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Food Color

Flavor gets a lot of attention from food product designers, but color often doesn't get the attention it deserves. For fresh fruits and vegetables, for example, color is an indication of taste and flavor quality (e.g., freshness, over-ripeness or under-ripeness), and it is usually the primary attribute consumers consider in making purchasing decisions. Color measurements are useful for grading commodities.

The association of certain colors with the acceptance of specific types of foods begins early in childhood development and is maintained throughout life. The blue-green mold on bread and the off-color of meats, fruits and vegetables are warning signals that the food may be microbiologically contaminated, or at least contain off-flavors.

Fruit and vegetable processors often base decisions to harvest on color measurements. Furthermore, measuring the color of various parts of the plant may provide information that allows farmers to optimize applications of fertilizers and herbicides.

Meat processors also use color measurements to assess the quality of their products. Measuring the extent of red and brown is a good indicator of meat freshness, as well as consumer appeal and acceptance.

Measuring the color of processed foods can be a critical quality control tool. For example, the color of extruded cereal and snack products is a good indication of over- and under-processing conditions. Also, color measurements can be a useful indicator of the quality of incoming raw materials and ingredients used to prepare processed foods.

"All animals eat, but humans feed," says Fergus M. Clydesdale, Ph.D., professor and department head, Department of Food Science, University of Massachusetts, Amherst. "Eating is a festive occasion, and color adds to the enjoyment of food."

Color can dramatically influence the flavor perception of food. Food technologists often use various colored lights in their tasting sessions to mask the color of the foods being taste-paneled so tasters will make their acceptability judgments based on flavor rather than color. One study dramatically illustrates the influence of color on food acceptability (J. Wheately, "Putting Color into Marketing," Marketing, October 26, 1973). In this study, panelists were offered a dinner of steak, peas and french fries abnormally colored but served under color-masked conditions. Panelists enjoyed the meals until normal lights were switched on. The appearance of blue steak, red peas and green french fries was so overwhelmingly objectionable to some of the panelists that they became ill.

According to Clydesdale, studies show that when red color of fruit-flavored products is enhanced, the perceived sweetness level increases. Food product designers could potentially reduce sugar and calorie levels in fruit-flavored products without reducing perceived sweetness by increasing the level of red color in these products. This phenomenon has been observed in strawberry- and cherry-flavored beverages containing various levels of red color. Other colors also have been observed to affect sweetness perception, depending on the appropriate combination of color, flavor and sucrose.

In addition, Clydesdale (in "Color as a Factor in Food Choice," Critical Reviews in Food Science and Nutrition, 33(1): 83-101, 1993) reports that color affects taste thresholds. Studies indicate that the threshold concentrations at which the basic tastes (salt, sour, bitter and sweet) are perceived are color dependent. In the study, the effects of red, green and yellow on the threshold concentrations of sweet, sour, salty and bitter tastes were measured. The yellow-colored sweet solution was detected at a significantly higher concentration than the colorless control. Therefore, tasters did not associate yellow color with a sweet taste. However, the green-colored sweet solution was detectable at a concentration significantly below that of the control.

With sour solutions, the red-colored sour solution was detected at a slightly higher concentration than the colorless control sour solution. However, the sour flavor in yellow and green solutions was detected at significantly higher concentrations than in the control.

With salt solutions, color had little influence on the perception of saltiness. However, with the bitter solutions, yellow and green solutions were detected at significantly higher concentration than the colorless bitter control, but the red bitter solutions required the highest concentrations before they were detected.

One potentially useful application of color manipulation is with foods for the elderly. After age 40 the senses of smell and taste tend to deteriorate. Clydesdale says that paying more attention to color can help food processors compensate for the loss of taste perception and significantly improve the appeal of foods to the elderly. Food processors' interest in this area of color application is likely to escalate since the average age of consumers is rapidly increasing as the massive baby boom generation ages. Clydesdale has recently initiated a study to determine if color affects mouthfeel perception of foods.