Dry-matter and as-sold protein percentages describe the same material on different bases. Learn how moisture affects the calculation and what to align across a whey protein isolate 90 specification and lot COA.
A protein result reported “as sold” describes the product in the condition tested, including its moisture. A dry-matter result expresses protein after mathematically removing the moisture contribution. The two figures can therefore differ even when they describe the same sample: water makes up part of the as-sold weight, while dry-matter reporting compares the material excluding that water.
For a bulk buyer, the distinction matters when comparing a supplier specification with a lot certificate of analysis (COA), or when evaluating offers that use different reporting bases. A higher percentage on a dry basis is not automatically evidence of a higher-protein lot; it may simply reflect a different calculation basis.
When protein and moisture are expressed as percentages of the same sample, the calculation is straightforward. Dry-matter protein percentage equals the as-sold protein percentage divided by the percentage of dry matter, then multiplied by 100. The dry-matter percentage is 100 minus the moisture percentage.
For example, a buyer would need both the as-sold protein result and the moisture result from the same sample to calculate a dry-matter equivalent. The reverse calculation multiplies dry-matter protein by the dry-matter fraction. These calculations align reporting bases; they do not replace the laboratory’s result or establish that a lot meets a purchasing specification.
Start by identifying the basis attached to every protein value: as sold, as-is, or dry matter. Do not infer the basis from a product name or a number in a product description. Then check whether moisture is reported on the same COA and whether it belongs to the same lot and sample as the protein result. Without those details, a conversion or direct comparison may be unreliable.
Next, compare the protein test method. Laboratories may use different methods or calculation conventions, so two values should not be treated as equivalent solely because both are labeled “protein.” Ask which method was used and, when applicable, how measured nitrogen is converted to a protein result. For a purchasing specification, align the required method and reporting basis with the COA before comparing results.
Also distinguish the specification’s acceptance limit from a typical or target value. A specification sets the criterion an offered lot is expected to meet; a COA reports results for a particular lot. Check the units, basis, rounding, and any stated tolerance, then assess the lot against the specification on that same basis. A rounded COA value near a limit may need clarification about the unrounded result or the applicable acceptance rule.
A useful comparison records the product identity, protein result, reporting basis, moisture result, test method, and whether the number is a specification limit or a lot result. If an offer and its COA use different bases, request the missing information needed to compare them consistently rather than ranking the offers by the headline protein percentage.
Before sourcing whey protein isolate 90, define the protein requirement in the terms your quality team can evaluate: test method, reporting basis, and how moisture relates to acceptance. Then compare the proposed specification with the lot COA using those same terms. See the [Whey Protein Isolate 90 page](/ingredients/whey-protein-isolate-90) for sourcing once the required basis and quality measures are clear; lot-specific results and commercial terms need to be established for the offer.
When the sample contains moisture, removing that moisture from the calculation increases the percentage relative to the original as-sold weight. The result is a different reporting basis, not proof that the product contains more protein in the delivered condition.
Only if the results use comparable reporting bases, test methods, units, and calculation conventions. If one is as sold and the other is dry matter, align the basis using a corresponding moisture result before comparing. Also confirm whether each number is a lot result or a specification limit.
Ask the supplier to identify whether the result is as sold or on a dry-matter basis, name the test method, and provide the relevant moisture result for that lot if a conversion is needed. Without these details, the protein figure cannot be compared confidently with a specification stated on a different or unspecified basis.
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