Natural antimicrobial agents for food safety

Two items high on the list of public concerns are the need for greater food safety and a growing demand for natural or organic food products.

Understanding this, chemists and food scientists at Rutgers, The State University of New Jersey, joined forces to develop natural approaches to the prevention of food contamination and spoilage.

The results of the breakthrough Rutgers research will be presented at the 234th national American Chemical Society meeting in Boston on Aug. 22.

The researchers employed natural antimicrobial agents derived from sources such as cloves, oregano, thyme and paprika to create novel biodegradable polymers or plastics to potentially block the formation of bacterial biofilms on food surfaces and packaging.

Typically, a variety of bacteria will congregate on a surface to form a bacterial community that exists as a slime-like matrix referred to as a biofilm. This kind of bacterial community is often described as being polymicrobial; it harbors multiple versions of infectious, disease-causing bacteria, such as Salmonella and E. coli.

"We mated natural substances with controlled-release, biodegradable polymers that could inhibit or prevent the formation of bacterial biofilms," explained Ashley Carbone, a graduate student at Rutgers who constructed the polymer compounds that were tested.

This approach offers a number of advantages. The diversity of polymicrobial biofilms makes them difficult to defeat, with each type of microbe presenting a unique challenge to health and hygiene, explained Kathryn Uhrich, professor of chemistry and chemical biology and Carbone's adviser.

"The natural substances we chose have general antimicrobial activities against many different kinds of microorganisms," Uhrich said. "Therefore, the polymers into which we incorporated these natural substances have the potential to affect a much broader spectrum of microorganisms than organism-specific drugs," Uhrich said.

Another advantage comes out of the Rutgers researchers decision to focus on the biofilms, rather than attempting to attack the individual bacteria. This avoids the potential of increasing the antimicrobial resistance of specific bacteria, an emerging problem in medical circles brought on by the overprescription of antibiotics.

An additional positive feature stems from the use of polymer backbones to which the natural agents were incorporated. These polymers are biodegradable due to their specific chemical composition and the nature of the bonds that hold them together, Uhrich explained.

"As they degrade in the presence of water and/or enzymes, they slowly release their active antimicrobials," Carbone said. "A slow and controlled release of the food-based antimicrobial would offer great advantages in the food industry, providing protection over an extended time and extending the shelf-life of the food product."

The retail marketing sector may benefit from the Rutgers innovation. With the growing consumer interest in natural foods, shoppers may be more attracted to products containing natural antimicrobial ingredients rather than the synthetic chemical additives currently in use to protect against contamination and spoilage.

"If consumers buy products containing our natural bioactives, they will benefit from all the positive factors that come along with our new strategy for food safety," said Michael Chikindas, associate professor of food science at Rutgers and a co-investigator on the project. "They will be eating foods that are safer for longer periods of time; they will not be expanding antibiotic resistance; and they will not be adding to their bodies synthetic chemical load."

As a bonus, some of the antimicrobials carry some of the flavors and aromas of the sources from which they were derived. "The food people eat might even smell and taste better," Chikindas said.

Uhrich remarked that when entering her laboratory recently, she was struck by the fragrant smell of curry. "When I asked where lunch was being served, Ashley explained there was no food in the lab and I only smelled the new polymers she was making," Uhrich said.