It's something in the taste, not the smell, of fat that lures us to rich foods, a Purdue University scientist said on Monday. Wearing nose plugs, human subjects given a taste, but not a whiff, of cream cheese and crackers stimulated an immediate rise in their blood fat levels, while those given a sniff but not a taste did not show a rise.
"This tells us that taste is the stimulus that causes the rise in blood fat levels. The taste, and not the smell, is what the body is responding to," Richard Mattes, a Purdue professor of foods and nutrition, said in a statement summarizing findings he published in the journal Physiology & Behavior. Experiments with rats and mice also show they preferred fatty foods, even when their olfactory sense was short-circuited. Fat has been thought of as a tasteless "flavor carrier" that could deliver tasty compounds derived from other parts of food, and as a food component that provided texture.
But if Mattes' fat findings hold up, science may have to include it in the list of five flavors human palates can detect: sweet, salty, sour, bitter, and "umami," which is evoked by monosodium glutamate (MSG) in foods. Our physiological response to the taste of fat may explain another mystery: Why don't fat-free foods taste as good? "I wonder if the less-than-perfect performance of current fat replacers may be due to a lack of understanding of all mechanisms for fat perception," Mattes said.

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