Autumn 2021 ZOOM Webinar Symposium

September 14 & 15, 2021

Principles and Practices in the Use of Surrogates in Process Evaluation

Surrogate Selection and Calibration

Two, 3 ½ Hour On-Line Technical Sessions

Symposium Chairs:    

  • Yuqian Lou, PepsiCo
  • Rick Falkenburg, Berner Food & Beverage

Tuesday, September 14, 2021, 11:00 am EDT

11:00   Introduction

11:10   FDA views on surrogate selection & calibration

            Nate Anderson, FDA

11:30   Historical background on surrogate development for low-acid aseptic filling system validation

            Wilfredo Ocasio, Eurofins Food Integrity & Innovation

Validation of aseptic fillers intended for the production of low-acid, shelf-stable products is a core requirement of the FDA’s low-acid canned food (LACF) regulations (21CFR113 and 108.35). Microbiological challenges of the aseptic zone and packaging material sterilization cycles are important components of the validation process. These challenges are often conducted at the production site using non-pathogenic surrogate organisms that mimic the resistance of the pertinent target pathogen. This presentation will provide a brief history of the use of such surrogates for the validation of low-acid aseptic fillers along with the approach we have used to qualify the surrogates as adequate for the intended technology.

For example, spores of the Geobacillus stearothermophilus with known D and z values were used for the validation of the earliest versions of low-acid aseptic fillers (i.e., Dole Canning Aseptic filler). Chemical sterilization of the aseptic zone surfaces and packaging material in form-fill-seal aseptic units required the identification and characterization of new surrogates in order to assess the efficacy of these cycles.

Starting in the 1970’s surrogates were investigated for validating the efficacy of sterilizing low-acid aseptic systems and associated packaging materials with hydrogen peroxide solutions. This required understanding the kinetics of destruction of the spores of Clostridium botulinum by this chemical sterilant. In the early 1980’s, our internal records show the evaluation and use of spores of various species of the genus Bacillus as surrogates of C. botulinum to validate the sterilization cycles of some of the earliest versions of low-acid, aseptic fillers introduced into the United States market. Yet the introduction of peracetic acid-(PAA) based sterilants required additional research that indicated that Bacillus cereus not C. botulinum was the most resistant pathogen to this novel application of PAA as a sterilant. This presentation will outline the approach used to find and characterize a surrogate for using in the validation of low-acid aseptic filler using PAA as a sterilant.

12:00   Surrogate calibration and ISO approach

            Guido Moruzzi, Consultant

The ISO 11138 family of standards sets the norms for biological indicators of sterilisation in the health care and medical device industry.

These standards set general rules (Part 1) and specific requirements for various sterilisation techniques: Ethylene Oxide, Moist Heat, Dry Heat and Steam + Formaldehyde. The typical techniques used for sterilisation of packaging materials and aseptic zones in aseptic packaging of food products are not normed.

However, several indications can be taken from the norms, especially from Part 1 General Rules and Part 7 Guidance for Selection, Use and Interpretation of Results.

The resistance of biological indicators vs. the specified sterilisation technique must be characterised and expressed as D-value. It follows that the inactivation kinetics of the biological indicator must be first-order log-linear. Resistance is a property of the biological indicator, i.e., of the test organism deposited on a suitable carrier, as the carrier itself may modify the resistance of the test organism.

Methods for resistance determination are described in appendixes of both Part 1 and Part 7. Resistance may be determined with two methods, namely Survivor Count and Fraction Negative. Additionally, the Survival/Kill technique may be used to verify an expected D-value, for instance, in the case of a known, previously tested spore crop.

In this presentation, we will describe and discuss the methods proposed by the ISO standards and their applicability to sterilisation with hydrogen peroxide, where test organisms typically show D-values of a few seconds at 35%, 70°C.

An alternative method to calculate D-value from fraction negative data is also mentioned, and the implications of the requirement of log-linear kinetics are discussed.

