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‘Kill step’ validation of low-moisture extrusion


In the USA, the Food and Drug Administration has had a zero tolerance policy for Salmonella since 2010, which is why various extrusion industries have experienced a dramatic increase in recalls over the past two years.

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									                               Digital Re-print -
                               May | June 2013
‘Kill step’ validation of low-moisture extrusion

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‘Kill step’
 validation of low-moisture
               by Will Henry, research &
       development, Extru-Tech Inc., USA

                                                                                                             Figure: 3 E525 extrusion system

   n the USA, the Food and Drug                   production scale Extru-Tech E525 extrusion
   Administration has had a zero tolerance        system. As a result, Extru-Tech now offers
   policy for Salmonella since 2010,              the industry’s first scientific validation study   Key considerations used in
which is why various extrusion industries         of a food/feed extrusion system that kills         the study
have experienced a dramatic increase in           Salmonella at levels higher than normally          For the development stage of this
recalls over the past two years.                  found in most facilities.                          process, key operational parameters
                                                     In an effort to target an industry with the     were analyzed to scientifically validate a
    In many of these recalls, Salmonella was      highest exposure, Extru-Tech chose to first        typical extruded pet food process.
found in the plant (commonly found in raw         address specific issues within the pet food
materials) and even though very few cases         industry by tailoring their validation protocol    Equipment scale - production
led to sickness, the manufacturer decided to      to an adult canine specification. However,         rates
recall all batches produced at that time. It’s    due to the equipment design duplicity, this        Impartial and internal studies have prov-
better to be safe than sorry, but these recalls   same architecture and protocol provides            en the agnostic relationship between
undermine consumer confidence, damage             credibility to multiple extrusion markets.         laboratory scale equipment and pro-
brands and impact the entire industry.               “Extru-tech is using actual equipment           duction scale equipment
    While every manufacturer strives for          that you would find in most pet food plants        Equipment configuration - barrel screw
products that are 100 percent pathogen            in a bio-hazard laboratory or a pilot plant,”      stack-up, preconditioner paddle con-
free, applicable and validated scientific stud-   says Dr Jim Marsden, regents distinguished         figuration
ies to support properly designed extrusion        professor, Kansas State University. “Raw           Impartial and internal studies have
food safety systems weren’t possible…until        materials can be inoculated with Salmonella        shown that even the slightest change in
now.                                              or other pathogens and the effect of the           equipment setup will impact the proc-
                                                  extrusion process can be exactly quantified.       ess’s pathogenic efficacy
Kill step validation                              This process is a breakthrough for the pet
    To mimic how products are contami-            food industry.”                                    Formulation
nated under real-world production facil-                                                             Impartial and internal studies provide
ity conditions, Extru-Tech built a BSL (Bio-      Production scale vs traditional                    excellent insight into the variations
Safety Level) 2 pilot plant outfitted with a      testing methods                                    inherent within individual ingredient
                                                                      Food/feed manufactur-          components and how they interact
                                                                   ers have relied on tradi-         differently within a processing environ-
                                                                   tional lab studies based on       ment (i.e. thermal energy efficiency,
                                                                   testing equipment ranging         water absorption, energy of gelatiniza-
                                                                   from beakers and pressure         tion)
                                                                   pots to table-top model
                                                                   extruders. Most testing           Product specification
                                                                   has been completed on a           Parameters such as: size, shape, den-
                                                                   lab table at very low pro-        sity, cell structure, moisture and water
                                                                   duction rates of 30 g to a        activity
                                                                   1 kg per hour - not exactly       Impartial and internal studies reflect that
                                                                   real world conditions.            specific changes in product character-
                                                                      Typically for a pilot          istics via process management, equip-
                                                                   scale extrusion lab, the          ment configuration or formulation, will
                                                                   Extru-Tech model E325             directly affect the efficiency of microbio-
     Figure 1: Collection of equipment architecture that           would be used. However,           logical control.
                represent models for existing validations          the smallest change, from
                                                                   the lab E325 (3.25 in

22 | may - June 2013                                                                                        Grain  &feed millinG technoloGy

