Food X-Ray Inspection | X-Ray Foreign Object Detection | X-Ray Inspection Machine

Food manufacturers face continuous risks from physical contaminants during raw material handling, processing, weighing, filling and packaging. Metal fragments, glass, stones, bone fragments and certain dense plastic materials can enter the production process through raw materials, processing equipment or packaging.

Metal detectors remain an important inspection technology for metallic contaminants. However, when a production line also needs to identify certain non-metallic foreign objects, food X-ray inspection provides a broader inspection approach.

X-ray inspection systems generate images of the internal structure of products by measuring how X-rays are attenuated as they pass through the product. Depending on the product and inspection conditions, X-ray systems can identify contaminants such as metal, glass, stone, bone and certain dense plastics.

However, X-ray inspection should not be understood as a technology that can detect every foreign object under every condition. Actual detection performance depends on the contaminant, product density, product thickness, package structure, contaminant size and orientation, X-ray configuration, detector performance and image-processing settings.

For this reason, professional X-ray inspection should always be validated with the actual product and representative test samples.

What Is a Food X-Ray Inspection Machine?

A food X-ray inspection machine is a non-destructive inspection system used to examine products or packages for foreign objects and, depending on the system configuration, certain product or packaging defects.

A typical system contains several interconnected components:

• X-ray source
• Linear detector
• Conveyor system
• Industrial control and image-processing system
• Human-machine interface (HMI)
• Detection algorithms
• Product-specific shielding or inspection settings
• Alarm and automatic rejection system

The basic inspection process can be summarized as:

X-Ray Generation → Product Scanning → Detector Acquisition → Image Analysis → OK/NG Decision → Alarm or Rejection

The X-ray source generates the beam, while the detector receives the X-rays transmitted through the product.

The detector converts the received signal into image information. The image-processing system then analyzes the image and determines whether the product contains an abnormal region that may indicate a foreign object.

This means that X-ray inspection is not simply an X-ray generator. It is a complete combination of X-ray imaging, electronic control, image analysis and product handling.

How Does Food X-Ray Inspection Work?

The fundamental principle is based on the different attenuation of X-rays as they pass through different materials.

When an X-ray beam passes through a product, part of its energy is absorbed or scattered. The amount of attenuation depends on the material and the thickness that the X-ray beam travels through.

The detector measures the transmitted X-ray signal and converts it into an image.

In a conventional grayscale X-ray image, areas that attenuate more X-rays can appear darker than surrounding product areas. Image-processing algorithms then analyze these differences to identify potential contaminants.

The important point is that X-ray inspection does not simply identify an object because it is "dense."

What matters in practical food inspection is the difference in X-ray attenuation between the contaminant and the surrounding product, together with the contaminant's size, shape and position.

This is why the same contaminant can have different detection performance in different products.

What Can an X-Ray Food Inspection Machine Detect?

One of the main advantages of X-ray inspection is that it can identify certain non-metallic contaminants that conventional metal detectors cannot detect.

Typical applications include:

Metal

X-ray inspection can detect ferrous, non-ferrous and stainless-steel contaminants.

Glass

Glass fragments can be detected when their size, density and contrast provide sufficient separation from the surrounding product.

Stone

Stone and mineral contaminants are common targets for food X-ray inspection, particularly in agricultural and bulk-food applications.

Bone

Certain bone fragments, particularly calcified bone, can be detected when sufficient contrast exists between the bone and the surrounding food.

Ceramic

Ceramic materials can provide sufficient X-ray contrast for detection in suitable applications.

Dense Plastic

Certain higher-density plastics can be detected by X-ray inspection. However, low-density plastics can be much more difficult to detect.

Industry guidance shows that glass, rock, bone and some plastics can have different levels of X-ray detectability, while materials such as hair, wood and some low-density plastics may not be reliably detectable. Actual performance should therefore be confirmed through application testing.

An important limitation

A professional X-ray inspection specification should not simply state:

"The machine detects all foreign objects."

A more technically accurate approach is:

The system is designed to detect target foreign objects that provide sufficient X-ray contrast against the product under the specified inspection conditions.

This distinction is particularly important when dealing with very small, low-density or irregularly positioned contaminants.

X-Ray Inspection vs. Metal Detection

X-ray inspection and metal detection use different physical principles and can complement each other in a food safety program.

