Dry foods—such as pistachios, spices, cereals, and milk powders—may appear low risk due to their lack of moisture. But in reality, they can harbor dangerous pathogens like Salmonella, Listeria monocytogenes, and E. coli O157:H7 that can survive for long periods in dry environments (1,2). These organisms don’t need water to persist—and some, like Salmonella, can become more heat-resistant when suspended in low-moisture, high-fat food matrices (3).
Because pathogens may not be evenly distributed or easily detected, visual inspection and routine testing aren’t enough. Scientific validation of the thermal process—your kill step—is the only way to confirm that these organisms are reliably eliminated from every batch (4).
Under the FDA’s Food Safety Modernization Act (FSMA) and international standards like ISO 22000, food manufacturers must provide documented proof that their process consistently achieves the required microbial log reduction—typically 5-log or greater (5,6). But dry food processing can involve hidden risks: airflow imbalances, product moisture variation, cold spots in ovens, or high-throughput loadings can all compromise lethality (7). If the coldest zone or moistest product section doesn’t get enough heat for long enough, dangerous microbes may survive.
That’s where CREM Co Labs supports processors.
We specialize in validating microbial kill steps for dry food facilities using a structured, science-based approach. Our services include:
- Temperature Mapping: We identify thermal variation using high-accuracy sensors logged every 5 seconds.
- Product Residence Time Studies: We determine how long product remains in the kill zone and whether this satisfies process control criteria.
- Moisture and Water Activity Profiling: Since water activity affects heat resistance, we monitor these values at critical control points.
- Thermal Death Time (TDT) Analysis:
In our ISO/IEC 17025-accredited laboratory, CREM Co Labs conducts Thermal Death Time (TDT) studies to characterize how heat affects both target pathogens and surrogate organisms in the actual food matrix. We determine D-values (the time required at a specific temperature to achieve a 1-log reduction) and z-values (the temperature change needed to reduce the D-value by tenfold).
Critically, we use this data to compare the heat resistance of the selected surrogate to the target pathogen—typically Salmonella, Listeria monocytogenes, or E. coli O157:H7—under conditions relevant to your product (e.g. low-moisture, high-fat, or particulate form). This ensures that the surrogate is equal to or more resistant than the pathogen of concern. If it’s not, we adjust the surrogate or select another strain until it meets the required conservativeness.
This side-by-side comparison provides the scientific basis to justify that if your process inactivates the surrogate, it would also be effective against the pathogen—fulfilling regulatory and industry validation expectations.
- Surrogate-Based Microbiological Validation:
Once the surrogate’s resistance is confirmed through TDT studies, we proceed with in-plant validation trials using that surrogate. We inoculate the product (e.g., nuts, powders, or flakes) with a high concentration of the surrogate organism—commonly Enterococcus faecium NRRL B-2354, Pantoea agglomerans SPS2F1, or another scientifically justified strain (8).
The product is then processed on your actual line, under defined worst-case operating conditions (e.g. lowest validated temperature, fastest belt speed, or heaviest load). We collect and analyze pre-process, post-process, and control samples to determine the log reduction achieved.
If the target log reduction (e.g., ≥5-log for Salmonella) is not met, we work with your team to adjust the process—such as increasing time, temperature, or modifying airflow or load conditions—then retest until validation is successful.
This step proves, with real-world evidence, that your existing process does or does not deliver the required lethality. Once confirmed, we provide you with a complete validation report and help integrate those findings into your food safety plan.Together, these tools form a robust validation package aligned with regulatory expectations and industry best practices. With CREM Co Labs, processors gain confidence that their dry food process is not only compliant—but scientifically proven to protect public health.
References
- Beuchat LR, Komitopoulou E, Beckers H, Betts RP, Bourdichon F, Fanning S, et al. Low–Water Activity Foods: Increased Concern as Vehicles of Foodborne Pathogens. J Food Prot. 2013;76(1):150–72.
- Podolak R, Enache E, Stone W, Black DG, Elliott PH. Sources and risk factors for contamination, survival, persistence, and heat resistance of Salmonella in low-moisture foods. J Food Prot. 2010;73(10):1919–36.
- Blessington T, Theofel CG, Harris LJ. A dry-inoculation method for nut kernels. J Vis Exp. 2012;(66):e4160.
- Scott VN, Stevenson KE, Bernard DT, Gombas K, Sveum WH, Lachance PA. Guidelines for Conducting Lethality Validation Studies. J Food Prot. 2005;68(4):799–811.
- US FDA. Current Good Manufacturing Practice, Hazard Analysis, and Risk-Based Preventive Controls for Human Food; Final Rule. Fed Regist. 2015;80(180):55907–978.
- International Organization for Standardization. ISO 22000:2018. Food safety management systems – Requirements for any organization in the food chain. Geneva: ISO; 2018.
- Anderson DG, Lucore LA. Validating the reduction of Salmonella and other pathogens in heat processed low-moisture foods – Part 9: Validating the efficacy of the pasteurization process. PMMI OpX Leadership Network; 2012.
- Almond Board of California. Guidelines for Process Validation Using Enterococcus faecium NRRL B-2354. Modesto (CA): ABC; 2007.