12:30   Break

12:40   Tetra approach to surrogate selection and application for filler biovalidation

            Martin Lappann, Kristina Eriksson, Fredrik Hansen, Tetra Pak

Sterilization techniques for surface sterilization of Aseptic Packaging Machines have to prove minimum log cycle count reductions (LCR) of the most resistant realistic pathogen, the so-called target microorganism. In case of the here discussed sterilization techniques liquid hydrogen peroxide, gaseous hydrogen peroxide, condensing hydrogen peroxide in combination with UV light, and e-Beam irradiation, Clostridium botulinum is the agreed target organism for surface sterilization in Aseptic Packaging of Low Acid Canned Food (LACF). Since target microorganisms of public health concern like C. botulinum cannot be applied in an inhouse test environment, appropriate non-pathogenic surrogate microorganisms used as test organisms need to be used as test organisms for validation or verification of sterilization processes. Proposed test organisms have to fulfil minimum selection criteria to demonstrate suitability as surrogate such as acceptable biosafety profile, sufficiently high resistance to the sterilization process, and first order inactivation kinetics. Here we disclose the Tetra Pak conceptual path for selection of test organisms. The scientific base for the suitability as surrogate for chosen test organisms is outlined here. For the sterilization techniques liquid hydrogen peroxide, gaseous hydrogen peroxide, condensing hydrogen peroxide plus UV light irradiation, and e-Beam irradiation we introduce our resistometers (test rigs) and a standard method for resistance determination. The application of state-of-the-art test rig equipment in combination with standard methods allows precise resistance determination and selection of individual test organism spore batches.

13:20   Surrogate spore calibration for low acid aseptic processes with hydrogen peroxide as the sterilant

            Yuqian Lou, PepsiCo

There are no published methods and criteria for calibration of surrogate spores that are to be used for biovalidation of low acid food aseptic systems. The presentation outlines an approach of calibrating spores for use in hydrogen peroxide-based sterilization of low acid aseptic systems; it is proposed based on a calibration practice that originated from NFPA, following the recommendations of the ISO standard. Some commonly used surrogates are also discussed in the presentation. Note: The views expressed are those of the author and do not necessarily reflect the position or policy of PepsiCo, Inc.

13:50   Break

14:00   Panel Discussion

14:30   Adjourn

Wednesday, September 15, 2021, 11:00 am EDT

Applications in Low Moisture Foods

11:00   Introduction

11:10   Development of surrogates for low water activity biovalidation: a tree nut case study

            Linda Harris, UC Davis

Twenty years ago, an outbreak of salmonellosis (Salmonella Enteritidis Phage Type 30) in Canada and the U.S. was linked to consumption of raw California almonds. This outbreak along with a second in 2004 (Salmonella Enteritidis Phage Type 9c), lead the almond industry, through the Almond Board of California (ABC), to develop federal U.S. Department of Agriculture Marketing Service regulations that required California almonds sold in North America to be treated with a process that achieved a minimum 4-log reduction in Salmonella. The final version of the regulation published March 31, 2007, required processors to have treatment plans in place by May 31, 2007, and mandatory compliance with the rule went into effect September 1, 2007. In the background, ABC developed an administrative infrastructure to support the new regulation including establishing a Technical Expert Review Panel and publishing guidance documents on the data that would be required for various types of process validation including the preparation, short-term storage, and use of the surrogate organism Enterococcus faecium NRRL 2354. Laboratory studies focused on validation of methods to inoculate and recover microorganisms from almonds and evaluation of the thermal resistance of candidate surrogates when compared with Salmonella Enteritidis PT 30. Over the 14 years since the regulation went into effect, ABC and others have funded studies that address the safety of E. faecium NRRL 2354, evaluate culture-preparation methods and thermal resistance changes during storage of almonds, assess the thermal tolerance of other Salmonella serovars and other pathogens such as Escherichia coli and Listeria monocytogenes and evaluate the applicability of E. faecium NRRL 2354 as a Salmonella surrogate for non-thermal processes. This case study will provide an overview of the data that support the use of E. faecium NRRL 2354 as a Salmonella surrogate for use in almonds along with a discussion of the practices that might influence the outcome of a study and some considerations for the future.

