Penn State researchers have developed a biodegradable, edible film from plant starch and antimicrobial compounds that will eliminate dangerous pathogens on seafood.
The new film controls the growth of foodborne pathogens like vibrio, which naturally occurs in marine environments, and salmonella, which can contaminate seafood during production or processing. Both of pathogens are linked to gastrointestinal problems when consumed.
“We have the ability to develop a film with antimicrobial activity that can kill foodborne pathogens on food surfaces,” Catherine Cutter, a professor of food science at Penn State, said in a statement. “Given the recent outbreaks that we have seen with a number of food products, coming up with something that can be used by the industry to kill microorganisms on the surfaces of food is a noble area of research to investigate.”
Both vibrio and salmonella can survive in long-term freezing conditions, making it particularly concerning in the seafood industry. When freezing food like seafood, ice crystals form from the water in the food. The ice crystals act as “daggers” that pierce the bacterial cell wall to cause damage to the cell.
“Vibrio and salmonella are somewhat susceptible to freezing,” said Cutter. “So, if you treat bacterial cells with antimicrobials and then freeze them, the approach can be more lethal.”
As part of the study, researchers from Thailand used a blend of thermoplastic starch, which is a biodegradable polymer made from cassava, and a gelatin coating containing antimicrobials Nisin Z and lauric arginate (LAE).
They then developed a culture cocktail filled with the bacteria and inoculated slices of tiger prawn and big-eye snappers. The team then tested the seafood samples using different compositions of Nisin Z and LAE to discover which variations would give the best kill.
After dipping the samples into the edible film that included the antimicrobials, some of the slices were vacuum-sealed and chilled for up to a month, while other samples were frozen for 90 days.
“If you just dip shrimp into any antimicrobial — it’s not going to stick very well,” Cutter said. “But if you put the antimicrobial into an edible film, and then dip the shrimp into the film and pull it out, that film is going to form around the shrimp. The film then releases the antimicrobials over time.”
The researchers used “controlled release” to release the antimicrobials over in time in order to get a maximum kill, made possible by the edible film’s unique properties.
“If you’re going to make an edible film, you want to make a film that has similar properties to plastic,” Cutter said. “You want these edible films to be transparent because consumers aren’t going to buy something they can’t see, you want them to be flexible, and you want the film to mold to the food product. By using edible films, you are doing it in a way that is biodegradable.”
According to Cutter, reducing the reliance on plastic packaging remains a big challenge for the food industry.
“How do you get the industry to change something they and consumers are so used to using?” Cutter said. “This research demonstrates, through proof of concept that antimicrobial edible films work.
“So how do we get this type of packaging into a commercial application? That’s the next logical step in the progression of this type of research,” he added.
