A cleaning formulator substitutes a biosurfactant for an alcohol ethoxylate, runs a standard foam test, sees comparable numbers, and ships a batch that underperforms in the field. The bench test measured foam height and missed everything else.

This note is for formulators and buyers qualifying a biosurfactant for an existing product. It covers what a substitution test has to measure, which properties change first, and how to run a qualification that predicts field behaviour.

Replacing a synthetic surfactant is a qualification project, not a swap of one ingredient for another

An ethoxylate in a cleaning formula is doing several jobs at once: wetting, emulsifying, foaming and sometimes acting as a coupler.

A replacement that performs well on one of those jobs may fail on another, and the failure then appears in a different part of the product story than the one being tested.

Writing down the functions before testing keeps the project focused on performance rather than on a single headline number.

Wetting and emulsification are the two properties that decide most industrial outcomes

Dynamic surface tension determines how fast a solution wets a soiled surface, and it is not the same as the equilibrium value on a datasheet.

Emulsification decides whether an oil stays suspended long enough to be removed, and a weaker emulsifier leaves a film that customers notice.

Both properties can be measured on small samples, and both should be measured at the concentration and the temperature that the process actually runs at.

Foam is the property that breaks the most substitutions, and it breaks them in both directions

Some biosurfactants foam harder and drain more slowly, which is welcome in a hand dish product and unacceptable in a machine application.

Others foam far less, which suits industrial spray cleaning and completely ruins the customer expectation in a retail hand-dish formula.

Foam height alone does not describe this behaviour at all. Drain time and bubble structure matter just as much as the volume measured in the cylinder.

Electrolyte tolerance separates the grades quickly and cheaply

Many cleaning formulas carry builders and salts that push a surfactant out of solution.

Biosurfactants vary widely here, and a formula that is clear in deionised water can cloud or split once the builder is added.

A simple salt titration carried out at the working temperature tells you where the product actually sits before any expensive testing begins.

pH tolerance decides which formulations are even possible

Several biosurfactants are stable across a narrow band and hydrolyse outside it, which rules out alkaline cleaners and some acidic descalers.

The hydrolysis products are usually harmless but the surfactant activity is gone, and the formula fails slowly over shelf life rather than immediately.

Testing at the pH of the finished product, stored at elevated temperature for a few weeks, is the cheapest way to catch this before a launch.

Hard water performance is a commercial argument that has to be verified locally

Marketing material often cites hard water tolerance as the reason to switch, and the claim is usually true in principle.

Whether it holds at the water hardness in the target market is a separate question, and hardness varies enough within a country to matter.

Testing with the local water, or a synthetic version of it, avoids a claim that is true globally and false where the product sells.

Preservation and microbial limits need testing on the diluted product

A fermentation-derived surfactant is itself a nutrient, so the finished formula supports growth differently from a synthetic one.

A preservative system that passes a challenge test in the concentrate may fail once the product is diluted at the point of use.

Running the challenge test on the diluted form, at the temperature it is stored, is the only version that reflects what the customer receives.

The qualification needs a reference, not an absolute threshold

Comparing the new formula against the old one on the same soils and the same substrate is more informative than any pass mark.

Absolute thresholds exist for regulated claims, and they matter there. For a private-label reformulation the comparison is what the customer will judge.

Keeping a properly retained sample of the old formula, stored under the same conditions, is the single most useful piece of preparation for this work.

Scale and supply have to be checked before the formula is locked

Qualification on a kilogram of sample material says nothing about whether the supplier can deliver tonnes at a consistent assay.

Batch-to-batch variation in colour, solids and odour is normal in fermentation, and the specification has to allow for it explicitly.

Locking a formula to a specification the supplier cannot hold is a reliable way to create a launch problem, and the biosurfactant market is still young enough that this happens often.

Regulatory positioning depends on the claim being made, not only on the molecule

A biosurfactant sold on a biodegradability claim needs the test method behind that claim, because the recognised methods differ in what they measure.

Readily biodegradable under one protocol is a specific statement, and it does not automatically satisfy a labelling scheme in every market.

Checking the claim against the destination market before the artwork is printed avoids a repack, which is more expensive than the testing would have been.

Cost per unit of active is the comparison that survives negotiation

Price per kilogram is the number on the quotation, and it is the wrong number for a formulator.

What matters is the dose required to reach the performance target, multiplied by the price, which is why the CMC and the wetting data matter commercially.

A product at twice the price that needs half the dose is a neutral change, and that framing is what makes a switch defensible internally.

Documentation should follow the material, not the marketing folder

Ask for the technical data sheet, the safety data sheet, the assay method and the batch certificate as separate documents.

Where those documents disagree, the certificate is the one that describes the material in the drum, and the other two describe what was intended rather than what was made.

It is also worth asking which of those documents the supplier is willing to attach to a supply agreement, because the answer tells you how much confidence sits behind each of them.

The two commercial families behave differently enough that a test result does not transfer between them

Sophorolipids and rhamnolipids sit at different points on foam, pH and cost, and a formula qualified on one is not qualified on the other.

Suppliers sometimes offer both under a single brand, which makes it easy to assume the qualification carries across. It does not.

The microbial biosurfactants market has expanded fast enough that product families have blurred in marketing material well before they have blurred in the laboratory.

Running a short confirmation on the specific grade, rather than on the family, avoids discovering the difference during a production run.

FAQ: questions buyers ask

Can I substitute a biosurfactant one for one?

Almost never without reformulation. Foam, pH tolerance and electrolyte stability differ, and the formula has to be adjusted around the new molecule.

What should a qualification test include?

Dynamic wetting, emulsification on your soils, foam height and drain time, electrolyte tolerance, and a pH stability check at storage temperature.

Is a biodegradability claim enough for the label?

Only if the test method matches what the destination market's scheme requires. The claim and the certification are not the same thing.

Where does a biosurfactant usually fail first in the field?

In foam behaviour and in hard water, both of which pass a bench test run in deionised water at ambient temperature.

How do I compare two suppliers fairly?

On cost per unit of active at equal performance, not on price per kilogram, and on the batch variation each will commit to in writing.