Every agri specification should include a maximum moisture, a minimum purity and a maximum foreign matter, each with a named test method. Most buyers also add limits for admixture of other seeds, damaged seeds and insect damage.
There is no single correct figure for any of these. The right limit depends on the product, the grade, how you will use it and what your market and customers require.
Moisture
Moisture affects weight, shelf life and safety. Too much moisture lets mould grow and raises the risk of aflatoxin and ochratoxin. It also means you pay for water.
Write moisture as a maximum, for example "moisture: max X% by weight", with the method stated. For illustration only, a line might read "moisture: max 10% (oven method)", but your figure should come from your customer's spec or the standard you buy to.
Say where moisture is measured. Product tested dry at the factory can pick up moisture in a humid container. Some buyers test both before loading and on arrival.
Purity
Purity is the share of the sample that is the product you ordered, after removing everything else. It is written as a minimum, for example "purity: min X%".
Purity grades are often how seed spices are traded in India, and a higher grade usually means more cleaning or sorting. Ask what purity a machine-cleaned or sortex-cleaned grade normally achieves for that product, then confirm it on samples.
Foreign matter and related limits
Foreign matter is anything that is not the product. Define it clearly, because suppliers and labs may sort it differently.
- Extraneous matter: stones, soil, dust, stalks, husk and other non-seed material, written as a maximum.
- Admixture: seeds of other plants, written as a maximum and kept separate from extraneous matter.
- Damaged and discoloured seeds: broken, shrivelled or off-colour seeds, written as a maximum.
- Insect damage: bored seeds, live or dead insects, written as a maximum, often with "no live insects".
- Stones and glass: many buyers write "nil" for these because of the risk to equipment and consumers.
How to set your own figures
Tight limits cost more because they need more cleaning and more rejected material. Loose limits cost you later in cleaning losses or customer complaints. Find the point that suits your use.
Remember that results vary with the sample. A small sample from one bag can pass while the lot fails. Say how many bags are sampled and how the samples are combined.
- Start from your customer's spec and your country's food law.
- Look at any official or trade standard for the product that your market refers to.
- Ask two or three processors what they normally achieve for the grade, and test their samples.
- Add a line on test method and sample size for every parameter.
- Agree in advance what happens when a result falls just outside the limit.
Put the numbers in context
Tolerances only work as part of a full spec. Our guide to writing an agri product specification covers the rest, including contaminants and microbiology.
How we help
We help you set limits the product and grade can meet, then draw sealed samples and have them tested against those limits at an NABL-accredited lab. Send your current spec for a free sourcing review.