For people who love a loaf of chewy white bread, whole wheat versions can be hard to stomach. The brown dough often carries a bitter flavor. Even the wafting smells of baking can be less appetizing when the oven contains a grainy loaf.
As part of a scientific quest to make healthy whole-grain products that taste and smell as delicious as the refined stuff, a new study zeroed in for the first time on a compound called ferulic acid, which is found in the outer layers of wheat grains. Tweaking amounts of ferulic acid, the researchers found, can alter the flavors and aromas of bread.
The discovery may pave the way for a new generation of baked goods that are both nutritious and tasty.
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"This allows us to understand how to make whole grain products more desirable so people are more likely to consume them and get the health benefits from them," said Devin Peterson, a food chemist at the University of Minnesota, Twin Cities. "We can be trained to eat things that are better for us, yes, but at the end of the day, flavor and acceptability are a huge part of what is human."
After decades of dependence on refined flours, which strip wheat grains of their outer layers, companies are making more of an effort to produce foods with whole grains, which offer fiber and antioxidants that have been linked to lower risks of cardiovascular disease, obesity, diabetes, cancer and other chronic conditions.
But the outer layers of bran and germ that remain in whole-wheat flour tend to create products that taste, smell and look less-than-appealing to many people. Even their textures can disappoint a tongue that is used to refined grains. Some products add extra sugar or salt to mask bitterness and other undesirable features, but those ingredients come with health concerns of their own.
As part of an effort to understand the chemistry that distinguishes whole-grain bread from refined-grain versions, Peterson and colleagues made bread with both kinds of flour and then analyzed the compounds in each loaf's aroma. A panel of trained sensory analysts also sniffed samples of ground-up crust to characterize the differences.
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Overall, the researchers reported in the Journal of Agricultural and Food Chemistry, bread made with refined flour had a more desirable aroma profile, with hints of corn chip, caramel, and floral notes. Whole-wheat bread was richer in cucumber, fatty and earthy notes. In both cases, chemical workups agreed with the noses of the experts.
Next, the team focused on ferulic acid, which is normally bound to wheat's cell walls but is set free during fermentation and baking. Only after it is liberated does it begin to alter the flavor and smell of bread.
When the researchers added ferulic acid to refined-grain bread, they found that its aroma resembled that of whole-wheat bread. Ferulic acid appears to suppress a compound called 2AP, which is the most important molecule behind whole-wheat bread's unique smells.
That finding served as a sort of "proof of concept," Peterson said, showing that ferulic acid plays a key role in producing the aroma of whole-wheat bread. Along with flavor, which he is also studying, aromas have a major impact on the way we experience food.
By minimizing the liberation of ferulic acid during baking, the new study suggests, it might be possible to alter the taste of the final result-eventually making whole-grain bread that is more satisfying to people who prefer white loaves. The findings might also apply to crackers, pasta, cookies and other products.
"Most companies are getting away from refined flour, especially bleached and highly refined flours, and they are going to a more or less whole-wheat approach," said Keith Cadwallader, a food chemist at the University of Illinois at Urbana-Champaign. "But when you change from normal processed or refined wheat flour to whole-wheat, the product changes substantially."
Chemistry can help companies achieve more palatable whole-grain products, he added, and it's an approach worth pursuing. But whole-grain products are never going to be a 100 percent match with refined-grain versions. At some point, people might just need to accept that eating more healthfully is going to involve new flavors, textures and smells.