Measurements of the internal temperatures of products as they bake provide the input for AIB’s kill step calculator.

Prevention requires proof. That mantra defines a fundamental aspect of regulations under the Food Safety Modernization Act (FSMA). And it demands something new of bakers, indeed, of all food manufacturers: validation that their preventive controls actually work to keep pathogens of concern out of food products.

Bakers have a very safe record for production of shelf-stable foods. But pathogens such as Salmonella spp. can be introduced via ingredients like eggs, milk products, flour, milk chocolate, coconut, peanut butter, fruit and spices. The assumption has always been that oven temperatures of 200°F and above will kill any harmful microorganisms.

But how can the baker prove that to the satisfaction of the Food and Drug Administration (FDA) inspector? AIB International found a way to do just that, and it now offers its Kill Step Validation Calculator to anyone who needs it. Bakers attending IBIE can learn about the calculator at AIB’s presentation, “Kill Step Validation of the Baking Process for FSMA,” on Sunday, Oct. 9, at 8:30 a.m.

“The intention was to prove for the first time that the oven’s heat really does perform the kill step,” said Brian Strouts, AIB’s vice-president, baking and technical services.

New problem, new research

AIB started, quite literally, from scratch. “We had to establish the foundational research. There was zero out there,” Mr. Strouts explained.

FSMA differs from previous food safety regulatory approaches. “The switch to ‘preventive’ controls is to make sure that the preventive controls, when properly implemented, will effectively control the hazards that are reasonably likely to occur,” said Lakshmikantha (Kantha) Channaiah, PhD, AIB’s director of microbiology. “This approach assures FDA that everything in the kill-step process is aimed at controlling the micro hazards that are reasonably likely to occur. That’s why the regulations require validation, to make sure.

“The rules clearly state the need for validating a kill step in the food manufacturing process,” he continued. Obviously, it’s the oven, but the industry lacked scientific proof of this. “We asked ourselves, what would be considered essential proof? And we decided to get into this matter,” he added.

The American Bakers Association (ABA), through its Food Technical Regulatory Affairs Committee, got involved, too. “AIB International’s kill step protocol is closely attached to ABA’s efforts,” Mr. Strouts noted.

Led by Dr. Channaiah, the AIB team tapped the expertise of microbiologists at two universities, an emeritus statistician and a Level 2 Biosafety lab to pull together the research that would prove the theory that the oven could provide the FSMA-mandated kill step.

A data logger’s thermocouple probes are inserted into hamburger buns to collect data.

Killing harmful microbes

Microbial kinetics research provided the starting point with basic facts about temperature and microbial death rates. Different microorganisms, even different strains of the same microbe, will vary in the amount of heat it takes to kill them. In general, however, this starts to happen around 160 to 170°F. Buns bake in 425°F ovens.

“In the real world, baking usually proceeds to an internal temperature of 200°F, the temperature necessary to set the crumb structure,” Mr. Strouts explained.

Microbial destruction is measured by x-log reduction in colony-forming units (CFU), in which x represents the decrease in numbers at a logarithmic rate. A 5-log reduction means lowering CFU by 100,000 fold. “We noticed that FDA has used a 5-log reduction threshold in other industries,” Mr. Strouts said.

Choosing hamburger buns as the first model, researchers inoculated flour with different pathogens to achieve 6-log to 7-log CFU per g. It was stored for up to two days at ambient temperature before being mixed as bun dough. The normal steps of fermentation, dividing, makeup, proofing and baking followed.

To measure the internal temperature, researchers turned to data loggers, thermal recording instruments that bakers use to look at heat flow within their ovens. After baking, the finished buns were checked for pathogen content, seeking a minimum of 5-log reduction.

“We showed we killed everything in nine minutes, long before the normal 13-minute bake time ended,” Mr. Strouts said. “And there’s a built-in safety factor: If you under-bake the bun at less than the kill time, it is simply not sellable.”

The team then turned to statistical principles to develop a microbial kinetics-based interactive model — an Excel spreadsheet known as the Baking Process Kill Step Calculator. The baker gathers oven data on time and temperature during the baking process. This information drops into the spreadsheet. The calculator generates the lethality curve, which validates the kill step.

The study proved to be a first of its kind and was published in the April issue of Journal of Food Protection. AIB also presented it to the regulators. “Overall, FDA liked the kill step validation model,” Mr. Strouts reported. “We were told that we were the first industry group to come to FDA to explain what it was doing with kill step validation. It was a very positive meeting.”

More products covered

AIB started with hamburger buns and has since posted calculators for whole wheat bread, cake muffins, and crisp and soft cookies on its website, Next up are nut muffins, yeast-raised donuts and tortillas. These should be added in 2017.

As of this spring, AIB reported approximately 1,700 website views of the calculators, with more than 800 active users downloading them. “We anticipate that as new products calculators are released, this number will continue to rise,” observed Melissa Kirkwood, AIB’s media relations coordinator.

Each new calculator involves a different matrix of ingredients and processing conditions. That means a separate study is required, according to Dr. Channaiah. “There will be different data based on the unique aspects of each product type,” he said. For example, higher amounts of fat or sugar may make Salmonella more resistant to heat.

And then there are the not-so-simple physical challenges. The donut calculator, now in progress, offered the researchers an interesting problem. “The internal temperature is what is important,” Dr. Channaiah said. “But frying of donuts requires that they are flipped halfway through the process.”

Maintaining proper contact with the inside of the donut proved to be too difficult for hard-wired thermocouples. “But we found a new technology,” Dr. Channaiah explained. “It’s a button-like sensor about the size of a 25¢ piece. You put it right into the product.

“Each product type differs,” he added, “and we try to match the sensing technology to the product. We used these buttons first for fried items and will be using them in future studies.”

AIB managers advise that the calculator provides an estimate based on the individual bakery’s data. It can be used to validate the kill step process with the FDA inspector. “But proper use of the calculator requires that all the other preventative controls be in place to make sure the product remains pathogen-free after baking,” Mr. Strouts cautioned.

Microbiological tests determine the presence of pathogens.

Putting it to work

Since announcement of the bun calculator this past fall, a good number of bakeries have actually tested it. “We think the model is robust enough to handle a variety of conditions,” Mr. Strouts said. “The lab work was done with a home-style oven, and the calculator has been used with spiral, rack and tunnel ovens. When working with your own oven, you need to look at the worst-case scenario. In other words, you need to find the cool spot and run the tests there.”

Working the calculator is deliberately simple. “All the baker has to do is select time and temperature from the calibrated temperature data logger and paste them into the kill-step calculator, which automatically determines the total process lethality (e.g., 5 log) for Salmonella,” Dr. Channaiah said. “We had to make the method scientifically valid for the regulators and practical for the baker.”

The results are a graph of internal temperature vs. time and a process lethality curve that qualifies as documentation of kill step validation, as FSMA regulations require. “Any bakery can use this,” Dr. Channaiah said. “This is the proof, the document, required to validate the process.”

Earlier this year, AIB sponsored a webinar introducing its kill step calculator. “We started getting calls from all over the industry,” Dr. Channaiah said. “This is the first time research about pathogen destruction in the bakery has been done. It will help a wide variety of bakers achieve maximum food safety.”