As Dr. Acheson stated previously, manufacturers should, “…add a viable kill step that would not compromise the product, and look for other cost-effective ways to reduce the risk through supply chain and processing controls,” so a plan to reduce risk should combine process validations and verifications to ensure a process is in control and within acceptable deviations of the process calibration.
A dry surrogate can easily inoculate small and large quantities of food. The dried and ready-to-use surrogates are blended to create inoculation with flour. The blending can be a function of simply pouring the dry surrogate into the pre-conditioner (mixer) of an extruder, or distributed in thermal bags, or as a large volume inoculation of multiple tons of product. The thermal bags are an efficient method of distribution to confirm thermal penetrations by RF treatment in bulk capacity bags.
An in-plant validation project with surrogate microorganisms commonly includes three major steps and dry surrogates are no different. The first step is to define a validation strategy that is based upon the following.
- The level of inoculation for the surrogate organism, taking into account detection limits and background microflora of the tested product matrices.
- The inoculation method for the surrogate (liquid vs. dry vs. combined inoculation method).
- The product and in-plant process will dictate the distribution method for the surrogate. It may require a containment method with resistant bags. The dry surrogate enables bulk inoculation of large quantities that can be performed in a lab or at the plant.
- Transportation and storage guidelines.
- The number of validation trials to be performed (a standard industry practice is three validation trials).
- The placement and recovery of the surrogate in the process: number of samples to be tested, non-treated and control samples, required staff, etc.
- Target enumeration protocol (selective vs. non-selective vs. combination method, number of replicate enumerations, etc.).
The second step is to verify the resistance of the surrogate at lab scale, which is particularly important for data validity. A surrogate must demonstrate similar or greater thermal resistance when compared to the target pathogen to be considered effective. A food matrix can have significant effects on pathogen heat resistance during processing. The resistance data is more credible after developing:
- The number of surrogates to evaluate (usually one to three) and the choice of the surrogates to test;
- The inoculation methods and levels for the surrogate and the pathogen(s) to test (cocktail vs. single strain, dry vs. liquid form);
- The inactivation stress to be applied (dry heater apparatus, oil bath, lab oven, chemical bath, chemical spray, etc.);
- The processing parameters and exposure times to be evaluated and
- The number of assays (two or three in general) and replicate enumerations.
The third and last step consists of performing validation trials directly on the kill step within the in-plant processing equipment. The product matrices will be inoculated with the surrogate and then distributed within the in-plant processing equipment. Post-process samples will be collected and analyzed, which can determine the capacity of the kill step process to inactivate pathogens.
Dry surrogate technology is uniquely capable for use in in-plant process preventive control validations to create “gold-standard” data to validate the process, which is a pivotal benefit for food safety and regulatory compliance. Dry surrogates are great, but you still need to resist the urge to sneak a bite of raw cookie dough.
Umberson is business development director at Novolyze. Reach him at email@example.com. Roberts is vice president of business development at Novolyze. Reach her at firstname.lastname@example.org.