Is microbial testing necessary for all products and raw materials?
One of the questions some people might ask is whether we need to check all products and raw materials in manufacturing. To determine whether we need to perform microbial testing on products or raw materials, we need to understand some parameters that may lead to microbial growth. We can refer to several guidelines related to this topic.
For example, in the cosmetic industry, ISO 29621 provides guidance on risk assessment and identification of microbiologically low-risk products. Low-risk products are described in the guideline as any “product whose environment denies microorganisms the physical and chemical requirements for growth and/or survival.” The following are some parameters for low microbiological risk products based on ISO 29621:
Water activity (aw) ≤ 0.75
pH ≤ 3 or ≥ 10
Alcohol content ≥ 20%
Production conditions, such as filling temperature > 65°C
Packaging, such as single-use products or products that cannot be opened
Raw materials that can create a hostile environment, such as polar organic solvents, oxidizing dyes, propellant gases, and aluminium chlorohydrate and related salts ≥ 25%
If our product or raw materials do not meet all of the criteria above, it means we need to perform a challenge test according to ISO 11930.
Besides ISO 29621 for cosmetic products, in the pharmaceutical industry, according to the Indonesian Food and Drug Authority (PerBPOM No. 9, 2025), it is clearly stated that microbiological risk assessment is required as a basis to determine whether routine microbial testing can be reduced or eliminated. It also states that microbial testing can be removed when the materials are not suitable for microbial growth. However, when the materials support microbial growth, we must follow a comprehensive risk assessment.
Therefore, whether we work with cosmetic or pharmaceutical products, microbiological risk assessment is essential. Both ISO 29621 and PerBPOM No. 9 (2025) highlight that factors supporting microbial growth are the key aspects that determine whether the risk is low or high.
In this context, we need to consider environmental factors that affect microbial growth. Factors such as temperature, water activity, and nutrient availability influence microbial growth. Temperature plays an important role, as different microorganisms grow best at different temperature ranges, such as psychrophiles (cold temperatures), mesophiles (moderate temperatures), thermophiles (high temperatures), and hyperthermophiles (extreme heat). Therefore, different microorganisms require different temperature control strategies.
In addition, water activity is a critical factor for microbial growth. Studies have shown that cosmetic products with high moisture content are more susceptible to microbial contamination. Microorganisms require available water for their growth, so reducing water activity below certain levels can help control microbial growth.
Furthermore, nutrient availability, such as carbon, nitrogen, phosphorus, and trace elements, is essential for microbial growth. Therefore, we need to ensure whether these nutrients are present in the product formulation.
Finally, microbial growth is also affected by pH levels and osmotic pressure. Microorganisms grow best within specific pH ranges, although some can survive in extreme acidic or alkaline conditions. Similarly, osmotic pressure, influenced by solute concentration, affects water availability and cell stability, which in turn impacts microbial growth.
Reference
Roy, S., Majumder, S., Deb, A., & Choudhury, L. (2023). Microbial contamination of cosmetics and the pharmaceutical products, and their preservation strategies: A comprehensive review. Novel Research in Microbiology Journal, 7(5), 2116-2137.
Porollo, M. (2023). The role of environmental influence from microbial growth dynamics. Applied Microbiology: Open Access, 9, 287. https://doi.org/10.35284/2471-9315.23.9.287
International Organization for Standardization. (2017). Cosmetics—Microbiology—Guidelines for the risk assessment and identification of microbiologically low-risk products (ISO 29621:2017).
PerBPOM No.9 2025