A wheat contract may look clear once protein, gluten, falling number and mycotoxins are listed. In practice, each figure carries a method, a basis, a sample and a laboratory.
Protein 12.5% min answers only half the question. The parties also need to know how the result is measured, on what basis it is expressed, and who analyses which sample.
Under GAFTA No.130, the reference method for protein in cereals is Kjeldahl under ISO 20483. Other methods and standards also exist, including Dumas, ICC, AACC, GOST and national methods. The basis matters as well: protein as is and protein on dry matter basis are not the same figure.
Gluten can be wet or dry. These are different parameters. A clause saying gluten 23% min without more is an invitation to an argument.
Under GAFTA No.130, the reference method for wet gluten is the mechanical method under ISO 21415-2. The manual method can be used as an alternative only if agreed.
Falling number is connected with alpha-amylase activity and sprouting. The result is sample-sensitive: a few sprouted grains in the test portion may change the picture.
Mycotoxins create a similar sampling problem. They are not distributed evenly through a parcel. One part of the lot may be almost clean, while another may exceed the limit. The result may depend on where the probe went, how many incremental samples were taken, and what reached the laboratory test portion.
Not simply: gluten 23% min. Better: wet gluten 23% min as per ISO 21415-1. Not simply: protein 12.5% min. Add the method and basis.
Small letters in brackets next to protein or gluten look harmless until a dispute starts. Then they may decide whether a party has a claim, a defence and a workable arbitration position, or only two certificates with different numbers and genuine indignation.