Game-changing sorters are fighting the threat of toxic weeds in green vegetables

Toxic datura and nightshade weeds are more often harvested with crops such as green beans and baby leaf spinach, with the risk of getting into the final product. However, an advanced sorting technology is proving to be a game-changer. Jacob Hobbel, TOMRA Food’s Global Category Director for Vegetables & Fruits, explains how to mitigate this risk.

Of all the threats to food safety found on processing lines, toxic weeds are among the hardest to deal with. When poisonous datura or nightshade plants get mixed with green vegetables, the weeds are so similar in color to the product that they are difficult to detect. This is especially true of green beans and baby leaf spinach – and after the beans are blanched for freezing, or the spinach is cut, datura becomes even harder to detect and reject.

This has always been a challenge for processors, and now, changes in farming methods are making the problem more widespread. Increasing consumer demand for organically-grown crops, plus tightening limitations on pesticide use, are resulting in weeds becoming more prevalent. And this will only get worse: global sales of organic foods are expected to increase in annual value between now and 2030 at an extraordinary compound annual growth rate of 10% to 13%. This will lead to even more toxic weeds getting mixed up with fresh and frozen vegetables.

Retailers are concerned about this. If consumers find their food products contain poisonous foreign materials, big brands could face expensive compensation claims and even costlier reputational damage. This means that retailers expect food processors to take all necessary steps to eliminate these risks.

The good news is that state-of-the-art sorting machines provide highly effective solutions. One type of sorting technology, in particular, possesses detection capabilities that only a few years ago were unheard of.

Toxic weeds differ

Nightshade has the appearance of a small green ball that, over time, turns black, ultimately resembling a blueberry. Because there is almost no discernible color difference between green nightshade and green produce, it is difficult for color sorters to detect. And when nightshade gets sliced on a processing line along with green beans or baby leaf spinach, it is also difficult to differentiate by shape.


Datura is also small and ball-shaped but stays green and has many small spikes. As well as being hidden from color sorters when mixed with green vegetables, this weed is also very difficult to identify by shape after it has been blanched with green beans because this causes it to lose its spikes.


These various challenges mean that sorting out nightshade and datura by color and shape is not always enough. Often, it is also necessary to sort the objects passing down a processing line according to their biological characteristics – an advanced capability that has proven to be a gamechanger.

Sorters solve the problem

The company that introduced this ground-breaking capability, revolutionizing the detection of toxic weeds in vegetables and fruit, as well as bringing unrivaled sorting capabilities to other food categories, is TOMRA Food. As the industry leader in optical sorting and grading solutions for the food industry, TOMRA offers highly effective sorting solutions for every type of vegetable product, including IQF, fresh pack, fresh-cut, and canned.

Although the primary purposes of optical sorters are to protect food safety and deliver consistent product quality, they also deliver many other advantages. The best sorters can grade to specification, increase removal efficiency, minimize false rejects, reduce the need for manual intervention, help solve labor scarcity problems, reduce line downtime, and provide valuable data about the sorted product. As a result, food waste gets reduced while yields and profits are enhanced.

The two sorting machines best suited to detecting and rejecting toxic weeds are the TOMRA 5B and the TOMRA 5C. Some processors use both these machines on the same line: the TOMRA 5B first, before the product is sliced or blanched, then the TOMRA 5C, with Biometric Signature Identification (BSI) technology, to make final checks between the IQF tunnel and the packing station.

TOMRA BSI technology

TOMRA 5B for fresh produce

The TOMRA 5B is a high-end belt sorting machine that can detect and reject datura and nightshade weeds when mixed with fresh product. Combining 360-degree surround-view camera technology with one or more lasers and advanced shape algorithms, this machine sorts by color, shape by cameras, and structure by laser. It detects up to 99% of foreign material and is ideal for the targeted identification of extremely small individual defects in high-volume production flows.

Operators like the TOMRA 5B's intuitive touchscreen user interface, which shows critical sorting information and real-time process data. This means fast adjustments can be made at any time so that the operator is always in control and can quickly optimize the sort. Users also appreciate the Health Check feature, which automatically informs the operator before sorting if any of the machine’s surfaces need cleaning. This reduces the risk of line disruptions caused by dirt sticking on the window between the camera/laser and product stream.

TOMRA solutions at VIRTO group

As well as being ideal for sorting green beans and baby leaf spinach, the TOMRA 5B is also used for a wide range of other products: peas, carrots, spinach, corn, bell peppers, fresh-cut baby leaf lettuce, mixed lettuce, potatoes, french fries, chips (crisps), and specialty potato products.

One of the many businesses using the TOMRA 5B for green beans is McCall Farms, one of the USA’s leading providers of farm-fresh canned vegetables and fruit. When using low-cost sorters from manufacturers other than TOMRA, too many defects were getting through with the green beans for Grade A product. But all this changed when McCall Farms switched to the TOMRA 5B.

McCall’s Maintenance Superintendent, Amanda Salisbury, explains: “The performance superiority of TOMRA’s sorters is staggering. It’s a delight to watch them perform. We got results above expectations – a 99% removal rate for all defects. Our product quality has risen substantially. We can now produce a consistently high-grade product while maintaining our preferred production speed. This has played an essential role in boosting production volumes – a 16-fold increase in just four years.”

TOMRA 5C with BSI+ for frozen products

The TOMRA 5C is a premium optical sorter that can detect and reject nightshade and datura in IQF vegetables even after the weeds are reduced in size by slicing and even after datura has lost its spikes when blanched – and it complements its detection work with ultra-low false-reject rates. Unrivaled sorting accuracy is achieved by combining industry-leading sensors and high-resolution lasers with TOMRA’s unique Biometric Signature Identification (BSI and BSI+) technology, AI machine learning, and big data analysis.

With BSI, every object passing down the processing line is assessed for color, shape, and biological characteristics. By looking inside materials with next-generation spectral imaging, then comparing what’s ‘seen’ to information stored in a database, BSI clearly contrasts good and bad materials and can detect smaller defects than conventional spectral technology.


With AI machine learning, the TOMRA 5C continually improves the accuracy of its defect detection. AI also empowers defect classification software, including a one-click button, so machine operators can set new sorting programs with a precision previously only attainable by service engineers.

Big-data analysis is made possible by connecting the TOMRA 5C to the customer portal and cloudbased data platform TOMRA Insight. By accessing live data from the sorter, operators can easily improve line efficiencies. And by accessing data retrospectively, it is possible to quantify the standards of raw materials from suppliers and to make better-informed business decisions.

One of the biggest users of BSI+ technology is Virto Group, a leading producer of quick-frozen vegetables with 15 specialty centers in 10 countries. Virto recently updated its main plant in Spain, with eleven BSI+-equipped sorters. These are located on five single production lines and three double lines.

Virto Group’s Technical Manager, José Antonio Baldero, says: “Our main objective was to take a quantum leap in new technologies for foreign material sorting. We wanted to be able to offer even better product quality to our customers. We opted for TOMRA’s BSI+ because we saw that it is more advanced than the competition’s technology. This is true not only for the detection of foreign materials – with TOMRA’s technology, we have also been able to expand to other product specifications.”

Francisco Casas, who is in charge of sorting at Virto, says the company was quickly impressed by the BSI+ technology because of its high performance, easily configurable programs, and low false rejection rates. “Our new TOMRA units,” he says succinctly, “can do things that were complicated before we had them.”

TOMRA BSI technology

That is what the best sorting solutions do: they make the impossible possible and the complicated easy. And by removing toxic weeds from green vegetables with unprecedented effectiveness, the best sorters also remove worries about food safety and brand reputations.

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