Pea-starch film protects foods against microbes

Researchers at the University of Manitoba have made bioactive edible films and coatings from the starch of yellow field peas to improve foods’ quality and safety.

Dr. Jung Han, formerly of the U of M’s Department of Food Science, said in a release this week that his main goal was to make a bioactive material delivery matrix — a neutralm food-grade material — that could contain or incorporate various kinds of bioactive components.

Han’s project was funded by the Western Grains Research Foundation’s Endowment Fund.

“The raw materials I used were ingredients from yellow peas. It was food grade and needed to work as an inert coating material, to provide continuity over the whole structure,” Han said.

“The taste and texture would be neutral, but it had to be able to hold or carry the bioactive ingredient without changing its own properties. It’s dried, it’s a biodegradable plastic film. If it’s not dried, it could be a gel or coating material.”

Surface coating

One system Han developed was a wet pea starch gel coating applied directly to the surface of perishable foods, to isolate the food from the environment and reduce microbial contamination.

“This starch coating layer contained natural preservatives, natural antibiotics, or natural herbs and spice extracts which are natural anti-microbial agents. It killed the harmful bacteria wonderfully, without changing the population of good bacteria like lactic acid bacteria,” he said.

“Those are important issues for food safety. I used sliced chicken, drumsticks, fruits and cheese, coated with the pea starch coating layer. It preserved the foods against microbial contamination.”

Han developed a spray coating product that can be applied directly on a chicken carcass, to prevent cross-contamination of microorganisms, from carcass to carcass. It can be applied with the inside-outside body washers currently used in the poultry industry.

The University of Manitoba owns the rights to the technology and is now shopping it around to various commercial interests, the WGRF said in a release.

Han also developed a microencapsulation process using pea protein. The edible microencapsulation material can be used to protect beta-carotene and fish oils, and may also be used to preserve flax seed oil for the health food industry.

“The oil is highly sensitive to oxidation. The oil is captured within a shell made of pea protein, to form a powder that can be used as a nutraceutical food ingredient,” Han said. “It makes a very shelf-stable product that is water soluble. If it’s added to food, the oil is then released from the shell.”

Biodegradable plastic

While there is a developing biodegradable plastic industry that uses polylactic acid (PLA) derived from corn, Han’s work focused on making a similar plastic product from peas. He successfully developed a biodegradable plastic using pea starch.

“Making the pea starch film is easy because I used a regular extruder. It melts or gelatinizes the pea starch and rearranges the polymers’ direction. The starch bundles that form are resistant to digestion by enzymes,” he said.

Starch-based plastic-like compostable containers can be made from potato starch, but Han said that product is mechanically weak. Adding pea starch to the mix helps increase its mechanical strength. Han says pea starch plastic is mechanically very strong.

Using biodegradable plastic for silage bags could be one commercial fit for the product, he said. After the plastic is used, it would degrade in moist soil within a couple of months after disposal.

He concluded that dried pea starch films can be used as a food wrapping or within the food, to separate food components. The resistance of the films to high relative humidity makes these films useful with moist foods.

“Pea starch film is strong, has intermediate stretchability and good barrier properties at high relative humidity, which make it applicable on intermediate and high moisture foods. It can be sprayed plain or carry functional ingredients on dried fruits, bread, chocolate and nuts,” Han said.

A pea starch-based antimicrobial coating showed suitability to be used on raw chicken. The coating enhanced the antimicrobial activity of certain food preservatives.

“The coating increased the contact time between the antimicrobial and the targeted microorganism,” Han said. “The applicability of this coating on other foods such as beef, nuts and dried fruits has potential to open a new market for pea starch.”

CLARIFICATION, Oct. 9: The WGRF’s release described Dr. Jung Han as a faculty member in the U of M’s faculty of agriculture and food sciences. Dr. Han in fact left the U of M in 2007 to become a senior research project engineer for Frito Lay North America in Plano, Tex.

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