Tuna Inspection - Advances in Foreign Material Detection in
Process and Packaging and Assurance of Package Integrity
Four years ago at Infofish I introduced x-ray inspection of tuna. At that time the focus
was on the finished package. We reviewed the nature of x-ray from its discovery at the
beginning of the last century. What was known to many only as a matter of medical
investigation and more recently a means to improve airport and related security, x-ray is
increasingly becoming more and more common in the industrial setting. This is particularly the
case in the food industry.
X-ray Inspection expands the scope and application of contaminant inspection.
Not only does x-ray inspection extend contaminant detection beyond metal, but x-ray extends
the places where the inspection can be made.
In the tuna industry, as in all food operations, detailed procedures have been developed to
address the known sources of foreign materials into the process. The most common metal
elements have been hooks and knives and detection has been focused on metal detectors and
their use prior to packaging.
However, from my experience working with customers who use x-ray for all contaminants, they
have discovered other metal contaminants including:
 Shotgun pellets… used on sharks….an unintended consequence
 Flakes from unmaintained storage bins when used beyond their recommended life,
 Half an American dime coin, among others.
If metal detection is the primary concern, what can x-ray inspection add to improve the process?
•
•
•
•
X-ray Detects In the Finished Package
X-ray Expands Detectable Foreign Material
X-ray Detects Smaller Metal Pieces
X-ray Monitors the Complete Process
X-ray Detects in the Finished Package. In the absence of an imaging approach such as xray, it is impossible to determine the scope and the frequency of foreign material inclusion in
finished packaged tuna.
If you never look, you never see.
Detects More than Metal. If you only use metal detectors for foreign material inspection,
that is all that you will detect. Metal detectors only detect metal… and some of applications
where they are to inspect, for example frozen loin bags, they will be limited in terms of the size
of the contaminant that can be detected. X-ray expands the range of foreign material detected
to include bones, glass, stone, and many other materials including gasketing material and many
plastics.
X-ray Detects Metal Better than Metal Detectors. X-ray systems can be configured to detect
small metal contaminants by using smaller size diodes where the signal strength of the metal is
high relative to the product. For example, this 0.2 mm Diameter wire in this 3 Kg Pouch.
X-ray Systems Monitor the Process. The x-ray inspection provides a check on the processes
that may be employed upstream of the x-ray system. Thus, while addressing its clear
advantages in bone detection and quality control, the x-ray system confirms the effectiveness
and operational status of the metal detector systems, of similar people based systems, and can
spot the overlooked and the unplanned. X-ray images of every inspection can be exported to
“the cloud” for later review and confirmation of the quality of the inspection.
Social Media and the 24 Hour News Cycle
Underlying increased attention to food quality and avoidance of “bad news” is the intersection of
the modern news cycle and the importance of brand or reputation. This trend is definitely up.
Before you know of your problem, your employees are advising you of what the buzz is. The
ability of a story to be “trending” and be distributed far and wide grows with each “Tweet” from
Twitter or a “Like” status on Facebook or You Tube.
In the tuna industry, the value built up over years of applying good practices and building brand
and company loyalty abound. This is seen in these familiar marks.
Improvement in maintainability and other system designs enhance the longevity and the total
cost of ownership to the point where it is almost an immeasurable cost in the finished package.
For example, in a can line running 400 cans per minute over 5 years the cost is a mere
cipher…. Less than $0.0004 per can!
Your brands, trademarks, and company reputation represent the true value of your business.
Your customers often look at their brands in the same way.
They value their brand as much as anyone and will do whatever is necessary to protect this.
An Illustration of Can Inspection - Pinsa
An illustration of how one of the larger tuna processors in the Western Hemisphere uses x-ray
can illustrate some of the benefits from applying x-ray inspection.
Pinsa operates a modern tuna processing facility in Mazatlan. Like almost all tuna processors,
they have a brand image that has to be protected, in this case the Dolores brand.
Even when a processor does not market the product under its own brand, their customers have
sometimes an even more intense commitment to brand protection.
Introduction to the Process
To expand on their quality assurance and process monitoring program Pinsa installed their first
x-ray inspection system on their canning lines some four years ago. Although that effort
commences about the same time as Infofish in 2012, we had been having conversations about
x-ray for many years leading up to that first installation.
Pinsa competes for the local market with companies with equally recognizable and popular
brands. Some of these companies had already moved forward with x-ray inspection programs.
