Scientists offer predictions for sour taste in acid foods

"This study provides a new understanding of the chemical species that are able to elicit sour taste and reveals a basis for predicting sour taste intensity in the formulation of acidified foods,"​ wrote the authors from the U.S. Dept. of Agriculture, Agricultural Research Service, and North Carolina State University. Taste is a key driver in the €3.2 trillion global food industry and a greater understanding of the physiology of consumers, could lead to strong market advantages. In background information in the article, lead author Edith Ramos da Conceicao Neta states: "Sour taste is influenced by pH and acids present in foods. It is not currently possible, however, to accurately predict and modify sour taste intensity in foods containing organic acids."​ In order to address this, the researchers investigated if protonated (undissociated) organic acids and hydrogen ions affect sour taste under acidic condition (pH 3.5 and 4.0). According to the Bronsted-Lowry concept of acidity, an acid is a proton donor. After donation the acid is described as dissociated. Writing in the Journal of Food Science​, Neta and co-workers report using nine trained female tasters and found that the nature of the organic acid did not affect sour taste. "All of the organic acids in each of their protonated forms were equivalent in their ability to elicit sour taste,"​ wrote the researchers. "Conclusions from these results are that all protonated organic acids are equally sour on a molar basis, that all protonated species of a given organic acid are equally sour, and that hydrogen ions and protonated organic acids are approximately equal in sour taste on a molar basis,"​ they added. Therefore, food formulators may use this method to predict the sour taste in acidified beverages by measuring the molar concentrations of these acids. It may also allow for the modification of the overall taste of the product, thereby enhancing the acceptance by consumers, the researchers concluded. Previous research into taste has revealed that the human tongue has about 10,000 taste buds with five taste sensations: sweet, bitter, and umami, which work with a signal through a G-protein coupled receptor; salty and sour which work with ion channels. Contrary to popular understanding, taste is not experienced on different parts of the tongue. Though there are small differences in sensation, which can be measured with highly specific instruments, all taste buds, essentially clusters of 50 to 100 cells, can respond to all types of taste. Taste buds (or lingual papillae) are small structures on the upper surface of the tongue that provide information about the taste of food being eaten. Source: Journal of Food Science​ (Blackwell Publishing) OnlineEarly Articles, doi:10.1111/j.1750-3841.2007.00400.x "A Chemical Basis for Sour Taste Perception of Acid Solutions and Fresh-Pack Dill Pickles" ​Authors: E.R. da Conceicao Neta, S.D. Johanningsmeier, M.A. Drake, and R.F. McFeeters