Novel Packaging Technologies Maintain Functional Foods' Goodness

01/09/06 The popularity of “functional foods” containing healthy or supposedly disease-preventing ingredients has grown vastly in recent years. Health-conscious consumers can now buy bread, margarine, cereal, baby food and dairy products stuffed full of added vitamins, minerals, omega-3 oils and antioxidants, as well as both probiotic bacteria and prebiotics – ingredients supposed to promote the beneficial bugs.

There is, however, growing evidence that many of these ingredients fail to deliver whatever benefit they may have, either because they degrade during manufacture and storage of the product, or because our bodies simply break them down before they can do us any good. Up to 90 per cent of some probiotic bacteria used in yogurt drinks for example, including bifidobacteria, do not survive the journey through the stomach to the small intestine. Similarly, omega-3 fatty acids that are believed to boost brain power can become oxidised if exposed to oxygen, which not only makes the oils taste and smell rancid, but produces damaging free radicals.

Now New Scientist writes that the food industry is investigating a range of technologies to protect these vulnerable ingredients. Some involve encasing the ingredients in protective capsules, while others are looking at novel packaging technologies to seal the good stuff separately until the food is opened.

One technique attracting a lot of attention is microencapsulation, developed by the pharmaceutical industry to deliver timed release of drugs into the body. Mary Ann Augustin, a chemist at Food Science Australia in Melbourne, has been using a spray-drying technique to coat fish oils in protective edible proteins or carbohydrates, as part of a programme at the Australian national research institute CSIRO. “This has enabled the conversion of fish oil into shelf-stable powdered oil ingredients and liquid emulsions,” she says. Some of these are already available in bread and baby milks.

Not only does this prevent the oils oxidising during storage, it should also prevent them altering the texture and flavour of the food, says Jose Maria Lagaron, who is leading a study into using novel materials and nanotechnology in food packaging at the Agrochemistry and Food Technology Institute in Valencia, Spain.

This simple encapsulation technique is enough to protect fish oils from the atmosphere, but ingredients such as probiotics and prebiotics need protecting from stomach acids. This means developing a coating to delay their release until they reach the intestine. “It’s a very tall order,” says David Weitz, a material scientist at Harvard University. One simple approach is to encapsulate the ingredients in colloidosomes – porous, crystalline molecules that release their contents gradually. “Just by having tiny pores in the surface you get diffusion over a certain amount of time, so you get a slow release,” says Weitz.

However, most progress in this area has been made in encapsulating the bacteria within spheres of digestible “biopolymer”, such as a polysaccharide . A number of labs, including Lagaron’s, are developing biopolymer capsules designed to release their contents in response to different triggers, such as a particular pH or light level, or even the concentration of ions in their environment.

How consumers will take to the technologies also remains to be seen. There have been protests that adding folic acid to bread or fluoride to water amounts to mass medication. What’s more, the industry need only look at how European consumers responded to genetically modified food to see what they might be up against, says Frans Kampers of the Wageningen Bionanotechnology Centre for Food and Health Innovations in the Netherlands – particularly if they are associated with the term “nanotechnology”.

If these problems can be overcome, however, such techniques could ultimately improve the nutritional value of foods, and improve their absorption by the body, Kampers says. For example, the industry has started adding flavonoids – oily substances found in vegetables such as broccoli that are believed to act as antioxidants – to a range of foodstuffs, including spreads and drinks. Flavonoids are more easily absorbed by the body as small droplets, but such droplets tend to clump together when added to drinks or spreads, so researchers are attempting to suspend even smaller droplets within an emulsion. The oil is passed through a sieve to create uniform, nanometre-sized droplets. These are then added to the spread or liquid and blended together.

“We want to look at adding nutrients to food in such a way that the bioavailability of the nutrients is increased,” says Kampers. If researchers succeed in their efforts, it could bring a new meaning to advertising slogans like “bursting with goodness.”