Every journey starts with a first step…. As one sees the benefits from the program started one is
encouraged to continue and expand. Pinsa has added systems over the past four years to
increase substantially the coverage of their production with x-ray inspection.
Location of the System. Like many tuna canners, Pinsa elected to inspect the can at the end
of the packaging line.
In this case after labeling. In their layout, cans are conveyed from the discharge of retorts
through the high speed labelers.
After labeling, the cans move through the section of the conveyor on which the ScanTrac Solo
x-ray inspection system is installed. In this process the speeds can range up to 1,000 cans per
minute.
The system inspects on the inspection conveyor so there is no disruption in the can flow from a
transfer from one conveyor to another. The ScanTrac takes an image of each can and
analyzes this for the presence of any x-ray detectable foreign material and ejects those
downstream of the system.
Like any inspection system, the ejection station is a critical part of the system. Cans must be
ejected positively from the line without disruption to the flow of the cans.
Here cans are accumulated in a manner so the cans can be easily associated with the image
that gave rise to the ejection. The last can ejected will be the can at the top of the stack.
In this case, the ejected can is taken from the accumulation chute and its x-ray image displayed.
The ejected can is taken as ejected to the laboratory for analysis. Confirmation of the detection
is made in the laboratory. Here the opened can is drained of liquid and probed for the material
that showed in the x-ray image.
In this case, a bone is found in the tuna. Experience with the x-ray images gives the user a
good sense of what is displayed on the x-ray image without the need to open the can and
confirm the process.
Working with an X-ray System.
As can be seen in the operation of this line….
The x-ray system does not require an operator. The Closed Cabinet system emits no radiation
outside the inspection assembly beyond that which occurs naturally…. Background radiation.
There are no restrictions on personnel movement, and no special badging is required for those
who work in the vicinity of the system. Maintenance consists of periodic review of coolant
levels. The working life of the x-ray tube improves each year and overall maintenance and
repairs can be scheduled on a monthly program.
Reject Detail Review. Toggling through the eject images shows how the x-ray system detects
dented cans as well as cans with irregular lid profiles. Dented cans are the most frequent
ejection cause. The system can be set-up so that small dents can be ignored or ejected at the
customer’s option.
This can be done by adjusting the sensitivity settings for detection as well as working with the
size of the contaminant makes analysis of each image using multiple inspection criteria such as
missing lid, underfilled containers, overfilled containers, and inverted cans as well as for
different types of foreign material.
Major defects that may have been able to still be labeled will be detected. Elimination of these
cans before multi-packing will minimize downstream jams that might otherwise occur. The
system can also detect inverted cans that will cause problems where stacked cans are sold in 3
and 4 can sleeved packs.
Diagnostic Program. Next to detection capability, the most important aspect of any inspection
system is its maintainability. Design considerations in an x-ray system go a long way towards
assuring maintainability. In the images already shown. The design of this x-ray system that
inspects from the side without container contact means that the motors, drives, and belts are not
part of the maintenance program since there are none. Equally important is how the system
helps the user trouble shoot when something does need maintenance.
Common practice now to meet the needs of tuna processors in plants that are often a long
distance from support offices in locales such as Samoa, Seychelles, Mauritius, as well as
Bangkok, General Santos City, or Guayaquil is to build in the technical tools to support the
system and then access them through the remote connectivity of the Internet.
Everyday sees advances in the extension of Internet connectivity throughout the world and at
speeds the make transfer of images such as x-ray systems generate a matter of standard
practice. Although we sometimes have to negotiate access with protective IT departments in
some companies, tuna processors are very receptive to the economics of remote support. The
cost is minimal and the support is immediate. For example at Peco InspX we maintain a 24
hour hot line that will get a technician connected to your system while you are on the call.
Once connected, the technician can review critical diagnostics in the system with the operations
and maintenance personnel as shown. From confirming repetitive timing signals to
irregularities in power, to escalating temperatures within the system.
In today’s x-ray systems, and indeed in many inspection systems, critical components are
enabled to provide continuous information on operating status and condition. These include
such systems applicable to tuna packaging such as fill level monitors and vacuum monitors.
These systems can be monitored and supported remotely to assure continuous performance or
support consistent with the needs of any CCP in your packaging program.
