Progress 10/01/05 to 09/30/06
Outputs
Progress Report 4d Progress report. This report serves to document research conducted under a USDA-CSREES- NRICGP grant no. 2003-01479. 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. This grant was awarded August 15, 2003, and an ARS account was established October 28, 2003. 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. 7. List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below). McFeeters, R.F. 2006. Food Acids and the Intensity of Sour Flavor. Pickle Packers International, Spring meeting. Da Conceicao Neta, E., Johanningsmeier, S., Drake, M.A. and McFeeters, R. F. 2006. A Chemical Basis for Sour Taste Perception. CREES-NRI Improving Food Quality and Value Project Directors meeting.
Impacts
(N/A)
Publications
- Johanningsmeier, S.D., McFeeters, R.F. and Drake, M.A. 2005. A hypothesis for the chemical basis for perception of sour taste. Journal of Food Science. 70:R44-R48.
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Progress 09/15/03 to 08/14/06
Outputs
Progress Report Objectives (from AD-416) To test the hypothesis that sourness perception in acid or acidified foods is dependent upon the concentration of organic acids in a product with at least one protonated carboxyl group plus free hydrogen ions. The specific objectives in meeting the general objective will be: (1) to determine sourness intensity of individual acids as a function of pH to evaluate whether all acids have about equal sourness and if multi-protic acids reach maximum intensity with only one carboxyl group protonated; (2) in water solutions, to test the relationship between acid species with at least one proton and sourness intensity with random mixtures of acids; (3) to validate any relationships found in objective 2 by creating acid mixtures and testing if they have a previously predicted sourness intensity; (4) to test the relationship between protonated acid species in a group of acidified vegetables and the sourness intensity with random additions of acid mixtures; (5) to validate relationships found in objective 4 by creating acid mixtures in acidified vegetable products and testing to see if they have the predicted sourness. Approach (from AD-416) A panel will be trained to quantitatively rate the sourness of mixtures of organic acids in water solution and organic acids to acidified vegetables such as dill pickles. The panel ratings of the degree of sourness of solutions or foods will be correlated with the total concentration of the protonated forms of the acids and the hydrogen ion concentration to evaluate whether our hypothesis concerning the ability of humans to perceive the intensity of sourness. Significant Activities that Support Special Target Populations This report serves to document research conducted under a USDA-CSREES- NRICGP grant no. 2003-01479. Additional details of research can be found in the report for the parent project (6645-41000-005-00D) entitled Improved Processes for Cucumbers, Cabbage, Sweetpotatoes, and Peppers to Make High-Quality, Nutritious Safe Products and Reduce Pollution. Progress was monitored by meeting and reviewing results with principle investigator and scientists carrying out research. Two manuscripts were prepared, submitted and published.
Impacts
(N/A)
Publications
- Da Conceicao Neta, E.R., Johanningsmeier, S.D., McFeeters, R.F. The Chemistry and Physiology of Sour Taste � A Review. Journal of Food Science. J. Food Sci. 72 (2):R33-R38
- Da Conceicao Neta, E.R., Johanningsmeier, S.D., Drake, M.A., McFeeters, R. F. A chemical basis for sour taste perception of acid solutions and fresh- pack dill pickles. Journal of Food Science. 72(6):S352-S359.
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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 USDA-CSREES- NRICGP grant no. 2003-01479. 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. This grant was awarded August 15, 2003, and an ARS account was established October 28, 2003. Sour taste intensity was measured by a highly trained 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.
Impacts
(N/A)
Publications
- Johanningsmeier, S.D., McFeeters, R.F. and Drake, M.A. 2005. A hypothesis for the chemical basis for perception of sour taste. Journal of Food Science. 70:R44-R48.
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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 USDA-CSREES- NRICGP grant. 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. This grant was awarded August 15, 2003, and an ARS account was established October 28, 2003. A sensory panel was recruited and rigorously trained to score the intensity of sourness, sweetness, bitterness, saltiness, and astringency on a 15- point spectrum scale. Initial experiments were done to measure the intensity of sourness with mixtures of selected organic acids adjusted to targeted protonated acid concentrations. The results suggest that pH affects sourness perception to a greater degree than would be expected by addition of the proton concentration to the
concentration of protonated acid molecules. This indicates that a separate term to account for the pH effect will need to be included in a predictive sourness model. A paper describing the background of sourness intensity research and preliminary data which served as the basis for a new hypothesis for the chemical basis of sourness perception has been prepared and submitted for journal review.
Impacts
(N/A)
Publications
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