                                                                       Creating a dry             introduced into the ingredient stream better
                                                Figure: 2 E925         inoculant test             represents how the pathogens are usually
                                                high capacity               A significant point   present within contaminated raw ingredients.
                                                extrusion               of discovery is how a          The obvious pathogen choice was a
                                                system (13 to           raw material is con-      3-serotype cocktail of Salmonella as it is the
                                                15 t/hr pet             taminated or inocu-       most opportunistic organism that is preva-
                                                food)                   lated in a factory.       lent in the pet food industry and the media.
                                                                        Various preemptive        The selected industry generic pet food for-
                                                                        trials, discovered that   mula was charged with a tailored inoculant
                                                                        many of the read-         that represents typical contamination events
                                                                        ily available and sci-    in the manufacturing process.
                                                                        entific methods of            Ultimately all three replications of the
                                                                        inoculation are not       challenge study resulted in a log reduction of
                                                                        truly representative      Salmonella that exceeded the 5-log reduc-
                                                                        of a typical contami-     tion requirement of a CCP allocation.
                                                                        nation event that our
                                                                        clients deal with on a    Validation 101
                                                                        daily basis.                  As any food safety auditor may tell you,
                                                                            For example, some     the ability to correlate the assignment of
    bore) to a production E525 (5.25 in       studies have developed thermal survivability        critical control points (CCPs) to scientifically
    bore), translates to a production rate    profiles (charts that show death of various         validated proof of their effectiveness in the
    of 200 to 600 pounds per hour for the     microbes against time or temperature).              control of targeted pathogens is ultimate
    E325 and upwards of 8,000 pounds per      However, these data sets were created with          confirmation of effectiveness.
    hour for the E525 (in terms of typical    the microbes suspended in a largely aqueous             “All food manufactures are required
    pet food). The process data translation   solution. If Salmonella is in a liquid, heat will   under the Food Safety Modernization Act
    is cumbersome at best and filled with     transfer quickly and kill it quickly. However,      (FSMA) to develop written food safety
    non-linearity.                            this is not a representation of what happens        plans,” says Dr Marsden. “For example, if
       With all this in consideration the     in a pet food plant and creates a false set of      Salmonella is a hazard that is reasonably likely
    BSL-2 pilot plant was outfitted with      operational parameters that do not control          to occur in the process or product, then a
    a E525 production scale extruder          Salmonella.                                         series of interventions are required and they
    system and the equipment was config-          For pet food, food, and feed manu-              must be scientifically proven.”
    ured for the production of an industry    facturers, Salmonella is usually introduced             Validation is the process of demonstrat-
    generic low-moisture dry-expanded         through dry ingredients. For this reason, we        ing that a food safety system (HACCP,
    pet food.                                 developed a dry inoculant. A dry inoculant          CCPs, CLs) as designed can adequately

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                                                                                                     Study parameters
                                                                                                     Possible paths for validation of a typical
                                                                                                     pet food process were reviewed in
                                                                                                     order of preference and viability:

                                                                                                     Pilot plant - most accepted and least risk
                                                                                                         Configure a pilot plant with
                                                                                                         representative production-scale
                                                                                                         equipment models and perform
                                                                                                         a tailored challenge study with
                                                                                                         specific formulations, equipment
                                                                                                         configuration, product specifications
                                                                                                         and targeted pathogens
                                                                                                         Pros - correlation becomes moot,
                                                                                                         no risk
               Figure 4: Summary data of extrusion validation for all three repetitions                  Cons – none
                                                                                                      In-plant surrogate
                                                                                                         Select non-pathogenic surrogate
                                                                                                         and inoculate actual production
                                                                                                         process flow
                                                                                                         Pros - matched equipment and
                                                                                                         process model
                                                                                                         Cons - lack of applicable
                                                                                                         (correlation) challenge study data
                                                                                                      In-plant pathogenic
                                                                                                         Inoculate actual production process
                                                                                                         flow with pathogenic microbe
                                                                                                         Pros - correlation becomes moot.
                                                                                                         Cons - risk of future events and
                                                                                                         liability thereof
                                                                                                      Laboratory validation
                                                                                                         Secure a BSL-2 laboratory to
                                                                                                         perform ‘bench-top validation
                                                                                                         Pros - specific pathogen, surrogate
                                                                                                         correlation, tailored formulation
                                                                                                         Cons - does not replicate
                                                                                                         equipment scale, configuration or
                                                                                                         the manufacturing process
                                                                                                      Scientific literature - least accepted
                       Figure 5: XX Extru-Tech Inc. pilot plant control system screenshot                and most risk
                                                                depicting CCP verification               Search for existing scientific
                                                                                                         data that best represents your
                                                                                                         manufacturing model
control (5-log reduction) the identified             are reduced or killed through the                   Pros - least cost
hazards to produce a safe product. As the            lethality conditions of the CCP.                    Cons - difficult to find a single
United States Department of Agriculture              “The best way to see how effective an               study that will be even minimally
indicates there are two distinct elements        intervention is against certain pathogens is            representative of a pet food
of validation:                                   to actually inoculate a food product with               extrusion process
  • The scientific justification or              Salmonella,” says Dr Marsden. “We then
    documented basis for the system              apply that intervention under conditions
    design requires scientific and technical     that ideally replicate a real-world food plant
    documentation that demonstrates              to measure the reductions associated with         eters that are required to deactivate
    the designed process can control the         that treatment. As a result, we know exactly      Salmonella in the extrusion process,” says
    identified hazard. The practical and         how effective an intervention is in controlling   Dr Marsden. “There are other production
    scientific demonstration must prove          specific pathogens.”                              steps that follow where Salmonella could
    the system can perform as expected.              Basing a food safety system on impractical    re-contaminate the product. Extru-tech is
    This consists of keeping records to          data is not safe! By selecting a sub-standard     looking at those additional steps to identify
    demonstrate the plan in operation            food safety model, you forfeit all leverage to    interventions that could be applied down-
    and that the HACCP plan achieves             mitigate the risk of a food safety event.         stream to prevent recontamination.”
  • Conducting multiple repetitions in a         Validating your extrusion food
    real-time processing environment using       safety system
    full- scale production equipment and            Until now, an extrusion kill step validation     More inforMation:
    actual production formulations that          has not been available in the food industry.         Tel: +1 785 284 4133
    have been inoculated with designated         Extru-Tech now offers scientific validation          Website:
    high levels of specific (non-man made)       focused on the extruded foods that exceed            Newsletter: http://eforms.kmpsgroup.
    microorganisms. The process also must        FSMA requirements.                                   com/wattpub/forms/extr_subscribe.htm
    prove that high levels of microorganisms        “Extru-tech is documenting the param-

24 | may - June 2013                                                                                        Grain &feed millinG technoloGy
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