Stevia Knowledge Center | Episode 8

How to Read a Stevia COA: 7 Key Parameters Buyers Should Check

--A Practical Guide to Evaluating Steviol Glycoside Quality Before You Buy

30-Second Read

A Certificate of Analysis (COA) is one of the most important technical documents when purchasing steviol glycosides.

However, simply checking whether a product says "95%" or "98%" is not enough.

A professional evaluation should look at the product specification, glycoside profile, analytical method, moisture, contaminants,

microbiological parameters, and batch traceability together.

For buyers, the key question is not:

"Does this COA look good?"

It is:

"Does this COA provide enough information to understand exactly what I am buying?"

This guide explains seven important areas buyers and R&D teams should review when evaluating a stevia COA.

1. Start With the Product Specification

The first thing to check is surprisingly simple:

What exactly is the product?

"Stevia 95%" is not a sufficiently precise description.

A COA should clearly identify the product and its specification.

For example:

·Steviol Glycosides

·Reb A 95%

·Reb A 97%

·Reb A 98%

·GSG

·Reb M

This distinction matters because "95% total steviol glycosides" and "95% Reb A" are not the same specification.

Under the EU specification for steviol glycosides from stevia (E 960a), the additive is defined as containing at least 95% of specified steviol glycosides in any combination and ratio, on a dried basis.

Therefore, when comparing two COAs, never compare the headline number alone.

First ask:

95% of what?

2. Look Beyond the Headline Purity

This is where many buyers make their first mistake.

Imagine two suppliers provide:

Supplier A

Steviol Glycosides: ≥95%

Supplier B

Rebaudioside A: ≥95%

At first glance, both appear to offer a "95% stevia."

But they may represent very different glycoside compositions.

The EU specification itself illustrates why this matters: the 95% requirement for E 960a covers a defined group of steviol glycosides, which may be present in different combinations and ratios.

Therefore, buyers should ask suppliers for the detailed glycoside profile, not only the total assay.

3. Check the Glycoside Profile

For stevia ingredients, the glycoside profile can be just as important as the total assay.

Depending on the product, a COA or technical specification may provide information on compounds such as:

·Rebaudioside A

·Stevioside

·Rebaudioside B

·Rebaudioside C

·Rebaudioside D

·Rebaudioside M

·Other related steviol glycosides

Why does this matter?

Because different steviol glycosides have different molecular structures and can produce different sensory characteristics.

This is one reason why two products with similar total steviol glycoside content may not perform identically in an application.

For formulators:

Purity tells you how much of the relevant glycoside family is present.

The glycoside profile tells you what that family actually consists of.

That distinction is extremely important when evaluating taste and application performance.

4. Check the Analytical Method

This is one of the most overlooked parts of a COA.

A number without a test method does not tell the complete story.

For example:

Reb A: 97%

The next question should be:

How was Reb A measured?

Professional evaluation should consider:

·Analytical method

·Test conditions

·Calculation basis

·Reference standard

·Reporting basis

This becomes especially important when comparing suppliers.

If two suppliers report "97% Reb A" using different analytical approaches or calculation bases, the numbers should not automatically be treated as perfectly equivalent.

A good rule:

Always compare the result together with the method and specification basis.

5. Check Moisture - and Understand the Basis

Moisture is another parameter worth reviewing.

Water content can affect:

·Storage stability

·Powder handling

·Physical properties

·Calculation on a dry basis

This is particularly important because some steviol glycoside specifications are expressed on a dried basis.

For example, the EU specification for E 960a states its 95% glycoside requirement on a dried basis and separately specifies a maximum loss on drying of 6%.

This means buyers should understand whether a reported assay is:

As-is basis

or

Dry basis

Otherwise, direct comparison between different COAs can become misleading.

6. Check Safety and Purity Parameters

A COA should not only tell you how much sweetener is present.

It should also provide evidence that the material meets relevant safety and purity requirements.

Depending on the product specification and market, parameters may include:

Heavy Metals

·Lead

·Arsenic

·Cadmium

·Mercury

Residual Solvents

Depending on the manufacturing process, relevant residual solvent limits may apply.

Microbiological Parameters

Depending on the specification:

·Total plate count

·Yeast and mold

·E. coli

·Salmonella

Official EU specifications for steviol glycosides include parameters such as total ash, loss on drying, residual solvents, arsenic, lead, cadmium,

mercury, and other purity criteria.

The important point is:

Do not assume that every COA needs exactly the same test panel.

Requirements can vary according to:

·Product type

·Manufacturing process

·Customer specification

·Target market

·Applicable regulations

The correct approach is to compare the COA against the relevant product specification and regulatory requirements.

