Edible coatings for added vitamins

The technology could be used by food makers under pressure to respond to consumer demand for healthier foods. There is also growing interest in the use of coatings to protect against food poisoning bacteria.

Researchers at Oregon State University's​ department of Food Science and Technology combined chitosan, a fibre found in crab and shrimp shells which is also a raw material for nutraceutical products, and the protein from egg whites, lysozyme, to create an anti-microbial food wrap.

The product looks like a sandwich wrap yet is thin enough to have no effect on the texture of the food it covers.

"You can use it as a film to wrap foods or you can use it as a spray or dip to coat foods,"​ said Yanyun Zhao, a food technologist and specialist in value-added products.

"And you can enrich the film or coating with extra nutrients, such as vitamin E and calcium, to boost the nutritional value of the food,"​ he added.

There is currently growing research into the use of edible coatings as a means of biodegradable packaging and for a protective coating against bacteria. But they could also be a good delivery format for nutrients.

Scottish sausage casings maker Devro recently announced it was hoping to produce collagen films to deliver a novel cholesterol-lowering technology developed by Irish biotech firm Alltracel.

Other ingredients used in edible coatings include casein, manufactured in a process patented by the ARS. The research institute has also developed coatings made entirely from fruit and vegetables.

Edible films, acting as stand-alone sheets rather than coatings which adhere directly to the product, are more widely used by the nutritional products industry, with a number of products such as vitamin C strips being launched on the European market in recent months.

The technology has previously been developed for breath fresheners, marketed by confectionery leaders such as Wrigleys.

Both films and coatings can act as a barrier to outside substances while protecting a product from damage or contamination.

Oregon researcher Zhao has found that the natural polymer in chitosan inhibits the growth of microbes that cause rot in fresh berries and other foods. Co-researcher Mark Daeschel, a microbiologist and specialist in food safety, has been working on lysozyme as a naturalpreservative in beer and wine. He has demonstrated that the egg white protein was just as effective as chemical sulphites in preventing unwanted microbial growth, without compromising the taste or quality of the product.

The scientists say that the two key ingredients each have particular antimicrobial properties that could enhance the other if combined.

They are now working on practical applications for the food wrap, with potential uses including packaging for ready-to-eat meats such as hot dogs and sausages; packing films for cheese slices, blocks and sticks; and coatings for sliced fruits and vegetables that are highly perishable.

A patent application has been filed for the technology.