Progress 01/01/04 to 12/31/06
Outputs
Progress Report 4d Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and NC State University. Additional details of research can be found in the report for the parent project (6645-41420-004-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-quality, Nutritious Safe Products and Reduce Pollution. The objective was to test our recent hypothesis for the relationship between the ionization of organic acids and their ability to cause sour taste. Results of the project confirmed our hypothesis both in water solutions of acids and in a fresh pack dill pickle product. This outcome provides significant new insights about sour taste. Implications of these results are that (a) common organic acids in foods are all equally sour on a molar basis, (b) that all species of an organic acid with one or more protonated carboxyl groups are equally sour, (c) that the
hydrogen ion is about equal in sour intensity to a protonated organic acid molecule. It was also found that within the pH range of most acid or acidified foods (pH 3.0 to 4.6) the hydrogen ion itself will have very little direct contribution to the total sour taste of a solution or a food. It was also observed that in a pickle product the sour intensity of the acids is substantially suppressed compared to their sour intensity in simple water solutions. The chemistry of this taste suppression effect is not yet understood. Since there is a linear relationship between sour flavor intensity and the molar concentrations or all organic species in a particular type of food, it will be possible to predict changes in sour intensity that result from substituting different acids in a product or from changing the pH of a product. However, because the sour suppression effects of different food components are not known, it is not yet possible to create a general model for predicting sour flavor
intensity in foods. These results provide new understanding of the acid chemistry that elicits sourness as a basic human taste perception.
Impacts
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Progress 10/01/04 to 09/30/05
Outputs
4d Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and NC State University. Additional details of research can be found in the report for the parent project (6645-41420-004-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-quality, Nutritious Safe Products and Reduce Pollution. Sour taste intensity was measured by a descriptive sensory panel (n=9) using the SpectrumTM method. The distribution of organic acid species in solutions was calculated using pHTools, a modeling program implemented in MATLABTM. Sour taste intensity increased linearly with total concentration of protonated acid species at pH 3.5, 4. 0, and 4.5, regardless of the acids present in the mixtures. Slopes of the three regressions were not significantly different, but the intercepts increased with decreasing pH. At constant protonated acid concentration, sour taste intensity decreased
significantly as pH and, consequently, concentration of sodium salts of these acids increased. These results confirm the hypothesis regarding the linear relationship between sour taste intensity and protonated acid species and suggest that sodium salts of acids suppress sour taste. Implications of these results are that all organic acids are equally sour on a molar basis. For acids that have more than one acid group, all species of the acid with one or more hydrogen ion attached to the molecule will also be equally sour.
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Progress 10/01/03 to 09/30/04
Outputs
4. What were the most significant accomplishments this past year? This report serves to document research conducted under a specific cooperative agreement between ARS and NC State University. Additional details of research can be found in the report for the parent project (6645-41420-003-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-quality, Nutritious Safe Products and Reduce Pollution. A sensory panel was selected and trained to taste sourness, sweetness, bitterness, saltiness, and astringency by the Spectrum method with a 15-point rating scale for the intensity of each basic flavor attribute. Initial data on the taste intensities of acid mixtures of acids has been collected.
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