BSCI 124 Lecture Notes

Undergraduate Program in Plant Biology, University of Maryland


  1. Importance of trade in stimulating beverages, spices: Greater in age of discovery than now; fortunes made were comparable to today's fortunes in defense, computers, software, or cocaine.
  2. Rationale for stimulating beverages: flavor, feeling of alertness.
    Caffeine is active ingredient in the most popular stimulating beverages. Caffeine is chemically related to purine bases in DNA. See its structure.
    1. Desirable effects: Stimulation of central nervous system,. faster heartbeat,. constriction of blood vessels,. increased respiration rate, suppression of appetite (reason caffeine is in diet pills), diuresis.
    2. Undesirable effects: headaches on withdrawal, infertility, birth defects, insomnia: see coffee/caffeine heath references
    3. See what caffeine does to and for humans.
  3. Caffeine-containing drinks
    1. Coffee (Coffea arabica): Terminology about coffee
      1. A brief review of origin and history of coffee use.
        1. Native of eastern Africa; fruits and leaves eaten for stimulation.
        2. Grown in Yemen; domesticated, roasting of beans invented, 13th century.
        3. Coffee brewing spread to Arabian world in the 16th century, then spreads to Europe in the 17th century. Coffeehouses popular throughout Europe by 1700.
        4. Center of trade: Mocha, Arabia, in 17th century; Dutch East Indies and Ceylon in 18th; spread to French islands in 18th, Brazil in 19th, where it had a profound impact; now most produced in Brazil, Colombia.
        5. Additional minor species of Coffea
      2. Growing and harvesting coffee beans: see some images of coffee in Colombia
        • i. Plant is a small tree, grows in cool subtropical mountain habitats.
          ii. Small fruit is called cherry, contains two seeds called beans; harvested ripe, by hand.
      3. Processing coffee:
        1. Hull removed, seeds fermented (non-alcoholic) 12-24 hrs, dried 1 week.
        2. Coffee beans are roasted; produces flavor, dark brown color.
        3. Coffee may be decaffeinated before roasting; caffeine sold for use in medicines, soft drinks.
        4. Coffee brewed with hot water or steam.
        5. Blends & Roasts and kinds of espresso

    2. Tea (Camellia sinensis)
      1. Importance: More people drink tea than any other stimulating beverage, but international trade is less than for coffee.
      2. Origin and history of use [REQUIRED READING]: China, about 2700 BC, according to legend. Our word China derived from chai, Russian word for tea. Early to Japan; Portuguese and Dutch introduced to Europe late 1600s, after coffee. To American colonies; Boston Tea Party 1773, protest of tea tax.
      3. Cultivation and growth: Tea is a small tree, but is pruned to a bush. Youngest leaves and stem stips are harvested by hand.
      4. Processing: Green tea: leaves are steamed, rolled to break cells and release aroma, dried. Black tea: leaves are withered, rolled, fermented (non-alcoholic), dried.
      5. Aroma and flavor from essential oils, additional taste from tannins; stimulating effect from caffeine and theophylline.
      6. Caffeine levels vary with the type of tea, black most, oolong intermediate, green tea least; also length of brewing will determine the amount of caffeine in a cup of tea.

    3. Cocoa [REQUIRED READING] or cacao (Theobroma cacao) -- See archeological data here!
      1. Importance: source of cocoa for beverage and chocolate for confectionery and even known for its medicinal use
      2. Origin and history of use: used by Aztecs, who made drink of chocolate, vanilla, and chili pepper. Introduced to Spain by Cortes 1520s; Spanish added sugar. Later to rest of Europe, but not as popular as coffee or tea; greasy drink due to cocoa butter. Cocoa butter processed out 19th century, made modern cocoa. Chocolate bars also 19th century. Now grown in plantations, leading producers Singapore, Ivory Coast, Brazil.
      3. Cultivation and growth: cacao is a small tree native to South and Central American tropical forests. Fruit is size and shape of a small football, borne on trunk. Fruit harvested by hand, cut open, pulpy seeds. See this review; go down the page for cultivation, processing and chemistry
      4. Processing: Seeds fermented (non-alcoholic) 4-7 days, develops flavor and dark brown color. Seeds then are dried, polished, roasted, cracked and dehulled to release nibs (= cotyledons). Nibs are ground to paste, = chocolate liquor; molded directly for baking chocolate. Remove cocoa butter, get cocoa powder.
      5. Stimulating effect from theobromine, chemically related to caffeine.

    4. Cola drinks: from seeds of kola tree (Cola acuminata) from West Africa. Seeds fermented (non-alcoholic), dried, ground. Contains caffeine.
      1. Coca Cola: Invented 1886, extract of coca leaves and cola seeds; coca extract contained cocaine, later removed, but Coca Cola still contains rest of coca extract.

Other Sites of Interest:
Seeds of Change Garden
General coffee information
Coffee and Agriculture in the Americas
The world of tea
History of the teapot
A tour of tea preparation
Chinese tea ceremony
Japanese tea ceremony
Mexican chocolate: The original stuff
"Where chocolate grows on trees" by Carby Kummer; from The Atlantic Monthly
"Chocolate assignment" by Kate: A good review!
McCormick Spice Chart
The following treatments were prepared by James A. Duke