* Actual detection capability depends on product, contaminant properties, package structure, size, orientation and machine configuration.

Metal detectors are highly effective for metallic contamination. X-ray systems add the ability to inspect for certain non-metallic contaminants.

This makes X-ray particularly useful when a manufacturer needs to address a wider range of physical contamination risks, including metal, glass, stone, bone and certain dense plastics.

The choice between the two technologies should therefore be based on the product and contamination risk rather than on the assumption that one technology is always better.

What Affects X-Ray Detection Sensitivity?

There is no single detection sensitivity value that applies equally to every food product.

Several factors influence actual performance.

1. Product Density

The product itself creates the background image.

If the product has a relatively uniform structure, a foreign object may produce a clear contrast.

If the product contains large variations in density, the background can become more complex and make small contaminants more difficult to distinguish.

2. Product Thickness

The thicker the product that the X-ray beam must penetrate, the more material the X-rays pass through.

This can affect image contrast and therefore detection performance.

A contaminant that is easy to identify in a thin package may be more difficult to detect in a thicker or denser product.

3. Foreign Object Material

Different materials attenuate X-rays differently.

Metal generally produces strong attenuation, while glass, stone, bone and dense plastics can also provide detectable contrast under suitable conditions.

Low-density materials may provide much weaker contrast.

4. Foreign Object Size and Shape

Size is important, but shape also matters.

A thin wire, for example, may produce a different image depending on its length and orientation relative to the X-ray beam.

This is why a test specification should define not only the material and diameter of a test piece, but also the test conditions.

5. Package Structure

The packaging itself contributes to the X-ray image.

Flexible pouches, trays, cartons, cans and other packaging formats can produce different inspection conditions.

X-ray inspection is particularly useful for certain products packaged in metallized or foil-based materials, where conventional metal detection may be affected by the package itself.

6. X-Ray Source and Detector

X-ray source settings, detector characteristics and image quality all influence the available inspection signal.

Higher X-ray energy is not automatically equivalent to better detection for every product.

The source and detector should be selected and configured according to the product thickness, package structure and inspection objective.

7. Conveyor Speed

The product must pass through the inspection zone at a controlled speed.

The detector acquisition, image processing and reject system must operate consistently with the production line.

Therefore, practical inspection capacity should be evaluated using the complete production condition rather than conveyor speed alone.

X-Ray Image Analysis and Detection Algorithms

The X-ray detector creates the image, but image analysis determines how the system interprets that image.

Depending on the equipment design, image-processing systems may use different combinations of:

• Grayscale analysis
• Contrast analysis
• Shape analysis
• Edge or gradient analysis
• Background correction
• Product-specific masking
• Region-of-interest processing
• Statistical analysis
• Product learning
• Application-specific detection routines

Different manufacturers use different algorithm architectures.

Therefore, terms such as Lv1, Lv2 and Lv3 should not be presented as universal X-ray inspection standards.

The important engineering objective is consistent:

Detect target foreign objects while minimizing false rejects caused by normal product variation.

Commercial X-ray systems may use different combinations of image-processing algorithms, including contrast, gradient and morphology-based approaches.

 Product Learning and Shielding

Modern X-ray inspection systems can use product-specific settings to distinguish normal product structures from potential foreign objects.

A typical product-learning process may involve:

1. Running representative good products through the machine.
2. Capturing X-ray images of the normal product.
3. Analyzing the normal image characteristics.
4. Establishing suitable inspection parameters.
5. Testing the product using known foreign-object samples.
6. Fine-tuning the inspection settings when necessary.

Product-specific shielding can also help reduce false rejects caused by normal high-density structures within the product or package.

However, shielding must be applied carefully.

If an area is excluded too aggressively, a genuine foreign object located inside that area could potentially be missed.

For this reason:

Good-product samples must be confirmed before learning, and the final product recipe should be verified using known foreign-object test pieces.

Application testing remains essential. Industry guidance also recommends testing representative contaminants before deploying an X-ray system because detectability varies with both the product and contaminant.

From Detection to Automatic Rejection

An X-ray inspection machine does more than identify an abnormal image.

A complete automated inspection process can be understood as:

Detect → Analyze → Track → Reject

After an NG product is identified, the control system must coordinate the timing between the detection point and the rejection point.

