I love it when Chapman talks about low-moisture foods

A number of recent outbreaks related to pathogens in low-moisture foods have created urgency for studies to understand the possible causes and identify potential treatments to improve low-moisture food safety.

ben_chapman2Thermal processing holds the potential to eliminate pathogens such as Salmonella in low-moisture foods. Water activity (aw) has been recognized as one of the primary factors influencing the thermal resistance of pathogens in low-moisture foods. But most of the reported studies relate thermal resistance of pathogens to aw of low-moisture foods at room temperature. Water activity is a thermodynamic property that varies significantly with temperature and the direction of variation is dependent on the product component.

Accurate methods to determine aw at elevated temperatures are needed in related research activities and industrial operations. Adequate design of commercial thermal treatments to control target pathogens in low-moisture products requires knowledge on how aw values change in different foods at elevated temperatures.

This paper presents an overview of the factors influencing the thermal resistance of pathogens in low-moisture foods. This review focuses on understanding the influence of water activity and its variation at thermal processing temperature on thermal resistance of pathogens in different low-moisture matrices. It also discusses the research needs to relate thermal resistance of foodborne pathogens to aw value in those foods at elevated temperatures.


Influence of water activity on thermal resistance of microorganisms in low-moisture foods: A review

Comprehensive Reviews in Food Science and Food Safety

Roopesh M. Syamaladevi, Juming Tang, Rossana Villa-Rojas, Shyam Sablani, Brady Carter, and Gaylon Campbell


Fruitcake – Will It Last Forever?

Chris Murphy of Sloan (a top-5 band on the pantheon of Canadian rock and roll) pines on Action Pact that ‘nothing lasts for ever any more.’

Fruitcake might.

But as Schaffner says, ‘it depends’ on some a few factors.

My friend and colleague, Matt Shipman from NC State News Services tackled the question  of fruitcake preservation on The Abstract, the first of a series of holiday posts.

I’ve always thought that, in the event of a nuclear apocalypse, the Earth will be populated solely by cockroaches, those Styrofoam hamburger containers that fast-food joints used in the 1980s, and fruitcakes. Since this is the season for loved ones to inflict fruitcakes on one another, I decided to get to the bottom of this mystery: will fruitcakes really last forever?Fruitcake-848x477

As it turns out, the answer depends on how you define “fruitcake.” 

Most fruitcake recipes include dried nuts, dried fruit, and “candied” fruit or peel (meaning the fruit has been both dried and preserved in sugar). [Note: not all fruitcakes are made this way, see the safety note below.]

The U.S. Department of Agriculture says that fruitcake will last two to three months in the refrigerator without spoiling, and will maintain its quality if stored up to a year in the freezer. But it’s a federal agency’s job to think of the worst-case scenario. Could fruitcakes really last longer? (and FDA says that the water activity of a fruitcake, although there’s not a standard identity for one, is between .73 and .83 – ben)

“All of these dried and candied ingredients have what we call ‘low water activity,’ meaning they have very little moisture available,” says Ben Chapman, a food safety researcher at NC State. “Low water activity is important because many microorganisms, including foodborne illness-causing bacteria, need moisture in order to reproduce.

“In practical terms, this makes most fruitcakes extremely shelf stable, so they would be safe to eat for a long time – a really long time,” Chapman says. “But it might taste pretty bad.”

That’s because a lot of things can significantly affect the quality of the fruitcake.

For example, mold could grow on the surface of a fruitcake, or yeast could cause some of the sugars in the fruitcake to ferment.

“But some people wrap their fruitcakes in linen that’s been soaked in rum or other spirits to reduce the chance of mold or yeast problems,” Chapman says.

“However, rancidity may still be an issue. Fruitcakes contain a variety of proteins, from eggs to butter to nuts – even the fruit items. And when proteins are exposed to air, they can become oxidized, which can create rancid flavors and odors,” Chapman explains.

So, while you may be able to save that fruitcake forever, you should probably eat it now.

Safety Note: If a fruitcake has a significant amount of moisture (e.g., if it was made with fresh fruit) it is more likely to spoil or to give pathogens enough moisture to reproduce. In other words, it could make you sick if not kept refrigerated and eaten relatively quickly.