7. Check Batch Number and Traceability

This is perhaps the simplest parameter to check - and one of the most important.

A professional COA should be connected to a specific batch.

Look for:

·Product name

·Batch / lot number

·Manufacturing date

·Expiry or retest information

·Test date

·Specification

·Actual test results

·Quality approval

Why?

Because a generic specification sheet tells you:

What the product is supposed to be.

A batch-specific COA tells you:

What this particular batch was actually tested as.

That difference is critical for quality management.

Specification vs. COA: Don't Confuse Them

This is a point worth emphasizing.

Product Specification

Defines:

What the product should meet.

COA

Shows:

What the tested batch actually achieved.

For example:

The specification establishes the acceptance criteria.

The COA provides the batch-specific result.

Both documents are important, but they serve different purposes.

A Practical Stevia COA Checklist

Before purchasing, ask your supplier:

Product Identity

☐ What exactly is the product?

☐ Is the stated purity Reb A, total steviol glycosides, GSG, Reb M, or another specification?

Glycoside Profile

☐ What are the major glycosides?

☐ Is a detailed glycoside profile available?

Analytical Method

☐ What method was used?

☐ Is the result reported on an as-is or dry basis?

Physical & Chemical Parameters

☐ What is the moisture / loss on drying?

☐ What are the ash and pH specifications where applicable?

Safety

☐ Are heavy metals controlled?

☐ Are relevant residual solvents controlled?

Microbiology

☐ Are microbiological parameters tested according to the applicable specification?

Traceability

☐ Does the COA correspond to a specific batch?

☐ Can the supplier provide supporting technical documents?

A Simple Example

Imagine you receive two COAs.

COA A

Stevia Extract

Purity: 95%

That's all the document tells you.

COA B

Rebaudioside A

Assay: 97.8%

Glycoside profile: Provided

Moisture: Provided

Heavy metals: Provided

Microbiology: Provided

Batch number: Provided

Analytical method: Provided

Which one gives you more confidence?

Obviously, the answer is COA B.

Not necessarily because the number is higher.

But because you have more information with which to evaluate the material.

The Biggest Mistake: Comparing Only the Purity Number

This is probably the most important takeaway from this article.

A buyer may compare:

Supplier A - 95%

Supplier B - 97%

Supplier C - 98%

and immediately assume:

98% must be the best product.

That conclusion may be wrong.

A professional comparison should consider:

Purity

·

Glycoside profile

·

Analytical method

·

Physical properties

·

Safety parameters

·

Application performance

·

Traceability

Only after looking at these factors can you make a meaningful comparison.

What Should a Professional Supplier Be Able to Provide?

For a serious food ingredient project, a supplier should be able to support customers with appropriate technical documentation, such as:

COA

Certificate of Analysis

TDS

Technical Data Sheet

SDS / MSDS

Safety Data Sheet

Product Specification

Detailed quality requirements

Regulatory Documentation

Depending on the target market and application

The exact documentation package will depend on the product and destination market.

TangBaobao Quality Approach

At TangBaobao, we believe transparency is an important part of ingredient quality.

For steviol glycosides, a reliable supply relationship should go beyond simply providing a price per kilogram.

Our approach focuses on:

Clear specifications

↓

Batch testing

↓

Quality control

↓

Traceability

↓

Technical documentation

↓

Application support

Whether the requirement is for RA, GSG, or RM, our goal is to help customers understand exactly what they are purchasing and how the ingredient fits their formulation requirements.

Final Takeaway

A COA is more than a piece of paperwork.

It is a window into:

·Product identity

·Composition

·Quality

·Safety

·Testing

·Traceability

When purchasing steviol glycosides, don't ask only:

"What is the purity?"

Ask:

"What exactly is this purity measuring, how was it measured, what is the glycoside profile, and can this result be traced back to a specific batch?"

That is the difference between simply buying an ingredient and professionally evaluating an ingredient.

References

[1] European Commission - EUR-Lex. Commission Regulation (EU) 2021/1156 of 13 July 2021. Amending the specifications for steviol glycosides and introducing provisions concerning rebaudioside M produced via enzyme modification. EUR-Lex - Commission Regulation (EU) 2021/1156

[2] FAO / JECFA. Combined Compendium of Food Additive Specifications - Steviol Glycosides. FAO/JECFA - Steviol Glycosides Specifications

[3] European Commission - Consolidated Food Additive Specifications. Commission Regulation (EU) No 231/2012 - Specifications for food additives. EUR-Lex - Consolidated EU Food Additive Specifications