Big Data - Analytics. Over reaching each system and line monitoring operation is the arrival of
data analytics or “Big data.” With access to huge amounts of data generated by tuna packages
being inspected, seal integrity confirmed, volume assured, and a host of other data such as time
of day, speed, package supplier and more, these systems collect this data in real time and
provide immediate and trending analysis to assist the process.
A lot of this benefit comes in discovering just what is going on and what the variables are that
influence line performance. To give you an idea of the power available in the Internet, on the
Cloud, and in today’s computer based systems, x-ray systems running at over 1,000 cans or
bottles per minute can export a full image of every package inspected. Stored in the Cloud,
these images can be retrieved for subsequent analysis or to assist in understanding a particular
process with the benefit of total hindsight.
Bones in Fish. A direct fallout from x-ray inspection of finished packages such as cans and
pouches is the insight into the presence of bones. As shown in the video, bones make their
way into the finished package, notwithstanding continuous attention during the tuna processing.
Important to the x-ray operation is to monitor the frequency of these detections. Increased
detections can suggest a breakdown in the tuna preparation process. Without this data, the
frequency and any changes are completely unknown.
X-ray frequently shines a bright light on a condition that otherwise may have been
unmeasurable. We see this in application like beans and the occurrence of stones. The same
is true in tuna and the result is to look at means to detect bones before packaging.
This is where a lot of development is taking place. The key to any good x-ray detection
is a good picture. You know from blurry camera images you cannot distinguish what you are
looking at. You note the continuing emphasis on resolution with the pixel count on the cameras
in your mobile phone continuing to increase.
With x-ray, you need to start with a good camera. The most coherent and consistent xrays will be generated by the best x-ray tubes and x-ray tube configurations. At the same time,
the x-ray tube must also be sized with enough power to match the application. A 100 Watt
system will not yield a good image of a can running at 100 meters per minute, for example, and
a tube without a Beryllium window will lose resolution as contrasted to its Beryllium counterpart
when inspecting pouched tuna.
All x-ray systems are not the same… the configurations are made to match the package
as well as the requirements for the inspection. The inspection requirements will typically be
expressed in terms of the type of material to be detected, its size and shape, for the particular
package…. and, always an expression of both Type 1 and Type 2 errors… that is, the
occurrence of false rejects has got to be consistent with prudent business practice.
Keys to Inspection. In our pursuit of bone detection in loins and flaked tuna, here are some of
the rules we work with and the areas where improvements can be found.

Size. The contrast of a bad element to the good will always be more sensitive when the
amount of good product is minimized. X-ray works best looking across the smallest
dimension.




Uniformity (Product Noise). The more uniform the product, the easier to spot the
abnormality. Thus, to optimize a pouch inspection, by making this inspection after
putting the pouch through a roller will be a major improvement. Similarly in looking at
bone inspection prior to packaging, we need to review aspects of product handling and
conveyance to improve this critical part of the inspection process. This can be as simple
as sizing loin diameters prior to inspection.
X-ray Signal. As mentioned, where a broad range of x-ray signal is useful, a tube with a
Beryllium window will improve the resolution achieved. Metal ceramic tubes (as
contrasted with glass tubes) permit direct cooling through the walls of the tube in a
manner similar to automobile engines. This provides a more efficient means to increase
energy levels without the cooling baths associated with glass tubes.
Signal to Noise. The electronics, particularly in the receiver, can introduce measured
signal variation on account of their design, and this can be further influenced by the
manner in which the signal is shielded and collimated.
Diode Size. The smaller the diode, the resolution will improve, theoretically. This is
one variable and must be viewed in the context of the power you have in the system, the
type of tube and the objective you have for contaminant inspection. Is the attention on
metal or bone for example? I the standard system Peco InspX offers for pouch
inspection, the Allegro, we offer a selectable .8 mm diode or a .4 mm diode. To work
with the smaller diode (which is 25 % of the area of the 0.8 mm diode, the system must
adjust by running at a slower speed or with greater power…. There are trade-offs.
Developments. As we work to deliver tuna meat inspection systems we are considering a
range of system elements including multiple images, diode sizes system noise improvements,
and dynamic algorithms.
I had hoped to have more to share and tell on this point at this Infofish, but the project has
proved complex and competes with other applications of x-ray technology. I hope that by
Infofish 2018 we will be showing the results of our efforts and offering you an economical
alternative to ejecting cans with bones in them.