WASHINGTON – That fresh grassy smell wafting up from the newly sliced tomato may be its way of saying "I'm good for you."
Indeed, the odors from foods ranging from garlic and onions to ginger and strawberries may be nutritional signals that the human nose has learned to recognize.
"Studies of flavor preferences and aversions suggest that flavor perception may be linked to the nutritional or health value" of foods, researchers Stephen A. Goff and Harry J. Klee report in Friday's issue of the journal Science.
However, they caution, domestication of many vegetables has not been kind to them, tending to favor qualities like color, shape, yield and disease resistance instead of flavor and nutrition.
Flavor is complex and uniquely challenging to plant breeders, they note, and as a result has not been a high priority.
Take the tomato, for instance.
Klee and Goff analyzed two types of tomato, the wild cerasiforme and the commercially grown Flora-Duke.
Except for one chemical that also affects color, the sugars, organic acids and volatile compounds associated with tomato flavor were reduced in the commercial product.
For example, one of the volatile compounds associated with the "tomato" or "grassy" flavor is called cis-3-Hexenal, which is also an indicator of fatty acids that are essential to the human diet. They found that the wild tomato contained more than three times the amount of that chemical than the cultivated version.
Two other contributors to tomato flavor — 2- and 3-methylbutanal — are indicators of the presence of essential amino acids and are also three times more common in the wild tomato.
In addition to tomatoes, those chemicals are also important constituents of the flavors of apples, strawberries, bread, cheese, wine and beer, they reported.
Goff and Klee also noted that the scent compounds produced in many spices are associated with health properties.
For example, curcumin, which is present in tumeric, is reported to have anti-inflammatory properties, compounds in ginger have antioxidants and there are antimicrobial chemicals that contribute to the scent of onions, garlic, rosemary, sage, clove, mustard, chili peppers and thyme.
"A preference for the flavors found in these spices is believed to have developed due to the health benefit of less contaminated food," they conclude.
The odors of the compounds are of particular interest because they are a major factor in how taste of foods is perceived. The human tongue senses just five flavors — sweet, sour, salty, bitter and umami, sometimes called savory — and scent provides considerable added information about a food.
Klee is at the Institute of Food and Agricultural Science, University of Florida, and Goff works for Syngenta Biotechnology, an agribusiness company. Their work was supported by the National Science Foundation and Syngenta.