Helping vegetable processors achieve food safety and product quality

Pre-sorting for foreign materials and critical defects

You name it, and in a load of freshly harvested vegetables, you’re likely to find it. Clods of earth, rocks, stones, sticks, stalks, vines, toxic weeds, field mice, plastic bottles, fragments of glass - all of these things and others get mixed in with vegetables delivered to processing lines. The extent of this problem varies with crop type and field location, but there’s no getting away from it.

This necessitates pre-sorting to remove foreign materials before the vegetables are fed onto the processing line. The more it is possible to sort out at this preliminary stage, the less it will be necessary to do later, enhancing throughputs. TOMRA offers four different optical sorters for vegetable pre-sorting: the Sentinel II, Halo, TOMRA 3A, and TOMRA 5A.

The TOMRA 3A is used mostly for unwashed potatoes (and unpeeled onions), which we’re not considering here, but we’ll take a look at the other three machines.

The Sentinel II combines TOMRA’s pulsed LED/ sensor arrays with a simple user interface to remove a broad range of foreign materials, rodents, defects, discoloration, damage, and undersize product. The Sentinel II’s superior technical specification enables it to outperform competitors in sorting efficiency and sorting capacity. With three different sizes giving a wide capacity range, it’s ideal for seasonal and yearround processors.

Also popular for pre-sorting many types of whole vegetables is the Halo, a high-performance machine that sorts according to size, shape and quality. The Halo uses top and bottom sensor banks to view each individual object in flight using a combination of LED, CCD camera, and nearinfrared. This performs targeted spectroscopy to 1mm precision. The Halo is suitable for carrots, beets, and onions, as well as fresh pack carrots, parsnips, cucumbers, and gherkins. Depending on the application, the Halo increases yield by up to 4%, increases throughput by up to 25%, and reduces labor requirements by up to 80%.

Another machine often used for pre-sorting, and even more efficient than the Sentinel II and Halo at removing foreign material, is the TOMRA 5A. This belt machine employs top and bottom sensor banks to view each individual object in flight using a combination of pulsed LED, camera and near-infrared. As with the Halo, targeted spectroscopy is precise to 1mm - achieving a superior foreign object removal rate of more than 98%. These high efficiencies, combined with low false reject rates, are often a key requirement to protect the cutters in the processing line.

End-of-line quality checks

When processing IQF vegetables, there is a final quality check to be made, either immediately after the freezing tunnel, on the mixing line, or just before the product is packed. This is an additional opportunity to find and remove unwanted materials that were just not visible or were missed when sorting before the product was frozen. For example, there might be remaining carrot slices or dices in the product stream with color or shape defects. Or there might still be some Datura or Nightshade mixed in with frozen peas because these weeds are so similar in appearance to the acceptable product and sometimes only possible to detect with our BSI+ technology. Another example is that there can be small embedded stones present inside of soft diced vegetables like eggplant or zucchini.

Three machines are typically assigned to handle these checks: the Ixus Bulk, Blizzard, and Nimbus BSI+.

The Ixus Bulk scans product in bulk to detect dangerous foreign materials - such as metal, glass, and small rocks - which that may be freeflowing in the product stream or embedded in the product. This machine has been engineered around the best performing x-ray detector for unmatched image resolution, resulting in the ability to find the smallest defects at high throughputs.

The Blizzard, a free-fall sorter with a small footprint, does its detection work with pulsed LEDs and a combination of cameras. Optimally positioned after IQF tunnels or on packaging lines, this machine’s lighting system generates little or no heat in the cold environment and needs very little calibration or maintenance. The LEDs’ different wavelengths detect unwanted foreign material, misshapen product, and discolored product.

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