Caramel
Amthor’s Test.—10 cc. of a solution of the fruit is put into a deep, narrow glass (a bottle may be used). Add 30 to 50 cc. of paraldehyde, to be gaged by the intensity of the coloring. Then add a sufficient quantity of absolute alcohol to make the solutions mix. If caramel is present, a brownish-yellow to dark-brown precipitate will be formed, decant, wash the precipitate once with absolute alcohol, dissolve in a little hot water and filter. The shade of color is proportional to the amount of caramel present.
To verify the test, pour the colored fluid into a freshly prepared solution of phenylhydrazin (2 parts phenylhydrazin-hydrochlorid, 3 parts sodium acetate, and 20 parts water). Much caramel produces a dark-brown precipitate in the cold, and is hastened by slightly heating. A very small amount of caramel will require several hours to precipitate.
APPLE-JUICE IN JELLIES MADE OF SMALL FRUITS
Very often cider is added to other fruit juices to give them the proper consistency in jellies, jams, and marmalades.
Its presence may some times be determined by making the usual starch test. A large quantity of starch is normally present in apples, but is less as they ripen, and finally disappears in the ripened fruit. There is no starch, or only a mere trace, in small fruits even when green. It is readily seen that if the juice is taken from green apples that there will be starch found in the artificial jelly or jam, though its absence does not prove the absence of cider.
Make the starch test as follows:
STARCH
In Jellies, Jams, and Such Products
Make a solution of the jelly or jam and destroy the color by heating nearly to the boiling point and adding dilute (1 : 3) sulfuric acid and potassium permanganate until the color is destroyed. This treatment does not affect the starch, and when cool add iodin, preferably potassium iodid-iodin (potassium iodid, 0.4 gram; iodin, 0.1 gram; water, 20 cc.). If a great quantity of starch is present an almost black precipitate will be formed. Smaller amounts give the usual blue color.