07 Jan 2020
dried fruits x-ray inspection

Dried Fruits X-ray Inspection in Cereal Mix – Granola, Muesli

LWX technology ensures the detection of even very small foreign material in raw food products that are transported continously on a conveyor belt, and is therefore a perfect choice for dried fruits X-ray inspection.

The most common way of inspecting raw food products is inspecting the product pre-packaging. For products such as dried fruits, cereals or mixes of the two, for example muesli, granola, etc., the ingredients are fed in through a dispencer unit that ensures an even distribuion and product placement of the conveyor belt. Next, the product is ran through the inspection system at a speed up to 25 m/min with a product layer height of 2-3 cm.

When the X-ray systems takes a digital image of the product, this gets analyzed by a special image analysis software. If the system detects a foreign object, the system’s PLC will trigger a signal to the sorting units that are connected to the production line or mounted on the X-ray system’s conveyor. This is the way raw food products are typically rejected, most commonly in portions.

Fig.1. On the left, HYMCIS X Raw food inspection system for products in bulk. Ideally, this type of products should be inspected before the packaging process in order to increase accuracy, but also minimize product waste. On the right, image demonstrating an example of infeed system for this type of product. 

Fig.2. Illustration of the process during quality inspection of unpackaged raw food products. The X-ray system scans the product in sequences of 100-150 gr. In case one of the sequences contains a foreign object, that specific portion will be rejected. 

Mixed products such as muesli, granola and cereal blends contain various products of different origins. In order to ensure accurate quality control, each ingredient should be optimally scanned individually, before mixing them together. The reason why this method is adviseable is because certain ingredients present a higher risk of contamination with foreign material than others.

Our expertise indicates that dried products with a higher sugar content, such as dried fruits, are more prone to physical contamination with foreign material than cereal grains and nuts. InnospeXion has provided in the past X-ray systems for the inspection of blueberries, ananas, papaya, raisins, dates and other dried fruits. For this type of food products, a quality inspection is critical since foreign objects can simply ”stick” to the good product due to its sugary content.

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When this type of raw food products are inspected, the system splits the sequence in multiple frames, and takes a picture of a product portion of about 100-150g. This image will subsequently be analyzed by the software, and in case of contamination, the image will be saved and a signal will be sent to the system’s PLC. The PLC will register this input and send the signal to an I/O terminal connected to an actuator which subsequently activates a one of the sorting units, for instance a sorting flap. The contaminated product portion is rejected when going through the sorting system.

Fig.3. Example illustrating the detection of a small stone (approximately 1,4 mm long and 1 mm wide). The side by side images show the unmarked foreign object between the dried blueberries (on the left), and the second image (on the right) shows the detected foreign object that is marked with red. The difference between the two images is simply an adjustment to the contrast, a function that our system performs is order to delimit and highlight the object with a different density than the main product that is being inspected.

The portion that is sorted out corresponds to the portion captured by the image, showcased having the foreign object as the center of that image. This ensures the highest precision and the lowest possible waste in the sorting. This procedure ensures the higher detection precision while minimizing product waste.

Fig.4. This is how the small stone that has been detected in Fig. 3. looks like during the software image analysis. Our system compares and analyzez the difference in the grey level values of a dried blueberry, and the ones in a stone. As it can be observed in the image, the values have a sudden drop indicating the presence of a foreign object in the mixture.