Experimental cookery

Color changes of fruit juices. Pratt and Swartout state that the solu- tions of many fruit pigments act as indicators; that the solutions are easily prepared and stable; that the liquid indicators can be used in titrating acids, but not bases, for in a solution no more than moderately alkaline they soon decompose, all of them producing a brown color which does not change when acid is added. They found that apricots, peaches, pears, per- simmons, and tomatoes failed to yield pigments that could be used as in- dicators. It is interesting that the pigment of cactus holds its red color even in a distinctly alkaline medium. They also state that "the pigment of red beets remained red through the acid range and into the alkaline range at least as far as /»H 13.0." In their conclusion they recommend that the greatest usefulness of the indicators is in test papers. ANTHOCYANINS 117 CI ho/ \/ ' \ C-OH OH pelargonidin chloride a / ./■ ,/" ■\ OH H C-OH \ /\ v/ v OH H cyaninidin chloride CI HO /■ ./ ./ Os \ ./■■ ./-" "V OH OH -OH \c/ OH delphinidin chloride Fruit colors and punch. Combinations of fruit juices for punch can yield beautiful, clear colors, or ugly, muddy ones. If a red color is desired, use red- or blue-colored juices and keep the reaction acid by the addition of lemon juice. For a purple shade, choose fruit juices nearly neutral in reaction and do not add lemon juice. A blue color can usually be intensified by the addition of canned pineapple juice. (See the following paragraph.) Alkaline water may or may not give a bluish tinge to red fruit juices, depending on the alkalinity of the water and the acidity of the juice. Orange FRUITS AND VEGETABLES TABLE 16 The pH Range with Color Changes of Fruit Juices {Pratt and Szvartout) Fruit source Color change pH range Apples Red to yellowish-green 6.2- 7.2 Blackberries Red to dark grayish-blue 6.0- 7.4 Blueberries Reddish-purple to greenish-purple 6.2- 7.2 Cactus Red to faint purple 9.0-12.0 Cactus Faint purple to reddish-brown 12.0-13.0 Cherries Red to bluish-purple 6.0- 7.2 Grapes Red to purple 5.0- 6.6 Grapes Purple to green 6.6- 7.6 Plums Red to yellow^ish-green 6.2- 7.2 Pomegranates Red to purple 6.0- 6.8 Pomegranates Purple to green 6.8- 7.6 Strawberries Red to yellowish-green 6.2- 7.2 TABLE 17 The Color of Fruit Juices in Neutral, Acid, and Alkaline Mediums {Pratt and Szvartout) Fruit source Neutral tint Acid tint Alkaline tint Apples Grayish-purple Red Green Blackberries Purple Red Bluish-green Blueberries Purple Red Blue Cherries Reddish-purple Red Bluish-green Cranberries Faint purple Red Light green Grapes Purple Red Bluish-green Plums Faint purple Red Light green Pomegranates Purple Red Bluish-green Strawberries Reddish-purple Red Light green juice should be added to red or blue fruit juices only when a brownish or magenta shade is desired, for often this combination is not attractive. From the colors produced, or unless very small proportions of one color are used, the red and yellow, blue and yellow, or green and yellow com- binations should be avoided.