NaturePreserve pH Adjustment and Stability in Formulations

Question

I have questions regarding the use of NaturePreserve in cosmetic formulations, specifically concerning pH adjustment and stability.

1. When mixing the water phase and adding NaturePreserve, should I wait approximately 1 day before measuring the pH for accuracy?
2. I understand that Gluconolactone gradually breaks down to maintain a low pH. If I add a base (like Triethanolamine), will it only temporarily increase the pH?
3. I previously formulated a 100g Natural Urea 5% cream using only 0.25g of Gluconolactone (from NaturePreserve). The pH was 5.5 immediately after mixing, dropped to 3.5 after 1 day, and stabilized around 4 after 3 days. Is this expected pH behavior?

MySkinRecipes Expert · Accepted Answer

NaturePreserve and pH Adjustment Based on the discussion, here are the key points regarding NaturePreserve and its effect on pH in cosmetic formulations: Effect on pH: NaturePreserve, containing gluconolactone, is acidic and will lower the pH of your formula. The extent of the change depends on the concentration used and other ingredients. When to Add: Adding NaturePreserve to the water phase early is recommended for easier pH measurement. Note that thickeners like Pro Polymer can also slightly influence pH. Gluconolactone Breakdown: Gluconolactone breaks down over time after dissolving, causing an initial pH drop before stabilizing. Accurate pH Measurement: For precision, wait approximately half a day to one day after adding NaturePreserve before measuring the final pH to allow the gluconolactone to fully react. pH Adjustment: If the formula is too acidic (below target pH), Triethanolamine is recommended for adjusting the pH upwards, as it offers more precise control than Sodium Hydroxide. Alternative Adjustment Strategy: For simpler production, especially in larger batches, consider reducing the NaturePreserve concentration (and potentially adding another preservative) if the pH is consistently too low. Stability Testing: Conduct stability tests (e.g., 1 month at 40°C) to monitor long-term pH changes and adjust the NaturePreserve ratio as needed to ensure stability over the product's shelf life (e.g., 2 years with pH below 7.0).