Dry spices

Whenever a Salmonella recall hits the front page, our typical knee-jerk reaction is to blame the chicken. We don’t usually think about pointing the finger at the peanut butter that’s been in the fridge for a month or at the potato chips we bought just last Tuesday.

But, thanks to new technologies, we’re now better able to track outbreaks, and poultry may be vindicated, no doubt much to the chagrin of the peanut butter and potato chips.

Historically considered impervious to pathogens, low-water activity, aka low-moisture, foods have recently been implicated in several Salmonella-related recalls.

To learn more about the contamination risks associated with low-moisture foods and how processors can mitigate these risks, we spoke with Elizabeth Grasso-Kelley, a researcher at the Institute for Food Safety and Health (IFSH), which is a unique collaboration between the Illinois Institute of Technology (where Grasso-Kelley is an assistant professor), the FDA, and the food industry. Last semester, Grasso-Kelley served as a PROCESS EXPO Expert-in-Residence, writing about the problems associated with low-moisture foods and some of the studies she has led investigating solutions to these problems.

Misconceptions surrounding the safety of low-moisture foods

The food safety problems associated with low-moisture foods aren’t new. They’ve just been difficult to track. This has led to a general misconception that these foods were safe. But the recalls above, and others like them, have shown that spices, flours, nut butters, and similar foods may also be the source of contamination. Since low-moisture foods are a relatively new focus area for the industry, there are several misconceptions about their food safety.

Misconception #1: If pathogens can’t grow on food, you’re in the clear

Grasso-Kelley says that the biggest misconception she encounters is the idea that just because pathogens can’t grow on low-moisture foods, those foods are automatically safe.

This isn’t true, and it can be a dangerous idea. Grasso-Kelley noted in her article “When No Growth ≠ Safety” that the past decade has seen 16 outbreaks of Salmonella in low-moisture foods, accounting for one-fifth of the total reported outbreaks during that time. These incidents resulted in more than 350 people being hospitalized and 11 fatalities.

In fact, pathogens in low-moisture foods can be even more difficult to kill than those in other foods because as moisture content decreases, pathogens become even more resistant to heat, which leads us to misconception #2…

Misconception #2: If we heat it, it will be safe

For most foods, the best way to ensure safety is through thermal processing — cooking, pasteurization, canning, and so on.

This approach doesn’t work for dry foods. First, as mentioned above, the pathogens tend to be highly heat-resistant. Grasso-Kelley notes that the research shows that applying traditional heating processes to low-moisture foods results in barely any change in pathogen levels.

In addition, thermal processing is undesirable for many of these foods because heat would change the flavor profile and other characteristics of the food. That means processors of low-moisture foods need to take innovative approaches to ensure the safety of their products. This is Grasso-Kelley’s main research focus, and we’ll come back to it in the next section of the article.

Misconception #3: Food safety efforts should focus on the cold spot of the product

For products where thermal processing is an effective form of pasteurization, the traditional approach is to focus on the coldest part of the product to make sure it achieves the desired temperature for the specified time.

Again, low-moisture foods don’t follow the traditional pattern. In fact, Grasso-Kelley says, in some cases, it’s quite the opposite. The most difficult place to kill pathogens live is the outer surface of the product. If you heat these products and then dry them quickly, the process can create a crust on the outside that preserves the bacteria rather than killing it.

Technologies to control pathogens in low-moisture foods

In addition to not following traditional patterns, low-moisture foods pose a few other unique food safety challenges.

The biggest one, Grasso-Kelley says, is that you can’t always include water in the processing. In other areas of the industry, you could just clean with water, but for low-moisture foods this can exacerbate the problem. Also, for many foods, if you don’t hit your desired time-to-temperature targets during the pasteurization step, you can just re-pasteurize the product — no harm done. But for low-moisture foods, it’s not easy to recondition the products using the same technology and parameters.

So, if traditional approaches don’t work, what are processors to do? FSMA has raised the regulatory stakes, and a recall can easily put a company out of business.

Grasso-Kelley is currently part of a team working on solutions to this problem with the support of a large multi-institution grant from the USDA. Their goal is to explore new technologies as well as legacy technologies — equipment like ovens, extruders, and fryers that processors might already have in their plants, but aren’t currently using for food safety. “We’re looking at whether we can use these technologies to make products safe,” she says, “and at how processors can get more bang for their buck.”

Here are a few of the approaches the group is investigating:

  • Steam injection — Initial studies show it may be effective to insert a steam injection step into the beginning of the process (i.e., start with higher moisture at the beginning than the product will have at the end)
  • Gasses — Gasses currently used to fumigate nuts can also be used for other foods where heat treatment is undesirable, like spices
  • Cold plasma
  • Radiofrequency technologies

Grasso-Kelley’s area of expertise is the legacy technologies, specifically, how to use thermal processing equipment for low-moisture foods. This is a key area of research because many smaller processors can’t immediately go out and purchase new equipment, especially novel technologies, which tend to have higher upfront costs.

“New technologies are cost additive at the front end,” Grasso-Kelley says. “With FSMA, people are looking at these niche technologies, and they will become more mainstream. But we still need more research on their efficacy, and then we need to focus on how we can drive down the operating costs.”

In her research, Grasso-Kelley emphasizes the importance of taking a two-pronged approach to using legacy equipment:

  1. Maximizing kill for the food product — “Make sure you have clean product going in, and you’ll get a safe product coming out.”
  2. Sanitation of the food processing equipment — Processors need to take control measures to ensure the equipment itself is properly sanitized, without the benefit of the industry’s most widely used cleaning agent: water.

In one of her Expert in Residence articles, Grasso-Kelley summarized the results of a study she conducted to investigate the efficacy of a new cleaning and sanitation procedure for peanut butter processing lines contaminated with Salmonella. They found that by circulating the lines with hot oil and then with 60% isopropanol, they were able to reduce the pathogen to an undetectable level.

Getting technologies to market

One key advantage of the IFSH program is that it brings different stakeholders together and encourages collaboration. In the area of low-moisture foods, Grasso-Kelley says, researchers and industry partners aren’t trying to hide trade secrets or protect their research. They’re working together to approach the problems in different ways. They’re also keeping their eyes open for new opportunities. A portion of the grant is set aside to investigate new ideas that present themselves as the researchers dig in. “We’re staying open to new technologies because we know things can change day-to-day in the field.”

This flexible, collaborative approach facilitates one of the main aims of the USDA grant, which is to bring new technologies to the marketplace and make them affordable and accessible for processors.

With FSMA, that can’t happen soon enough, and processors are ready to move. Grasso-Kelley says that many small companies contact the consortium for help because they want to be doing the right thing for food safety. Many of these companies make products used by larger companies, and they need to be in compliance as quickly as possible to remain on the approved supplier lists.

“We won’t bring something out in Year 1 and have it be mainstream by Year 5,” Grasso-Kelley says. “But our goal is to hasten that. The FDA is working to gather data and perform validation studies and make these technologies more available. Once a technology is shown to be effective, it doesn’t take that long to become generally accepted.” That’s good news for the industry and consumers alike!

If you’d like to learn more about what Grasso-Kelley and the folks at IFSH are up to, visit the organization’s website. And for more information about how to control Salmonella in low-moisture foods, check out this technical guidance from GMA.