NDTnet 1998 Aug, Vol.3 No.8

Abstract

Frozen fish fingers and similar products are made from a mixture of different fish that arrive at the processing plant as frozen blocks. The frozen blocks are minced and the still frozen minced fish blocks are mixed and pressed into the desired shape, covered with batter and bread crumbs, baked on the outside (still with a frozen core), packed and stored in a deep freezer.

Products of the described type have very high quality requirements as the consumers are typically families with children or restaurants catering to same, where even the smallest bones are unacceptable. Previously, sample tests were conducted on selected blocks. The blocks were thawed and sieved. This was a very slow way of inspection where the production line had to wait for the raw material.

An X-ray based real-time inspection system has been designed to inspect incoming frozen fish blocks 100% and giving a completely accurate assessment of the quality of the blocks to enable the factory to calculate the correct purchase price as a function of the bone content. Real-time inspection ensures a minimum delay in passing incoming raw material to the production lines.

Due to the special high resolution imaging chain with a high conversion factor and a sensitive optical coupling to optimize contrast, it is possible to detect pin bones accurately (around 0.3 - 0.5 mm) while scanning at speeds of up to 100 mm/s in blocks around 60 mm thick.

A special design was required to meet the requirements of the food and health authorities. This includes the use of stainless steel for all metallic system parts such as frames for conveyors, motor covers, sensor covers and encapsulating the lead panels of the radiation shielded enclosure cabinet. In addition, all enclosures are required to meet IP 65 so the system can be hosed down with abrasive cleaning agents. As a special requirement, a fail safe system was designed to ensure that no specimen blocks could accidentially be subjected to X-ray doses in excess of the limits set by the food and drug authorities.

Implementation of the system has resulted in savings enabling payback of the full system in less than one year.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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