Most people prefer shiny apples to dull ones, crisp French fries to soggy ones, and fresh nuts to stale ones.
Enter food coatings. Some are visible and some are invisible, but they’re on much of the food you buy, keeping it fresh-tasting and -looking longer.
It’s not easy. After all, the coating has to be edible and either taste good or taste like nothing at all. Depending on the food it’s applied to, it may be called upon to prevent oxidation, limit moisture and oil transfer and stabilize the food during freezing and thawing. It also has to be able to be applied, stick and stay stuck to all kinds of different surfaces under a wide range of conditions, without causing the coated food to stick to itself.
Many commercial food coatings are similar to coatings you use at home. The basic food coating is probably batter. So-called adhesion batters are similar to the egg-and-milk dip you may use at home–they’re designed to make something else, such as bread crumbs, stick to the food. Commercial adhesion batters aren’t made of egg and milk, however; they consists of several different starches combined with carbohydrates such as gums.
The other main type of batter, tempura batter, also includes a leavening agent such as baking soda, so that it puffs up.
Not all food coatings are as visible as batter. Commercial French fries, for instance, which must stay crisp for up to half an hour under a heat lamp, are coated with up to five different starches to keep them from wilting.
Confectionary items–candies and chocolates–are also coated, to make them smooth, shiny and scuff-resistant. Confectionary glazes typically contain shellac (yes, the same stuff that used to coat furniture). One of the oldest food coatings known, shellac, harvested in India and Thailand, is secreted by tiny female insects (Laccifer lacca,to be precise) as a protection from predators. (If the thought of eating an “insect secretion” bothers you, just remind yourself where honey comes from.)
Fruits and vegetables are also often coated with edible films to prevent deyhdration, decrease oxidation (which makes vegetables turn brown), delay ripening, and protect against bruising and other damage. Like confectionary glazes, fruit coatings typically contain shellac, with a few anti-foaming agents added to make spraying the fruit with the coating go more smoothly.
Scientists are hard at work developing new methods of coating food to help it keep its freshness and visual appeal even longer–so a refrigerated slice of apple, for instance, could retain its fresh-cut look for up to three weeks, instead of turning brown in short order.
Researchers at Food Science Australia, for example, are looking at creating more coatings made from naturally occurring compounds found in the foods themselves. Called modified atmosphere coatings, or MACs, these new coatings would allow only certain gases to pass through, preventing the food’s deterioration without the need for plastic packaging.
At the University of Georgia, food science and technology professor Manjeet Chinnan is studying both existing and new coatings and “edible films”–wrapping material that is made from plants instead of plastic. Edible films–based on the plant-based wrappings people in Asia have been using for centuries for various foods, such as sticky candies–being either eaten or at the very least biodegradable, could greatly reduce waste and the use of natural resources, since they’re often made from food-processing byproducts. They’ve found limited use so far, but further research could lead to their gradually supplanting the ubiquitous plastic film almost everything is wrapped in today.
Chinnan has discovered coatings that can increase the shelf life of foods like roasted peanuts by up to 60 percent and plant-based coatings that reduce the fat absorption of fried chicken strips by up to a third (and the chicken remained moister, to boot). Other coatings he’s studied prevent the fats and acids in food being fried (vinegar and lemon juice in a marinade, for instance) from migrating into the frying oil, which keeps the frying oil fresher and allows it to be used longer.
And in the future? Well, Chinnan’s team hopes to engineer films that could transfer flavors to foods, add vitamins, or even contain anti-microbial agents that could reduce the risk of microbial contamination, and hence the risk of food poisoning.
For something you can’t even see most of the time, food coatings accomplish a lot.
