Processing & Cleaning
Machine Cleaned vs Sortex Pulses
The commercial difference between mechanical cleaning and optical colour sorting, what each removes, what the premium pays for, and how to decide which one a contract needs.
· 7 min read
Almost every pulse enquiry eventually reaches this question, and it is usually framed as a quality question when it is really a fit-for-purpose question. Machine cleaned and Sortex are not two rungs on a ladder of care. They are two different process capabilities, and one of them costs materially more because it throws away more product.
What each process can and cannot do
Mechanical cleaning separates on physical properties: size, weight and density. It removes field trash, dust, husk, shrivelled and immature seed, stone, soil, oversize and undersize material, broken pieces and a large share of insect-damaged grain. What it cannot do is see. A seed that is the right size, the right weight and the right density but the wrong colour goes straight through.
Optical sorting adds sight. Cameras assess each grain against an accepted colour range and eject the outliers. That handles the entire category of defects that mechanical cleaning is blind to: discolouration, staining, mould marks, heat damage, off-shade seed and foreign seed distinguishable by colour.
| Parameter | Machine cleaned | Colour sorted |
|---|---|---|
| Purity | 98% min typical | 99–99.5% min typical |
| Foreign matter | 1% max typical | 0.1–0.5% max typical |
| Discoloured seed | Reduced only incidentally | Directly targeted |
| Off-colour / off-variety | Largely unaffected | Directly targeted |
| Insect-damaged | Reduced by density separation | Further reduced where visible |
| Reject fraction | Lower | Higher — this is what the premium pays for |
What the premium actually buys
An optical sorter does not repair a defective grain; it removes it. Everything ejected leaves the contracted lot, and at tighter settings sound grain is ejected alongside genuine defects because no camera judgement is perfect. That yield loss, plus the additional processing time and the capital behind the machine, is the whole basis of the price difference.
It also means "Sortex" is not a single specification. The same machine run at a light setting and at an aggressive setting produces two very different products at two very different costs. This is why a contract should state the target parameters rather than simply the word "Sortex" — otherwise both parties are guessing at the intensity.
Choosing between them
- Specify machine cleaned when
- The buyer mills, dehusks, splits or otherwise processes the product so that the seed coat and its colour become irrelevant; or the destination is price-led and the visual standard is modest.
- Specify colour sorted when
- The end consumer sees the product — retail packs, transparent packaging, food service presentation; or the type is pale-seeded, where every defect is conspicuous; or consistency between shipments is part of what the buyer is selling.
A note on terminology
"Sortex" is a brand name that has become the generic trade term for optical colour sorting, in the way that other trademarks have become generic in their own fields. When a contract says Sortex it means optically colour sorted, regardless of which manufacturer supplied the machine. If a buyer requires a specific technology — for example multi-spectral or near-infrared sorting rather than visible-light sorting — that has to be stated explicitly, because the generic term does not cover it.
How the two levels appear in a working mung bean specification. Mung bean specifications