The Psychophysical Relationship Between Color and Sodium Chloride Concentrations in Model Systems

Abstract

A 10-member taste panel evaluated the effect of color on salt perception using magnitude estimation. Samples, colored to simulate commercial chicken broth were formulated by addition of increasing amounts (0.00-4.10%) of 0.05% FD&C Red 40 to a constant volume of 0.10% FD&C Yellow 5 in double-distilled deionized water. In each of four experiments, five color intensities were evaluated at five NaCl concentrations over a range of 0.14-1.06% (w/v). The Gardner XL-23 colorime-ter was used to obtain L, a and b values from which the objective color parameter log cot" 1 (a/b) was calculated. Log cot" 1 (a/b) correlated well with log color intensity and was therefore, suitable as a predictor. In all experiments, panelists were able to detect differences among the NaCl concentrations (P<0.001) regardless of color. The perception of saltiness increased with increasing salt concentration as a linear power function with slopes greater than one. Although color tended to confuse the perception of saltiness, this effect was not significant. Color is of primary importance in the initial judgement of food and ultimately aids in its acceptance or rejection. It is involved in taste recognition and taste identity (8,12,13,18), in flavor identification (2,6), in food preference (3,4,5), in pleasantness (4,9,10) and in acceptability (4,19,22) of food products. Pangborn (18) evaluated colorless, green, yellow and red solutions of 5% sucrose and concluded that sweetness discrimination was not influenced by color. However, Johnson et al. (9) found that color significantly affected sweetness perception in cherry-flavored red-colored drinks. Kostyla (77) reported that addition of blue to cherry-and strawberry-flavored drinks reduced tartness and fruit flavor by 20%, yellow decreased flavor by 3-5%, sweetness by 2% and red increased sweetness by 5-10% although the sucrose contest was the same. Qualitative studies (3,5,8,9,10) have shown that colored solutions are perceived as having a more intense flavor than colorless ones and darker solutions more intense than lighter ones. Little information is available on the influence of color on saltiness perception. Because of the increased consumer awareness of sodium in the diet and the alleged role of sodium in hypertension, an investigation of the factors which might affect sodium chloride perception is important. Therefore, this study was designed to evaluate the interaction between color and saltiness using magnitude estimation techniques. MATERIALS AND METHODS Eighteen untrained students and employees (13 females, 5 males; 22-32 years of age) in the Department of Food Science and Nutrition at the University of Massachusetts volunteered to participate in the taste panel tests. All individuals were screened for normal color vision using the Ishihara test for color blindness (7). Correct identification of all 11 tests plates was required for acceptance on the panel. A 30-min training session was provided to familiarize the panelists with the concept of magnitude estimation using a series of lines and shapes (75). A ranking test was used to determine that the panelists were able to discriminate among various NaCl concentrations (20). For each experiment 10 of the 18 panelists tasted twice a day once in the morning and again in the afternoon so that two observations per sample per panelists per day were obtained. All samples were formulated using freshly made, double-distilled deionized water (DDW), prepared using a Corning model AG-3, 220 volt, 2300 watt Still and Bantom Demineralizer model BO-5 (Barnstead Still and Sterilizer Corp; Boston, MA). The designated colors were added to the DDW at the beginning of each 6-d experiment. Twenty two hours before the taste panel session the appropriate amount of NaCl was added to each colored solution which was stored in covered glass flasks. One hour before tasting half of each sample was poured into stainless steel soup containers, covered and placed in a water-bath (Will Scientific Inc. No. 0266) set at 60°C. The remaining solutions were used in the afternoon session. Odorless white china soup bowls which had been coded with a 3-digit random number were heated in a standard household oven (105°C) for 15 min before serving. A 50-ml sample was placed in each bowl approximately 5 min before the start of the taste panel session and covered with a watch glass to provide a sampling temperature of 50°C. The reference was placed on the left side of the tray and the remaining samples were randomized for each panelist. The samples were served in individual, controlled atmosphere booths illuminated by 100 W incandescent bulbs.