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.