MICROWAVE TECHNOLOGY FOR THE DETECTION OF PHYSICAL CONTAMINANTS IN PACKAGED PRODUCTS

 

Microwave technology can detect in-line physical contaminants (plastic, glass, metal, wood, insects, stones, etc.) on packaged and/or bottled products that cannot be detected by currently used technologies (X-rays, metal detectors).

This type of inspection, developed by Antares Vision Group, will revolutionise the in-line contaminant inspection market by meeting increasingly stringent food safety requirements.

 

TECHNOLOGIES CURRENTLY USED TO DETECT PHYSICAL CONTAMINANTS

There are several solutions for the detection of physical contaminants, some of which can be applied in the pre-production phase, before the raw material arrives at the processing plant, and others integrated into the production line, such as inspection. The most effective check to ensure that the product is free of foreign objects is carried out after packaging, when the product is closed and sealed.

And it is at this stage that the most widely used technologies to date, metal detectors and X-rays, come into play, However, these technologies have inherent limitations in detecting foreign objects:

- Metal detector: is capable of detecting metal, although it has difficulty with very thin, needle-shaped, or very small metals.

- X-ray: is more effective than the previous because it detects a wider range of contaminants.

In addition to metals, it detects some types of plastic (not low density), but does not always detect bone and rubber, fruit pits or petioles, and does not detect insects and wood. The inspection machine must also be certified to ensure the safety of the operator and the working environment.

environment, as ionising radiation is used by the X-ray generator.

It is evident that many contaminants that are currently problematic for industry are not detected by current solutions.

Therefore, there is a need for integration with new technologies that are more effective in detecting multiple problematic contaminants for the food and beverage industry through new inspection machines at the final inspection stage of the packaged product.

 

MICROWAVE TECHNOLOGY TO DETECT FOREIGN OBJECTS THAT CANNOT BE IDENTIFIED BY X-RAY AND METAL DETECTORS.

Microwave technology is completely new and will revolutionise the in-line quality control and product safety market for the food and beverage industry.

The operating frequency range is a completely safe band which operates at very low power levels and is already used by many electronic devices in everyday use.

This technology proposes a new detection principle: It is based on the dielectric contrast between the product to be inspected and the potential contaminant, and not on the difference in density as in the case of X-rays. The dielectric contrast depends on the difference in relative permittivity, a physical property of each type of material.

It can be defined as a measure of electrical polarizability, i.e., how the material reacts to the application of an electric field. The difference in relative permittivity is very high between certain contaminants and the food or beverage product to be inspected.

Note the extreme effectiveness of the technology on metal, which, as a conductor, will be detected in all shapes and sizes as there will always be a very high permittivity difference.

 

HOW MICROWAVE TECHNOLOGY WORKS

The system consists of antennas, designed to operate at the desired frequency, which surround the product. During the analysis time, on the order of hundredths of a second, it is possible to detect the signals exchanged between these devices, after passing through the product to be analysed. In this way it is possible to monitor any change in the electric fields emitted, due to the possible presence of a contaminant.

The acquired signal is processed using Artificial Intelligence (AI) techniques, which therefore require a "training" phase: the robustness of the classifier is verified by evaluating its ability to detect foreign objects, even if they are different from those used for this initial calibration phase.

In an advanced version of the system, other functions can be introduced through additional processing of the same signal acquired and used for binary classification of the product.

Using ad-hoc developed algorithms, it is possible to reconstruct a three-dimensional image of the product: a 3D map of the dielectric contrast in the volume being analysed, which, in other words, corresponds to the position of the contaminant in the product.

 

PERFORMANCE OPTIMISATION PARAMETERS

To optimise performance, the inspection device considers the following aspects:

1 - The dielectric contrast, which depends on the permittivity ratio between the product and the contaminant;

2 - The physical dimensions of the product to be analysed;

3 – The central operating frequency of the microwave used to ensure correct penetration into the product;

4 - Optimisation of the position of the sensors around the product to maximise its 'illumination'.

 

THE APPLICATIONS FOR MICROWAVE TECHNOLOGY

Microwave technology for packaged products can be applied to many products in the food and beverage industry, from tomato sauce in glass jars or pesto, jams, champagne bottles to wine and beverages in general: these are just a few examples of applications. The optimal products to be analysed are liquid, semi-liquid (such as creams) or homogeneous, homogeneous from the point of view of permittivity.

The only real limitation relates to containers made entirely of aluminium (cans) or poly-bonded packaging in which aluminium is present.

However, for containers with twist-off caps or aluminium foils, it is possible to use a different arrangement of antennas around the container to allow the microwaves to penetrate the product.

 

ADVANTAGES AND LIMITATIONS OF MICROWAVE TECHNOLOGY

The technology can be used in-line because it can make measurements in tenths of a millisecond. It does not pose problems in terms of pollution of the working environment or protection of workers, as it does not emit ionising radiation.

Furthermore, with the low power used in the milliwatt range, it does not heat the product or the container, thus guaranteeing its integrity.

The inherent limitation of the technology itself is the inability of microwaves to penetrate the inside of all-metal packaging.

 

THE MAIN CAUSES OF PHYSICAL CONTAMINATION OF FOOD AND BEVERAGES

 

Despite considerable efforts by manufacturers to prevent risks, including the use of increasingly sophisticated control systems, physical contamination of packaged products continues to have a significant impact on manufacturers.

Reports from the Rapid Alert System for Food and Feed (RASFF) confirm the existence of this issue for many types of products, contaminated with foreign objects of various compositions such as glass, metal, plastic, and insects and, to a lesser extent, bones, stones, wood, and rubber.

The types of contaminants reported so far are precisely those that cannot be detected by current technologies, except for metal, which is likely to have a high number of reports due to foreign objects associated with in-line production operations.

 

There are three main sources of contamination:

1 - contaminants that come directly from the field when the raw materials are harvested,

For example, in the case of fresh produce such as fruit and vegetables, which may be ground or processed into fillings or sauces.

The most common materials in this case are stones, insects or small animals, seeds, or wood of various kinds;

2 - transport-related contaminants;

3 - contaminants from the production process, such as metal from the production line itself due to malfunctions in the packaging or bottling systems, which may result in fragments of the container inadvertently contaminating the product.

Other contamination may be related to the presence of operators on the line (e.g., gloves, cloths, etc.) or the presence of unwanted material on the product itself, such as bones.

 

RISKS ASSOCIATED WITH PHYSICAL CONTAMINATION

The potential risks associated with the presence of foreign objects in food and beverages concern the health of the consumer: this could be the ingestion of a piece of glass or other contaminants. All these incidents result in economic damage with a negative impact on brand reputation and consumer confidence, not to mention the impact of associated legal costs.

This is therefore an issue that has a significant impact on the food and beverage market, constantly looking for technological solutions and inspection systems to complement existing ones capable of detecting physical contaminants that today's solutions cannot.

 

CONCLUSIONS

Microwave technology makes it possible to inspect bottled or packaged products for physical contaminants previously invisible to X-rays or metal detectors, such as plastic, glass, metal, wood, rubber, bones, stones, insects, etc.

This is a revolutionary technology for the F&B market that meets the industry's increasingly stringent food safety requirements.