11:50   Use of Surrogates in Thermal Processes: Past and Present

            Lisa Lucore, Shearer’s Snacks

Three widely accepted approaches to validating thermal processes available information include mathematical models, experimental data, and/or published literature. The challenge for any of these approaches is qualifying the validity of the information, materials, or methods to the product of interest. The use of published validation studies seems to be favored for the relative simplicity of the approach, but availability of reputable and applicable published data for Low Moisture Foods (LMF) has been limited. The second Malt-O-Meal recall and FSMA closely following with a requirement for scientific defense of the safety of LMF thermal processes began to change this situation. There are more but still relatively few publications directly addressing thermal validation of LMF products, however there is a much larger quantity of publications evaluating surrogates. To reach a scientifically defensible position, most LMF validations using published literature will also require verification of the predicted results by in-situ testing using surrogate organisms. Selecting the surrogate and methods to proper harvesting, application to product, thermal processing in a real or comparable production line, and subsequent enumeration of surviving cells are the key variables of the thermal process validation plan. Examples of the considerations for each of these variables from past validations will be shared.


  • Looking back: Development of Low Moisture Foods (LMF) thermal validation processes
  • Where are we now: Defensible choices of surrogates
  • How to move forward: Applying published case studies to various thermal processes

12:20   Break

12:30   Baking process validation research: current status and future challenges

            Kantha Channaiah, University of Missouri

The baking industry plays a significant role in the US economy with 3,000 commercial bakeries and 6000 retail bakeries with a market value of >30 billion U.S. dollars per year. Similar to the other human food manufacturing facilities, bakeries subject to the Preventive Control requirements in 21 CFR § 117.160 must validate that the preventive controls implemented are consistently effective in delivering adequate lethality to significantly minimize or control the hazard such as Salmonella or other pathogen(s). Additionally, the validation should be appropriate to the nature of preventive control and its role in the facility’s food safety system. Since validation is critical to achieve finished product safety and to comply with preventive control rule, a series of baking validation studies were carried out. Salmonella was chosen as the main pathogen of concern due to its ability to survive in low moisture foods and environment. Some of the research objectives included: conducting product-specific process validation research for various bakery products, developing product-specific process lethality models, and helping bakeries to comply FDA’s validation requirement. A total of 13 product-pathogen specific validation research has been completed along with nine product-pathogen specific lethality models. The baking validation research help bakeries to scientifically manage pathogenic microorganism on the incoming raw ingredients and helps determine effective baking process parameters besides substantial savings to the bakeries by avoiding costly recalls due to foodborne illness outbreaks. However, due to a rapid change in formulations and processing methodologies, it is important to evaluate the effect of various factors such as water activity, air convections, presence of inclusions, relative humidity, salt, sugar, fat level etc. as these can affect the total process lethality. Independent product specific validation studies are highly recommended if there is a significant change in formulations, pathogen of concern and baking process parameters.

13:00   How to maintain low moisture thermal processes between validations

            Brian Farina, Deibel Labs

The maintenance and upkeep of a thermal processing system is a critical component of processor’s Food Safety Plan.  Within the low moisture food industry, thermal systems can vary considerably in type, design, and monitoring/verification capabilities.  The goal of this presentation is to provide a summary of recommendations and best practices for maintaining an effective thermal lethality process and avoiding “surprises” at validation time.  In addition to device calibration, temperature mapping is one such activity which we have found to be unfamiliar, or not fully utilized, by many of our clients.  We will also discuss changes to a thermal unit that may not seem significant but can impact the unit’s ability to deliver the expected thermal lethality.  Finally, knowing the best time or criteria for revalidating a process will also be discussed.

13:30   Break

13:40   Panel Discussion

14:20   Closing Remarks

14:30   Adjourn

Both sessions will begin at 11:00 am Eastern Daylight Time (this will be 8:00 am on the US West Coast and 5 pm in most of Europe) and be scheduled to last for 3 ½  hours. The registration fee of $175 will allow you to access both sessions.

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