Calculating Preservative Amount and Shelf Life for Cream

To calculate the amount of preservative needed for your cream formulation, you can use the recommended usage rate as a percentage of the total weight of your product.

Calculation Example (100g Cream with 1% Phenoxyethanol)

If you are making 100g of cream and the recommended usage rate for the preservative, such as Phenoxyethanol (Extra Pure), is 1%, the amount to add is calculated as follows:

Amount of preservative = Total weight of cream * Percentage usage rate
Amount of preservative = 100g * 1%
Amount of preservative = 100g * (1 / 100)
Amount of preservative = 1g

So, you would add 1g of Phenoxyethanol (Extra Pure) to your 100g cream formulation.

Shelf Life

The shelf life of your cream depends on several factors, including the type and concentration of preservative used, the cleanliness of your manufacturing process, the initial microbial load of your ingredients, and the packaging.

Based on the information for Phenoxyethanol (Extra Pure) at a 1% concentration, and assuming a clean manufacturing process with low initial microbial contamination, the preservative can effectively control microbial growth for a significant period. Generally, the preservative itself can remain effective for 3-5 years before degrading. However, other ingredients in your cream might degrade or lose efficacy before the preservative does.

It's important to note that Phenoxyethanol (Extra Pure) is primarily effective against bacteria and less so against fungi. For broad-spectrum protection against both bacteria and fungi, you might consider using a broad-spectrum preservative like Phenoxyethanol SA (eq. Optiphen Plus) or combining Phenoxyethanol (Extra Pure) with another preservative that is effective against fungi.

To determine the actual shelf life of your specific formulation, especially if you plan to sell the product, it is highly recommended to perform a microbial challenge test. This test evaluates the effectiveness of the preservative system in your final product against various microorganisms over time.