Food Processing Balancing Act: Maintaining Flavor and Nutrition in Processed Foods

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Jennifer Acuff and her team at the University of Arkansas System Division of Agriculture developed a food processing method that optimizes the preservation of vitamins, minerals, and flavor in low-moisture foods like powdered milk. This new framework allows the food industry to tailor safety standards within FDA guidelines, ensuring both consumer safety and product excellence.

Food processors often use heat for pasteurization or sterilization to make food products safe by killing pathogens like salmonella and listeria, but high temperatures can degrade food quality. To ensure food safety, the industry sometimes relies on overly stringent standards that unnecessarily reduce food quality, said Jennifer Acuff, assistant professor of food microbiology and safety for the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture.

Focusing on low-moisture food products like powdered milk, Acuff and her team performed a study seeking a method that guarantees food safety while retaining the most vitamins, minerals and flavor depending on the food. “This collaborative approach encompassed microbiology, engineering, and statistics to provide the food industry with what we believe will be a tool to improve safety without compromising quality of their dried food products,” Acuff said.

The process is not limited to low-moisture foods and may extend to other foods and processes, Acuff added. Using data from a study on a harmless “surrogate” microorganism and a statistical technique called “bootstrapping,” the researchers developed a framework to provide food processors options within U.S. Food and Drug Administration guidelines.

“We have proposed a methodology to pick a value between the most liberal and most conservative food processing approaches based on risk tolerances,” said Jeyam Subbiah, head of the food science department. “The industry can use this methodology to pick a value and petition the FDA for approval.”

While there is no specific FDA rule, the government currently asks the food processing industry to make a petition for a case-by-case review.

“Surrogates are like dummies used in crash testing to validate car safety,” Subbiah said. “They are non-pathogenic microorganisms, which should have similar or higher heat resistance than the actual pathogen. Often, they are a lot more resistant.”

Calculating the Risk

As a food science graduate student in the Dale Bumpers College of Agricultural, Food and Life Sciences, Arshpreet Khattra used previously published data from Subbiah’s lab involving the surrogate Enterococcus faecium to develop a solution for preserving quality in thermal processing. She applied the bootstrapping technique to estimate the distribution of kill ratio in milk powders rather than calculate the “simple mean,” or average, kill ratio.

With bootstrapping, scientists can deal with uncertainty in experimental data by generating many samples instead of assuming a specific distribution. The technique calls for randomly picked data points from the original data to give researchers a good idea of how much the results may vary due to chance. It has been used in various studies to improve food processing methods and assess the food safety risks of different microbes in various foods.

From the estimate of kill ratio distribution, the final kill ratio can be calculated on a sliding scale of risk, Subbiah noted. In a hypothetical example, to have a 1 percent risk level, a processor may want a 9-log reduction of the surrogate, which is a 99.9999999 percent reduction. A 5 percent risk level would call for an 8-log reduction, and a 10 percent risk would call for a 6.5-log decrease of the surrogate to be equivalent to a 12-log reduction of the pathogen. A 12-log reduction is typically called sterilization and a 4- to 5-log reduction qualifies as pasteurization.

This method strikes a balance between killing harmful bacteria and preserving quality, Subbiah said.

Khattra is now a Ph.D. student at Michigan State University. Co-authors of the study included Subbiah, Acuff, Kevin Thompson and Andy Mauromoustakos with the Division of Agriculture’s Center for Agricultural Data Analytics, and Surabhi Wason, Ph.D., now with Kerry Ingredients & Flavours in Wisconsin.

Khattra examined data collected in a 2021 study evaluating Enterococcus faecium as a surrogate for salmonella in milk powders at different storage times and temperatures. Subbiah was a co-author of the study led by Xinyao Wei when they were at the University of Nebraska-Lincoln. A wide range of foods incorporate powdered milk, including candy bars and baby formula.

Original Article: Bootstrapping for Estimating the Conservative Kill Ratio of the Surrogate to the Pathogen for Use in Thermal Process Validation at the Industrial Scale; DOI: 10.1016/j.jfp.2024.100264

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