to the above article, one may also find a USFDA opinion that any metallic contamination in food constitutes adulteration so may be considered unacceptable from the latter’s POV.
From a practical metal detector POV, the situation regarding limits also relates to sensitivity. Many CCPs are practically based on the smallest size which is reliably capable of detection. This depends on the contaminant composition/shape, food matrix, instrument configuration/specification, etc. For Fe the minimum size detectable is often approx. 2mm diameter for a spherical ball in the least sensitive machine/food orientation. For stainless steel the limit must usually be increased. For example see the attachment in this thread -
I suggest you initially investigate the existence of local Regulatory limits.
PS - just for comparison, from memory, the limit for hazardous metallic contamination in some European countries, eg Holland, and Canada is maximum 2mm.