Plants & Human Affairs (BIOL106) - Stephen G. Saupe, Ph.D.; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe |
Beverage
Botany
I. Introduction
Do you stumble
out of bed and immediately reach for a cup of coffee or tea? If so, youre not alone. Millions of people around the world start their
day with a cup of coffee. This class takes a
look at some of our important, non-alcoholic beverages.
II. The
importance of plants
Virtually all
of our culturally-important beverages, with the exception of milk, are derived from
plants. Although many plants are used to
prepare beverages, few are of major significance.
III. Preparation of beverages
Two main
techniques are used to prepare non-alcoholic beverages:
Juice - the plant material, usually a fruit, is pressed or
chopped to release the juice. Except for a
sterilization stage, the resultant beverage usually undergoes no additional processing. Examples include the juices of apple, cranberry,
citrus, pineapple, tomato, and carrots; and
Decoctions - the plant material,
typically leaves, is steeped in water.
After
a suitable period the liquid extract is separated from the spent plant materials. In many cases the plant material undergoes
considerable processing before it is ready for extraction.
Coffee, tea, and mate are good examples of decoctions.
IV. Biologically activity
All of our
commercially important beverages are biodynamic. In
other words, they exert a physiological influence on our body. For example, many are caffeinated (e.g., coffee, tea, chocolate, mate), but only a few
are not (e.g., fruit juices). The former is by far the most commercially
important type. Alcohol is a depressant of
the central nervous system. In contrast,
caffeine is a stimulant. Among its
actions, caffeine stimulates heart rate, increases acidity in the stomach, increases
metabolic rate, and mimics the effects of adrenaline.
V. Coffee
A. Taxonomy
The word coffee
is derived from the Arabic word, kahwah, which refers to the bitterness of the
beverage. Coffee belongs to the Coffee (or
Madder) Family, Rubiaceae. There are 3 major
species, Coffea arabica; C. canephora (robusta); and C. liberica. C. arabica is the most important species and
accounts for at least 80% of world trade.
B. Origin
Coffee is
originally native to Ethiopia (mountainous regions of the southwest).
C. Growth Conditions
Coffee prefers
cool temperatures and adequate moisture (ca 60
inch/year). It grows well in the American
tropics (Brazil, Columbia, Central America) and Africa.
The environment is important for flavor.
For example, Jamaican Blue Mountain has a reputation for high quality. As a generalization, the quality of coffee is:
Central America > Columbia & Jamaica > Brazil > Africa.
Coffee in Central America was traditionally grown in shade, under other
trees (nurse trees). In fact, traditional
plantations look similar to the native rainforest. This
provided habitat for birds and other wildlife. Newer,
sun-loving varieties of coffee are much higher-yielding than the shade coffees which means
that the nurse trees have been removed and the complexity of the forest system has
declined. One adverse effect has been a
decrease in our local birds that overwinter in central America. Peace coffee is a shade coffee that is
being marketed to address this situation.
D. Comparison of species
Comparison of C. canephora (Robusta coffee) and C. arabica (Arabica
coffee) |
||
Feature |
Robusta |
Arabica |
Area cultivated |
Western Africa |
Columbia, Central
America |
Volume of World
Trade |
10% |
90% |
Plant size |
Large, robust |
Smaller |
yield |
high |
Low |
Flavor |
harsher |
Mild, more
delicate |
Use |
Instants, decafs,
blends |
Fine sipping
coffees |
Pollination |
Self-incompatible |
Self-compatible |
Crop production |
2 3
crops/yr |
1 1.5
crops/year |
E. Coffee Anatomy
The seeds,
called "beans", are used to prepare coffee.
The beans develop inside a berry, called a cherry. The cherries, each of which has 2 seeds, are
harvested by hand, because they ripen non-synchronously.
This is a very labor-intensive process.
F. Coffee preparation
Cherries are
picked. The layers surrounding the seeds are
removed by:
Dry method - older, traditional method, common in Africa
where water is scarce. The dry cherries � mechanically abraded to remove
layers. This process is usually considered to
produce an inferior product and is used in Indonesian and some Ethiopian coffees.
