From Labor-Intensive Methods to Real-Time Microbial Monitoring
Challenge testing is a cornerstone of product safety across cosmetics, pharmaceuticals, and food. Traditional methods rely on inoculating products with microorganisms and monitoring survival over time through repeated sampling, dilution, and plating, or by measuring optical density. While widely accepted, these workflows are labor-intensive, time-consuming, and dependent on indirect readouts of microbial growth.
For opaque or complex formulations such as creams, lotions, emulsions, or food matrices, traditional measurements become even more challenging. Turbidity cannot be used, plating becomes cumbersome, and large volumes of media, agar plates, and manual handling are required across multiple time points.
The Symcel calScreener® and calScreener+ simplifies challenge testing by directly measuring the metabolic activity of microorganisms within the product. It enables continuous, real-time monitoring of microbial growth or inhibition—without the need for repeated plating, visual inspection, or sample disruption.
CHALLENGE TESTING WITH BIOCALORIMETRY
Isothermal microcalorimetry with the calScreener provides a direct measurement of metabolic heat produced by viable microorganisms in a formulation. Instead of relying on colony formation as a proxy for growth, the system continuously tracks microbial metabolism. If a preservative is effective, metabolic activity remains flat or declines. If growth occurs, it is detected immediately as an increase in heat flow and automatically reported. This enables a fundamentally simpler and more informative workflow:
- Monitor microbial activity continuously instead of sampling at discrete time points
- Test opaque and complex formulations directly without modification
- Detect early metabolic activity long before visible growth appears
- Evaluate preservative efficacy under realistic conditions
REDUCING COST, TIME AND LABOR IN CHALLENGE TESTING
Traditional challenge testing scales poorly. Each formulation, concentration, and time point requires new plates, dilutions, and repeated manual handling. A single study can quickly expand into hundreds of agar plates, liters of media, and many hours of technician time.
With the calScreener, up to 32 formulations or concentrations can be tested in parallel in a single run. What would traditionally require hundreds of plates and repeated daily interventions is reduced to a simple setup with automated monitoring.
Compared to conventional workflows, hands-on time can be reduced to a fraction of traditional assays. This translates into lower labor costs, reduced consumable use, and faster time to results.
FROM INDIRECT ENDPOINTS TO CONTINUOUS INSIGHT
Challenge testing has always asked a simple question: Will microorganisms grow in this product? Traditional methods answer this indirectly by waiting for colonies to appear. Biocalorimetry answers it directly by measuring metabolic activity in real time.
This shift enables earlier detection of failure, improved understanding of microbial behavior, and more confident decision-making during formulation development. It also reduces the risk of overlooking metabolically active cells that do not form colonies under standard conditions. The result is a more sensitive, more informative and more efficient approach to challenge testing.
