English EN
What causes colour drift and off-notes in peptide-fortified products?
Beyond Biopharma | Plant Protein Peptide FAQ
Short answer: Colour drift and off-notes in peptide-fortified products come mainly from the Maillard reaction between peptides and reducing sugars, from oxidation of residual lipids, and from moisture and oxygen migrating through the package. These are slow, cumulative changes, which is why they usually appear during storage rather than immediately after production.
The Maillard pathway
Peptides carry free amino groups, and those groups react with the carbonyl group of reducing sugars such as glucose, fructose, lactose and maltose. The reaction needs no enzyme, only time and the right conditions, and it accelerates with heat, with higher pH, and at intermediate water activity where reactants can still move. Its early stages are invisible; later stages produce the yellow-brown pigments and the malty, cooked, caramel or stale notes that consumers notice. Because the same reaction consumes lysine, it also reduces nutritional quality, which is why colour and nutrition drift tend to be reported together in accelerated storage studies.
Oxidation and other routes
Lipid oxidation is the other main driver. Any residual fat in the protein ingredient, or an oil phase in the finished product, can oxidize into aldehydes and other volatile compounds that read as cardboard, rancid or painty. Trace metals such as iron and copper catalyze that reaction, as do light and heat, and the peptides themselves can supply the free amino groups that react with oxidation products to form additional browning. Where the plant material retains active enzymes, enzymatic browning can add to the picture, and packaging that lets oxygen or moisture through gives all of these routes more room to work.
Symptom to cause
| Symptom | Likely cause | Control |
|---|---|---|
| Powder darkens over months | Maillard reaction with residual reducing sugars | Lower water activity, keep cool, limit reducing sugars in the blend |
| Stale, cardboard or rancid notes | Lipid oxidation, often metal catalyzed | Antioxidant strategy, oxygen barrier, control trace metals |
| Surface yellowing on a tablet or bar | Localized moisture gain and reaction at the surface | Moisture barrier packaging, control humidity in the packing room |
| Colour change after heat treatment | Thermal Maillard advance during processing | Reduce heat load and pH, remove reducing sugars from the base |
Controls worth testing first
- Review every sugar source in the formula, including fruit powders, flavor carriers and maltodextrins, for its reducing sugar content.
- Keep water activity low in dry products and controlled in intermediate-moisture ones, since the reaction rate peaks in the middle of the range.
- Use packaging with a real moisture and oxygen barrier, and confirm the seal integrity rather than relying on the film alone.
- Add a suitable antioxidant and consider chelating trace metals, then verify the effect by measurement rather than by assumption.
- Test the finished product in its final pack under accelerated and ambient conditions, and measure colour instrumentally alongside a trained sensory panel.
Related reading
For more detail, see whether peptides survive UHT and retort processing, how peptide powder should be stored to avoid caking and how bitterness is prevented.
