Bühler doubles the resolution to boost foreign object detection

By Joseph James Whitworth contact

- Last updated on GMT

InGaAsHD cameras have double the resolution compared to Enhanced InGaAs ones
InGaAsHD cameras have double the resolution compared to Enhanced InGaAs ones

Related tags: Fruit

Bühler has developed cameras for its optical sorters that it claims can detect foreign objects smaller than ever before.

The InGaAsHD​ cameras for the Sortex E range of optical sorters have double the resolution compared to its Enhanced InGaAs cameras.

They will be used on the Sortex E1D for the fruit and vegetable sector, the Sortex E1C which is a similar machine and Sortex A for the nut industry.

The firm said the high definition cameras are able to detect foreign materials down to half the size previously possible, resulting in better detection and removal.

Doubling the resolution

Stephen Jacobs, global product manager at Buhler Sortex, said double the resolution means it is able to see many more pixels on smaller objects and seeing more of the products means there is less chance to miss anything.

Bühler Sortex E with InGaAsHD technology

“No machine can take out 100% of defects or foreign material. If it is a very small piece, especially if it is the same or similar colour to the product, it is possible that it would be missed,” he told us.

“Foreign material is the more serious contaminant that needs to be removed as it could for example be a choking hazard or break a tooth etc. As we improve the difference between foreign material and good product we reduce the amount of good product removed (yield loss).

“Foreign material removal is taken seriously with all commodities. Fruit and vegetables can be more difficult to sort due to some complex mixes of different products with a wide variety of colours making conventional sorting by colour almost impossible.”

With consumers increasingly demanding convenient and fast-to-prepare foods, frozen fruits and vegetables, such as green peas, beans or berries, are a growing market segment. At the same time, food safety regulations are tightening and consumers expect an impeccable product, said the firm.

Among the safety concerns are foreign materials, such as small stones, pieces of wood and glass, or slivers of plastic. If contained within packaged frozen food products, they will pose health risks - including lacerations, choking or broken teeth.

For food processors, they may result in expensive product recalls and damage to reputation.

Camera specifics

The cameras can separate foreign materials from good product of the same colour as they are based on semiconductor sensors made from indium gallium arsenide alloy and operate in the short wave infra-red range (SWIR).

This means they are able to detect subtle colour differences that cannot be seen in the visible spectrum.

The technology is for use in the packing line, as a final check, to ensure that difficult–to-detect packaging materials such as light coloured wood in potatoes, cardboard in carrots and coloured plastic in vegetable mixes, were identified and removed from the product stream.

“By combining a new hardware, software and lens package, we were able to engineer a new camera with double the resolution. As a result of this in-house development, our sorter will be able to identify foreign material objects down to half the previous size,​” said Benedict Deefholts, head of sensor development at Bühler.

Processors that are already operating Sortex E optical sorters with Enhanced InGaAs cameras will be offered an upgrade option.

Walnut specialists using Sortex E BioVision

Meanwhile, Bühler has revealed some customers using its Sortex E BioVision - one piece of equipment that does the job of two conventional machines – sorting for defects and foreign material.

buhler SORTEX E BioVision
Buhler Sortex E BioVision

The optical sorter, launched last year, has been installed at Moldovan specialist nut grower and processor Monicol, and Californian walnut processor Andersen Nut Co.

Monicol approached Bühler to remove hazardous material, mainly shell and foreign material such as sticks and stones, as well as dark colour defects – the most common defect in walnuts.

Dumitru Vicol, CEO of Monicol, said: “The trials were conducted on product with input contamination ranging from 10% to 34%, achieving accept quality of 99%.

“On trials of input contamination at 15%, the accept quality rose to 99.9%, with no shell found per 1kg. A typical customer requirement allows for one piece of shell in every 10kg, so we were very happy with these results.”

Andersen Nut Co. was contending with sorters operating at low capacity, with lengthy processing times, which meant high production costs.

It was sorting walnuts to remove shell, discoloured nuts and rancid products, which often meant between six and eight passes through equipment before product could be passed to the hand-picking tables.

Dan Andersen, of Andersen Nut Co, said: “The Sortex E BioVision proved to achieve the same levels of quality and better yields in just two to four passes, which achieved higher volumes. It was also able to target all defects effectively. What’s more, production volume increased because the machine was able to handle higher capacity.”

BioVision detection technology analyses the spectral and spatial difference between walnut meat and shell to distinguish differences between shell varieties and walnut meat.  

Related topics: Food Safety & Quality

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