Next to cellular tissue, starch is the most important element for consideration in the plant, which possesses an organized structure and is distinguished by its reaction with iodine solution, which gives it a deep blue or blackish-blue color, varying somewhat with different kinds of starch and with the strength of the reagent, and its absence is marked by no blue color under the same circumstances.
Heat, however, as in the process of baking, so alters starches, converting them into dextrine and related bodies, that they give a brown color with iodine, instead of a blue-black; they are no longer starch, however; their form, not being essentially changed, permits of their identification, with a study of the size and shape of the granules of the hilum, or central depressions of nucleus, and the prominence and position of the rings. By polarized light and selenite, the starches of tubers showed a more varied play of colors than the cereal and leguminous starches which are produced above ground. The starches we are to consider are those of a limited number to be met with in spices and their adulterants, and one must be able readily to recognize the following:
STARCH NATURAL TO SPICES AND CONDIMENTS
Ginger,
Pepper,
Nutmegs,
Cassia,
Pimento,
Cinnamon,
Cayenne.