Understanding the Discoloration in Your Cream Formulation

The browning observed in your cream formulation, which contains Copper Peptide, Pep-Coll, Argireline, Caffeine, EGCG, Adenosine, and Phenoxyethanol, is most likely due to the interaction between Copper Peptide (GHK-Cu) and EGCG (Epigallocatechin Gallate).

Copper peptides contain copper ions, which are metal ions. EGCG, a potent antioxidant found in green tea extract, is a type of polyphenol. Polyphenols are prone to oxidation, and the presence of metal ions like copper can catalyze and accelerate this oxidation process. This oxidation often results in a change in color, typically turning brown or reddish-brown, over time.

While your formula's pH of 5.5 is within the recommended stability range for Copper Peptide (pH 4.5-7.4), this pH range primarily addresses the stability of the peptide itself, not necessarily its potential interactions with other ingredients like EGCG.

Regarding your consideration to switch from Phenoxyethanol to Mild Preserved Eco, Mild Preserved Eco is a suitable alternative preservative. Its INCI name is Ethylhexylglycerin, 1,3 Propanediol. It functions as a preservative blend and humectant and is not classified as a traditional preservative by the FDA, allowing for "preservative-free" claims. It is compatible with a pH range of 4-9, which works well with your formula's pH of 5.5.

However, switching to Mild Preserved Eco is unlikely to prevent the browning caused by the interaction between Copper Peptide and EGCG, as this reaction is primarily driven by the active ingredients themselves rather than the preservative.

To minimize or prevent this discoloration, you might consider:

• Reducing the concentration of either Copper Peptide or EGCG in the formula.
• Incorporating a chelating agent to bind the copper ions, although this could potentially impact the efficacy of the Copper Peptide.
• Packaging the product in opaque containers to protect it from light exposure, which can accelerate oxidation.
• Storing the finished product in a cool, dark environment.

Understanding the interactions between active ingredients is crucial for stable and effective formulations.