From metal bars to candy bars; materials scientists turn to what you're eating and how you eat it

Science News,  Feb 17, 2001  by Jessica Gorman

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When Peter J. Lillford's two children were young, he saw no problem with the kids spitting out tough pieces of meat during dinner. Instead of withholding dessert until they cleaned their plates, Lillford turned his kids' finicky eating habits into a teaching too]. Out came the tweezers so the family could dissect the offending mouthfuls.

In effect, Lillford was bringing his work home. As a food chemist at Unilever Research in Bedford, England, he investigates what makes different morsels cook, feel, and taste the way they do. He and other food-focused materials scientists treat those morsels the way metallurgists treat a piece of metal. It's probed and prodded, tested for mechanical properties such as fracture and flow, analyzed with powerful microscopy, and finally put through rigorous trials in the machine where it will eventually be used. For Lillford's work, that's the mouth.

There's more science in food appreciation than the chemistry of what stimulates taste buds. Consider the research behind designing creamier varieties of butter substitutes or keeping potato chips consistently crisp. Currently, this work relies heavily on trial and error and the imperfect standards of human testers.

That's changing, however. Recent work by Lillford and other researchers is unraveling various foods' hidden internal structures and uncovering the detailed physics that underlies, say, why we enjoy the texture of some chocolates more than others. That kind of knowledge may help innovators bypass much of the current hit-or-miss process and more directly devise recipes for appealing new foods.

There are many incentives for making the food-invention process more efficient. For one, "consumers don't stand still," says Athene M. Donald, a food physicist at the University of Cambridge in England. People's tastes and demands change. Food suppliers strive to win market share by satisfying those fickle demands or by offering attractive new options.

As people work and travel more, for example, they demand a greater variety of prepared foods, says Donald. Consumers also want some traditionally seasonal foods, such as strawberries, plums, asparagus, and lettuce, to appear in grocery stores all year round. To make these products crispy, moist, and fresh tasting, even in the dead of winter, companies need to develop methods of producing and packaging them that retain their structural and textual properties.

Furthermore, materials scientists need to be aware that new packaging methods may raise issues of foodborne disease, says food scientist Peter Schroeder, past director of the Institute of Food Research in Norwich, England. For example, the controlled-atmosphere plastic bags used for ready-to-eat salad mixes may not subdue bacteria as well as older techniques, such as canning and pickling, he says in the December 2000 issue of the MRS BULLETIN, published by the Materials Research Society.

Because of this risk, food producers must carefully examine how microbes behave on products packaged in new ways, agrees Donald. Such analysis requires understanding food's microscale structures and how they might affect microbial survival.

A further incentive for food materials research: Although a company developing a new food product can train teams of testers to identify subjectively the crispness of a cracker or the creaminess of a custard, the industry lacks quantitative measures that directly correlate with these qualities.

More objective standards, such as specified microstructures, might help create consistent textures, say researchers. Then, they could design foods that will, for example, fracture with the desired crunch.

To take a materials-science approach to designing new foods or improving old ones, researchers need to learn how to predict the changes that will take place in a food's mechanical properties and structure when it is heated, cooled, pressed, mixed, extruded, and otherwise processed.

This challenge becomes even more complicated when processing food products on industrial scales. Stirring a pot on a stovetop or a beaker on a Bunsen burner is not the same as mixing ingredients in a 100-gallon vat.

"If you say that cooking is an art, the industry has to translate that into processes where they produce tons and tons and tons," says chemical engineer AnneMarie Hermansson of the Swedish Institute for Food and Biotechnology and the Chalmers University of Technology in Goteborg, Sweden.

Compared with many of the metallic, ceramic, and other substances that materials scientists study, foods usually contain much more water and are less stable, notes Donald. Furthermore, these foods have complex structures that range in size from molecules to mouthfuls.

To take on this complexity, food-focused materials scientists are trying new microscopic and other analytical techniques, say Hermansson and her col- leagues in the December 2000 MRS BULLETIN. For example, they have observed under a microscope the mixing of gelatin and maltodextrin, which is derived from potato starch.