The three associated beverages, cocoa, tea, and coffee are known to the French as aromatic drinks. Each of these has its characteristic aroma. The fragrance and flavor are so marked that they cannot be imitated by any artificial products, although numerous attempts have been made in regard to all three. Hence the detection of adulteration is not a difficult matter.
Designing persons, aware of the extreme difficulty of imitating these substances, have undertaken to employ lower grades, and, by manipulation, copy, as far as may be, the higher sorts. Everyone knows how readily tea, and coffee, for that matter, will take up odors and flavors from substances placed near them. This is abundantly exemplified in the country grocery or general store, where the teas and coffees share in the pervasive fragrance of the cheese and kerosene. But perhaps it is not so widely understood that some of these very teas and coffees had been artificially flavored or corrected before they reached their destination.
[source: Chocolate and Cocoa Recipes and Home Made Candy Recipes]