[follow the Wikipedia links]
Read these four words then close your eyes for a moment, imagining your favorite foods for each
Now consider any berry you like -- grapes are a berry nearly everyone enjoys, so let's choose that one.
-
-
the skins often are
sour, especially for the darkest grapes
-
grape seeds are
bitter in taste for many consumers, so breeders have made many grape varieties seedless (losing the high nutrition of grape seeds!)
-
These four taste 'primaries' are often called the basic human tastes: sweetness, sourness, bitterness, saltiness.
There's a fifth taste, however, revealed by Japanese research 100 years ago, but not understood by modern science until the 1980s. It is now undergoing intensive research to explain how it actually is processed in the brain.
What is it?
Umami
(
"oo-ma-mee"
-- meaning "deliciousness")
Umami, or savoriness, was first suggested as the fifth basic taste based on the non-salty sensations stimulated by monosodium glutamate used in ancient Japanese cooking to enhance flavors, and still used today by many restaurants and chefs.
What is the mechanism for how umami is sensed?
The umami sensation begins when glutamic acid -- made in the human body, but a natural amino acid in many foods -- or synthetic glutamate in food binds with a tongue protein called a sensory receptor.
Glutamic acid is found in many protein-rich foods, including meat, milk and seafoods. It is particularly concentrated in cheese, especially aged or fermented ones.
Once the glutamic acid and receptor are bound together, the receptor initiates a neural signal, firing off taste cells that transmit information rapidly to a specific region in the brain called the orbitofrontal cortex (inside the brain behind the eyes).
Facts
* it is now believed by scientists that each of the 5 taste sensations has its own set of receptors closely mapped across the tongue
* in the brain, the map for the taste of umami-glutamate is separate from that of other taste stimuli like sweet, salt, bitter, sour
* umami neurons display ability for satiety, indicating that taste receptors in the mouth may communicate with the brain to stop eating! -- very cool
* glutamic acid is a major transmitter for stimulating cells throughout the nervous sytem
* umami flavor is strongest when combined with aromas -- meaning that umami acts simultaneously with aromas, texture and sight of food, creating that feeling of imminent satisfaction when appealing food is first presented -- we've all experienced this
* the above information indicates that drugs could be specifically designed to turn off interest in certain tastes, possibly leading to therapies against eating disorders
The research on umami has been very active over the last 25 years.
Here's a good summary from 1999 (click!)
Another major review is expected soon!
Fun articles on umami from the 2007 popular press
Do berries stimulate umami?
From measurements available to date,
only goji berries and açaí are naturally rich in glutamic acid
Examples
-
goji, 1882 mg per 100 g serving, an amount equal to flaxseeds (by comparison, spinach has 343 mg)
-
açaí, 800 mg per 100 g
-
saskatoon berry, 212 mg per 100 g
-
strawberry, 90 mg per 100 g
-
blueberry, 91 mg per 100 g
-
grape, 133 mg per 100 g
-
low-fat cheese, 1460 mg per 100 g
One more interesting hypothesis: a sixth taste may exist --
one for polysaccharides (complex sugars),
which would also lead to taste stimulation by
goji and açaí. Both are rich in polysaccharides.
Conclusion:
Most berries with known low levels of glutamic acid would not likely stimulate umami.
From currently available data, only goji and açaí have sufficient glutamic acid concentration to stimulate umami, possibly giving them a unique "deliciousness" factor absent in other berries.
Goji (wolfberry, Lycium barbarum L.), rich in glutamic acid content
Açaí (Euterpe oleracea Mart.)
