Preservative Challenge Testing for Dietary Supplements
Preservation of liquid dietary supplements is critical to product quality and long-term stability.
Currently, there is no organization-specific method that describes challenging preservatives within dietary supplements. The fundamentals of such testing, therefore, default to methods such as the USP <51> “Antimicrobial Effectiveness Test”, wherein a sample of the product is inoculated with a host of different microorganisms then incubated for a set amount of time. The product is then sampled in intervals to determine the microbial concentrations at each one.
Preservative effectiveness of dietary supplements is determined in a similar fashion to that of personal care products: A reduction in microbial concentration should be seen over time, and mold should not increase.
What microorganisms should be used for preservative testing of dietary supplements?
The standard microorganisms for a USP <51> test are Aspergillus brasiliensis, Candida albicans, Escherichia coli, Pseudomonas paraeruginosa, and Staphylococcus aureus. To challenge dietary supplements, we would inoculate samples with problematic foodborne pathogens such as Burkholderia cepacia, Salmonella enterica, and Listeria monocytogenes. Fundamentally, dietary supplements are foods. Thus, challenge with foodborne pathogens is appropriate and wise.