Depending on the production line, different rejection methods may be used, including:

• Air blast
• Push rod
• Flap reject
• Diverter
• Drop reject
• Alarm and machine stop

The suitable method depends on:

• Product weight
• Product dimensions
• Package type
• Conveyor speed
• Product spacing
• Production layout
• Required handling method

For this reason, the rejection system should be considered together with the X-ray inspection system rather than treated as a completely separate component.

TOUPACK TTX Series Food X-Ray Inspection Systems

TOUPACK TTX series is designed for food inspection applications where manufacturers need to identify foreign objects within packaged products.

The series provides different inspection channel sizes for different product dimensions and production requirements.

TTX Series Technical Parameters

The supplied technical specifications also indicate:

• Conveyor speed: 10–70 m/min
• HMI: 17-inch German IMI industrial touch screen
• Connectivity: LAN port and USB port
• Working temperature: -10°C to 40°C
• Working humidity: 30%–90%, no dew
• Specified X-ray leakage: <1 μSv/hour
• Protection: Detachable protective curtains
• Alarm system: Alarm and machine stop; rejecter optional
• Power supply: AC220V ±10%, 50/60Hz, 1.5 kVA Max
• Machine frame: SUS304

Important Note About Detection Sensitivity

The detection values above should be understood as reference values based on specified test samples and conditions, rather than a universal guarantee for every food product.

Actual performance may vary according to:

• Product density
• Product thickness
• Package structure
• Foreign-object material
• Foreign-object size
• Foreign-object shape
• Foreign-object orientation
• Conveyor speed
• Inspection settings

For a new application, testing with the customer's actual product and representative foreign-object test pieces is recommended.

Key Features of the TOUPACK TTX Series

Reliable X-Ray Safety Protection

The system uses a shielded inspection structure and detachable protective curtains to help control X-ray exposure around the inspection area.

Cabinet X-ray systems are designed around a shielded enclosure that contains the X-ray source and prevents personnel from accessing the exposure area during X-ray generation. Safety requirements can also include warning indicators, warning labels and interlocks depending on the applicable regulations and system configuration.

User-Friendly HMI

The TTX series uses a 17-inch German IMI industrial touch screen for operator interaction.

A clear HMI helps operators monitor inspection status and manage machine operation.

Strong Environmental Adaptability

The supplied specification supports a working temperature of:

-10°C to 40°C

and working humidity of:

30%–90%, no dew.

The actual installation environment should follow the machine's operating requirements and the conditions specified for the selected model.

Fully Enclosed Machine Structure

The enclosed stainless-steel machine structure provides a practical configuration for food production environments while integrating the X-ray inspection, conveyor and control components into one system.

Data Export and Connectivity

The system supports:

• LAN connection
• USB connection
• Production information export
• Spreadsheet-based data handling
• SPC system connection where supported by the configuration

Automatic Image Saving

Inspection images can be automatically saved according to the configured system settings, providing a useful reference for production review and comparison.

Product Shielding Function

The system provides shielding functions designed to help distinguish normal product or packaging structures from potential foreign objects.

This can be particularly useful when normal high-density structures create image features that could otherwise lead to unnecessary rejects.

Radiation Safety and Food X-Ray Inspection

Radiation safety is a fundamental part of cabinet X-ray inspection equipment.

A cabinet X-ray system places the X-ray source inside a shielded enclosure. FDA describes cabinet X-ray systems as enclosed systems used for applications including industrial quality control and food inspection.

For systems sold in the United States, FDA's cabinet X-ray performance standard includes requirements for radiation emission, shielding-related design and safety features. The FDA standard specifies that external radiation emissions must not exceed 0.5 milliroentgens in one hour at any point 5 cm from the external surface under the specified test conditions.

The exact regulatory requirements applicable to an X-ray inspection machine depend on the destination market.

Does X-Ray Inspection Make Food Radioactive?

No.

An X-ray inspection system generates X-rays electrically; it does not use a radioactive source to create the inspection image.

FDA states that food and other products passing through cabinet X-ray systems can be safely used, and distinguishes cabinet X-ray inspection from the much higher radiation doses used in food irradiation.

Therefore, food X-ray inspection should not be confused with food irradiation processing.

