20 Jan Challenge Studies for Process Authority Letters in Cold Chain Production
Cold chain products are increasingly popular in today’s food and beverage market, from refrigerated beverages and sauces to functional foods requiring temperature control. While cold storage reduces microbial risk, it does not replace the need for a Process Authority (PA) letter.
For many cold chain products, a challenge study is required to validate product safety and support PA approval.
This article explains what a challenge study is, when it’s required, and how it supports process authority letters for cold chain production.
What Is a Process Authority Letter?
A Process Authority Letter is a scientific validation issued by a qualified process authority confirming that a product and its manufacturing process are safe.
PA letters are commonly required for:
- Acidified foods
- Refrigerated and cold chain products
- Products sold through co-packers
- Retail and foodservice distribution
What Is a Challenge Study?
A challenge study intentionally introduces specific microorganisms into a product to evaluate whether the formulation and storage conditions prevent growth or survival.
For cold chain products, challenge studies help answer critical questions:
- Can pathogens grow if temperature control is compromised?
- Does the formulation inhibit microbial growth?
- Is refrigeration alone sufficient for safety?
When Is a Challenge Study Required?
A challenge study may be required when:
- pH and water activity alone do not clearly define product safety
- The product relies on refrigeration as a control
- The formulation contains borderline pH or preservative systems
- The PA cannot confidently group products into existing families
Cold chain products often fall into regulatory gray areas, making challenge studies a key risk-reduction tool.
Common Microorganisms Used in Challenge Studies
Depending on product type, studies may include:
- Listeria monocytogenes
- Salmonella spp.
- E. coli O157:H7
- Spoilage organisms (yeast and mold)
These organisms are selected based on product risk profile and intended storage conditions.
What a Cold Chain Challenge Study Evaluates
1. Formulation Safety
- pH stability over time
- Preservative effectiveness
- Ingredient interactions
2. Temperature Abuse Scenarios
- Short-term refrigeration failure
- Distribution and handling risks
- Worst-case consumer storage conditions
3. Shelf Life Validation
- Microbial growth trends
- Safe use-by dates
- Support for refrigerated shelf life claims
How Challenge Studies Support PA Letters
A completed challenge study provides data that allows a Process Authority to:
- Approve or modify processing parameters
- Validate cold chain dependency
- Define product families appropriately
- Reduce regulatory and co-packer risk
Without this data, PA approval may be delayed or denied.
Why Challenge Studies Matter for Co-Packers
Most co-packers will not accept cold chain products without:
- A valid PA letter
- Supporting challenge study data
- Clear operational boundaries
Challenge studies protect not only your brand, but also the co-packer’s food safety program.
Partnering With the Right Lab
Not all labs are equipped to run challenge studies for cold chain products. A qualified lab should:
- Design studies aligned with PA expectations
- Coordinate with your Process Authority
- Provide defensible, regulator-ready data
United Food Labs supports cold chain challenge studies and collaborates directly with Process Authorities to streamline approvals.
Cold chain production reduces risk—but it does not eliminate it. Challenge studies are often the missing link between product development and Process Authority approval.
If your product relies on refrigeration for safety, a properly designed challenge study may be the key to launching faster, safer, and with fewer regulatory obstacles.