2.2. Sour taste threshold determination The ascending method of limits (ASTM E679), as described in the ASBC Methods of Analysis (ASBC, 2007; Irwin, Bordeleau, & Barker, 1993), was used to determine the best estimate threshold (BET) of hydrogen ions and some common organic acids in water. A solution containing an appropriate concentration of target compound in water was used to spike pure water. Six sets of three glasses of water at room temperature (one with target compound and two controls) were tasted by 16 assessors. The concentration of target compound was doubled from one set to the next, and the assessor was asked to identify the pair in each triangle. The individual BETs were calculated as the geometric mean of the highest missed concentration, and the next highest. The group BET was calculated from the individual results.