How to compare soy protein concentrate specifications

Start with the reporting basis for protein

A protein result is only comparable when you know how it is reported. An as-is result describes the product as tested, including its moisture. A dry-weight result removes the effect of moisture mathematically, so it compares the solids in samples with different moisture levels. The same lot can therefore have a lower protein percentage as-is than on a dry basis without any change to its protein content.

To convert an as-is protein result to a dry basis, divide it by the solids fraction: dry-basis protein = as-is protein × 100 ÷ (100 − moisture percentage). Before comparing supplier offers, establish which basis your requirement uses and whether both results use that basis. If a result’s basis is missing, it cannot be compared reliably with a stated dry-basis requirement.

Also note the analytical method and calculation used for protein. Many protein tests estimate protein from nitrogen, so the method and nitrogen-to-protein conversion factor can affect the reported result. A number without its method may look precise but still leave an important comparison unresolved.

Read moisture, ash and crude fiber as separate measures

Moisture is not a substitute for protein basis: it is the measurement needed to understand that basis and also describes water in the product. Its relevance depends on the product’s specification and the buyer’s handling and storage needs. Compare moisture results reported using the same method and sampling context, and distinguish a lot result from a contractual maximum.

Ash is the material remaining after the sample is incinerated and is used as a measure of total inorganic residue. It does not identify individual minerals or explain their source. For a meaningful comparison, check whether the result is reported as-is or on a dry basis, and whether the test method matches the requirement.

Crude fiber is an analytical fraction, not a complete measure of dietary fiber. Its result depends on the method used and should not be treated as interchangeable with total dietary fiber or other fiber measurements. A low crude-fiber result alone does not establish that two concentrates will behave alike in a food or feed formulation.

Keep food standards, lot analyses and feed specifications distinct

A Codex food standard and a supplier’s certificate of analysis serve different purposes. A food standard defines requirements for products within its scope and context; it is not automatically the specification for every offered lot. A certificate of analysis reports results for a sample or lot, and those results need to be compared with the actual purchase specification using consistent methods and reporting bases.

Feed specifications have a different purpose: they support ingredient evaluation and formulation for a particular feed use. They may set out nutritional or quality measures selected for that use, but a feed specification is not interchangeable with a food-standard requirement. Do not apply a food threshold to a feed product, or the reverse, without establishing that the product category, intended market and governing requirement match.

Numerical limits require context. Before using a threshold in a purchase contract, identify the applicable product definition, market or jurisdiction, intended use, measurement basis and analytical method. If any of those differ, a threshold copied from another standard or offer may not provide a valid comparison.

Build a like-for-like comparison

Put each offer into a common comparison format: product identity and intended use; protein result and reporting basis; moisture, ash and crude fiber results with their bases; analytical methods; and the relevant specification limits. Keep a supplier’s stated guarantee separate from the reported test result. A limit describes what the product is required to meet; a lot result describes what was measured in a particular sample.

Then check that the methods answer the same question. If one protein result is dry basis and another is as-is, convert only when the moisture result is available and the conversion is appropriate. If methods differ, ask whether the results can be interpreted against the same acceptance criterion rather than assuming the figures are equivalent. For ash and crude fiber, compare method and basis as well as the number.

This approach is more useful than ranking concentrates by protein percentage alone. The right specification depends on whether the product is destined for food processing or feed formulation, and on the buyer’s actual acceptance criteria. Once those requirements are defined, use the soy protein concentrate page to pursue a bulk sourcing inquiry.

Common questions.