How to Choose the Right Food X-Ray Inspection Machine

Selecting an X-ray inspection machine should begin with the application rather than simply choosing the machine with the highest theoretical sensitivity.

Step 1: Identify the Product

Examples include:

• Snacks
• Nuts
• Frozen food
• Meat
• Seafood
• Ready meals
• Bakery products
• Pet food
• Other packaged foods

Step 2: Identify the Package

Consider whether the product is packed in:

• Pillow bags
• Stand-up pouches
• Premade bags
• Trays
• Cartons
• Cans
• Bottles
• Other flexible or rigid packages

Step 3: Define the Target Foreign Objects

Instead of simply asking for "high sensitivity," define the actual contamination risks.

For example:

Stainless steel + glass + stone + bone

provides a much clearer basis for machine selection and application testing.

Step 4: Define Product Dimensions

Provide:

• Maximum package width
• Maximum product height
• Product thickness
• Package dimensions
• Product weight

These parameters help determine the appropriate detecting width and detecting height.

Step 5: Define Production Speed

The required inspection capacity should be considered together with:

• Product size
• Product spacing
• Conveyor speed
• Detection processing
• Reject response

Step 6: Conduct Application Testing

This is the most important step.

A reliable evaluation should use:

Actual Product + Representative Test Pieces + Target Production Conditions

Published or catalogued sensitivity values can provide a useful reference, but application testing is the best way to establish actual performance.

Frequently Asked Questions

Can a food X-ray inspection machine detect stainless steel?

Yes. Stainless-steel contaminants are among the typical foreign objects targeted by food X-ray inspection systems. The TTX series specifies reference detection values using SUS test balls and SUS wire under its defined test conditions.

Can X-ray inspection detect glass?

Yes. Glass is a common non-metallic contaminant targeted by X-ray inspection. The TTX series technical specifications list a Ø1.0 mm glass test ball as a reference detection value for the models shown.

Can X-ray inspection detect bone?

Certain bone fragments can be detected when sufficient X-ray contrast exists between the bone and surrounding product. Actual sensitivity depends on the product and bone characteristics.

Can X-ray inspection detect plastic?

Certain higher-density plastics can be detectable. Low-density plastics can be much more difficult to identify, so application testing is recommended.

Is X-ray inspection better than a metal detector?

Not in every application.

Metal detectors are highly effective for metal contamination. X-ray systems can additionally identify certain non-metallic contaminants such as glass, stone and bone.

The appropriate technology depends on the product, package and contamination risk.

What is the smallest foreign object an X-ray machine can detect?

There is no single minimum size that applies to every product.

For the TOUPACK TTX series, the supplied specifications provide reference values such as SUS ball Ø0.3 mm for the TTX-2417K100 and TTX-4017K100 models, and SUS ball Ø0.4 mm for the TTX-5026K100 and TTX-6035K100 models.

These values should be interpreted as reference detection sensitivity under specified test conditions, not as a universal minimum detection size for every product.

Does food become radioactive after X-ray inspection?

No. X-ray inspection does not make food radioactive. Cabinet X-ray inspection uses electrically generated X-rays rather than a radioactive source, and FDA distinguishes this inspection process from food irradiation.

Conclusion: Reliable Food Inspection Starts With the Right Application

A food X-ray inspection machine is not simply an X-ray source and detector.

It is a complete inspection system combining:

X-ray generation + detector imaging + image analysis + machine control + product-specific settings + safety protection + automatic rejection.

Its key advantage is the ability to inspect for a broader range of physical contaminants than metal detection alone, including certain non-metallic contaminants such as glass, stone, bone and dense plastic.

At the same time, X-ray inspection has its own technical limitations. Detection performance depends strongly on the relationship between the product and the target contaminant.

Therefore, the most meaningful question is not simply:

"How small an object can an X-ray machine detect?"

A better question is:

"What foreign objects need to be detected, in which product and package, under what production conditions?"

Once these requirements are defined, the appropriate X-ray source, detecting channel, image-processing configuration and rejection system can be selected and validated.

For TOUPACK, the goal is not simply to provide an X-ray machine with a high theoretical specification.

The goal is to provide a practical food X-ray inspection solution that can be evaluated against the customer's actual product, contamination risks and production requirements.