Many of us have had to resist the urge to lick the bowl of the brownie mix or sneak a bite of cookie dough but many don’t resist the urge. The growth of ready-to-eat (RTE) flour can be traced to multiple food safety recalls, most recently in 2016, when the FDA investigated a multistate outbreak of Shiga toxin-producing E. coli infections linked to large domestic producer of flour. The impetus for these recalls stems from consumers consuming a not-RTE product (flour) prior to the kill step. After months of extensive testing, the pathogens E. coli O121 and E. coli 026 were detected in laboratory samples.
The risk of foodborne pathogens is increasing in grain products. U.S. wheat production is concentrated in the Midwest where livestock and poultry operations are also important to the agricultural economy. Farms and wild animals serve as a reservoir for these pathogens and with such close proximity, Salmonella or E. coli can be introduced into wheat fields and thus into wheat operations.
In his recent newsletter article, David Acheson, MD, founder and CEO of The Acheson Group, he noted that, “Flour has never been considered to be a ready-to-eat food. It is not treated as such in the field, in production, or at the consumer’s home. But with the regular flow of recalls caused by consumer consumption of raw flour, that may be about to change.” Dr. Acheson adds, “Will this impact regulation? Very likely. Eventually. But at the speed that regulation flows, I would recommend that, for both consumer and brand protection, any company selling a raw product to consumers take steps to determine if it is cost effective to 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.”
The grain products industry is adapting to environmental and consumer behavior induced risk. With a series of food illness outbreaks associated with low-water activity foods, the long-held belief that low-moisture foods are not a food safety risk is no longer valid in today’s world. The need to protect consumers and the corporate brand from the increasing risk has created a need to treat flour with a process that applies a kill step as a preventive control for foodborne pathogens like Salmonella or E. coli.
Treated Flour and Pregelatinized Flour
Treated flour is the result of heat, stress, and shear to reduce the risk of foodborne pathogens. Treated flour is used primarily as a RTE ingredient in products containing flour that might be consumed prior to cooking, such as cookie dough, ice-cream additives, mixes, seasoning blends, etc.
Pregelatinized flour serves a nutritional and process efficiency requirement that is also the result of heat, stress, and shear but not categorically enough to be considered a RTE product. The heat, stress, and shear required to create pregelatinized flours is very specific to break down the starch molecules with water and heat.
Pregelatinized flours perform well in cold water applications, thus enabling quicker mixing methods and they can gel without high heat. Pregelatinized flours can improve dough performance, increase viscosity, and suspend ingredients and are used in prepared and frozen products, sauces, many food preparations, baby foods, yeast products, ice cream, etc.
Treating Flour with Thermal Stress
Extrusion and radio frequency (RF) are examples of two processes used to further treat flour and provide a RTE ingredient.
By nature, extrusion is a continuous process where a food material is forced to flow through a die by a combination of mixing, shear force, and/or heat. A versatile technology with origins in the plastic industry, extrusion is a short-term, high-temperature process, used in a wide variety of products including flour, cereals, snacks, pasta, pet food, and livestock feed. When flour is heated by barrel heat, internal friction, and plastic flows of the product, (if validated) this process can be a preventive control step.
With the Food Safety Modernization Act (FSMA), there is an unquenched desire for more diverse forms of pasteurization, and RF heat treatment is a growing method of pasteurization for dry food products. Recent advancements in RF have alleviated many of the hurdles associated with non-uniform heating of products. Current designs allow for deep penetration of heat and uniform heating to ensure food safety.
In RF heating, a generator creates an alternating electric field between two electrodes. RF waves penetrate the food product and create heat energy by either orientation polarization, where the electrodes cause the water molecules in the product to continuously reorient themselves to face the opposite electrode or by ionic conductivity, where hydrated ions move according to the electric field. In both cases, heat energy results in the rapid heating of the product. RF is a good candidate for either a bulk or bagged product.
Validating a Heat Treatment/Kill-Step
FSMA Preventive Controls mandate that only process preventive controls must be validated; allergen, sanitation, recall, and supplier controls do not have to be validated. FSMA recognizes five approaches to validate a process preventive control measure. These approaches include: 1) reference to scientific or technical literature, previous validation studies, or historical knowledge of the performance of the control measures; 2) scientifically valid experimental data; 3) collection of data during operating conditions of food production; 4) mathematical modeling; and 5) surveys.
As a company evaluates these approaches, it may soon discover scientific and technical information is not available or is insufficient to support that the preventive control controls the hazard. The next step will be for the facility to conduct controlled scientific studies to establish that a preventive control measure is adequate to control the hazard.
While laboratory challenge studies are one way to conduct scientific studies, they can be fraught with inherent errors, the foremost being food processes are difficult to scale down to laboratory scale. Performing an in-plant, preventive control validation study is a gold standard approach to validation. What better way to validate a preventive control than with using the actual product and process.
In order to safely perform in-plant validation work, using surrogates is ideal. An appropriate surrogate is not a pathogen. It has a similar or greater thermal relationship when compared to the pathogen(s) of pertinence, it will not establish itself as a spoilage organism in the plant, it is easily killed during routine sanitation, and it is easy to detect and enumerate.
With the advent of dry surrogate technology, a smarter food safety tool has emerged for in-plant preventive control validation of low-water activity foods, including validation of hurdle technology or flour processing steps. Dry surrogate inoculation leads to minimal intrinsic property changes. With little to no intrinsic property changes, flour inoculated with a dry, ready-to-use surrogate can be used immediately after inoculation without a lengthy time period to re-equilibrate to original %moisture or Aw. Inoculation with a dry surrogate is homogenous and eliminates product clumping seen when inoculating a dry powder with a liquid surrogate. The ability to produce large, stabilized volumes of dry surrogate means that large volumes of food product can be inoculated. There are times when thermal bags, which are product inoculated with surrogate and placed in thermally-resistant bags, are not appropriate for the process. Obviously thermal bags will not fit through an extrusion process, they often won’t travel at the same speed as free-flowing product in a screw process or thermal bags may not experience the same thermal conditions as free-flowing product. With commercial production, high surrogate concentrations are also realized. While validation will not be performed at high concentrations, it does allow for inoculation of product with high background microflora with the ability to still evaluate for a 5-log lethality. The shelf life of dry surrogate has been evaluated to be at least three months when stored under refrigeration.
Validating Extrusion and RF
The advent of the new treated flours for better nutrition or commercial cooking is inherently tied to flour treatment for microbial content. Treated flour has a tight processing window regarding microbial lethality and nutrition modification of the grain by-product. The tight processing window for treated flour as well as consumer and brand liabilities require companies to fervently reduce risk with gold standard validations and periodic verification trials to insure calibration of the process.
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 firstname.lastname@example.org. Roberts is vice president of business development at Novolyze. Reach her at email@example.com.