New Findings on Sour Taste
By Rosalie Marion
Bliss July 5, 2007
Food manufacturers may soon have more control over the amount of
sour taste that comes through in a variety of acidified food products.
The study, led by Agricultural Research Service (ARS) food technologist
Roger
McFeeters, will appear in the August issue of the Journal of Food
Science. He and colleagues in the ARS
Food
Science Research Unit, Raleigh, N.C., worked with
North Carolina State University-Raleigh
researchers. ARS is the U.S. Department of
Agriculture's chief scientific research agency.
Sour is one of only five primary human taste sensations, and is
stimulated by organic acids. Some organic acids are naturally present in foods,
such as the citric acid in oranges, malic acid in apples and, as a result of
fermentation, the lactic acid in yogurt. These and other organic acids may also
be used as food ingredients.
Because taste is a subjective perception, nine volunteers were trained
to evaluate the intensity of sourness, plus several other sensory attributes.
The volunteers were presented with test solutions containing eight different
organic acidseither with one acid at a time, or as a mixture containing
three of the acids.
Organic acids are molecules characterized by the presence of carboxyl
groups, which is what makes them acidic. Surprisingly, molecules of all eight
organic acids were perceived to be equal in sour taste provided that at least
one carboxyl group in a molecule had a hydrogen ion attached to it. When no
hydrogen ion was attached, no sour taste was detected at all.
These chemical relationships were also tested in a food. Fresh-packed
dill pickles were made using the same organic acids used in the test solutions.
Taste tests showed that the sour taste intensity increased in direct proportion
to the total number of all organic acid molecules in the pickles that had an
attached hydrogen ion.
This new insight will help food processors more efficiently control
sour taste intensity when formulating acidified foods, such as sour candies,
cream dressings, dill pickles, dough breads and tangy beverages.