Wet method
(Columbian, Costa Rican, Guatemalan, Kenyan, Mexican, Kona coffees): berries in water
→
ripe berry
floats, debris & unripe material sink
→
pulping
machine frees seeds from pulp
→
controlled
fermentation, 12-24 hour, chemical reactions removes remaining pulp, mucilage, etc.
→
wash
→
dry
→
mechanical
remove of endocarp in special mills
→
seed coat
(silvery skin) removed by polishing
→
sized, graded
→ roasted
G. Roasting
Brings out the
flavors, develops the aromas, and releases the essential oils by breaking cell walls. The temperature and length of roasting determines
the ultimate flavor. Dark roasts are heated
longer and to a higher temperature than light roasts.
Roasting degrees: cinnamon
roast < American roast < Full City (dk brown, no oils) < Vienna < French <
Italian. Thus, French roast is a darker, more
oily bean than, say the American roast.
H. Coffee Rust - (Hemileia)
This is a
fungal pathogen of coffee plants. Arabica
plants are susceptible. This disease has had
a major impact on coffee growing. For
example, Sri Lanka was once a major coffee producer but this fungus wiped out the
plantations. The net result is that tea was
substituted, and it fueled the British love of tea.
Robusta coffees are resistant to the fungus and are typically grown in
areas (i.e., Old World) where the disease occurs
primarily in areas where no rust.
I. History
Coffee has had
a rapid rise in popularity. It was little
used 2 centuries ago. Now it is an important
beverage for 1/3 of the world's population. Coffee
passed from Ethiopia
→ Yemen
→ Arabia
→ Syria, Turkey,
Egypt by 1500's
→ Europe by
1600's
→ Dutch
established plantations in Ceylon (Sri Lanka) / Java in East Indies
→ 1723 to New
World (Gabriel Mathiew de Clieu brought plants to Martinique).
J.
Decaffeinated Coffee
Arabica beans
are typically about 1% caffeine by weight, but Robusta beans have twice that amount. The caffeine can be removed from the bean by a
variety of methods:
Hot water extraction - this removes the caffeine, but lots of other goodies. The liquid is then extracted with methylene
chloride (or ethyl acetate) to remove the caffeine.
The
solvent is evaporated and the remaining materials are reunited with beans; and
Water process - this is similar to the process above, but the caffeine is removed from
the extract by passage through activated charcoal/carbon filters. The remaining extract is added back to beans.
K. Instant coffee.
Beans
→
brewed under
pressure (seal in flavor)
→
add aromas as
necessary
→
freeze dry or
spray nozzles from tall tower, dries as it falls.
VI. Tea
-
more people drink tea than coffee, but tea has less global commercial
importance.
A. Taxonomy
Belongs to the
Tea family (Theaceae). Tea is an evergreen
tree in the genus Camellia, or Thea according to some botanists. There are three commercially important species: C. sinensis
- low growing, China; C. assamica - high yielding, India, Sri Lanka; and C.
cambodensis - less important
B. Origin
Tea is native
to SW China and NE India to Cambodia
C. Growth
Tea prefers a
warm climate.
D. Harvest
By hand,
usually by women and children who wear a basket on their back. The tip of the twigs with 2 leaves is broken off.
E. Types of tea:
Green tea. Leaves harvested and dried immediately
→
leaves are
rolled
→ further drying. Some familiar examples are Gunpowder and Imperial
Hyssom teas.
Black tea
(fermented, preferred drink)
→
leaves are
withered (indoors on ventilated racks. This
step makes it easier to break the leaf cells and extract chemicals like polyphenols) → roller machine
crushes cells
→
frees juices,
allows enzymes (oxidases) to oxidize polyphenols
→
fermentation
rooms (allows for development of color and aroma; several hours
→
fired (heating
reduces the water content)
→
is moved on
conveyers through hot air chambers
→
turns black
→ sifted and
sorted and packed. This comprises about
78% of worlds tea and is most familiar tea type in north America.
Oolong tea - this
is a semi-fermented tea. The leaves undergo
a preliminary sun drying and are then rolled. This
type is particularly common in Taiwan and S. China.
F. Tea quality.
Depends on
cultivation, processing, environment (rainfall, elevation).
Tannins provide body (color and pungency).
Recent research
has shown that tea has anti-cancer properties. One
of its constituents, epigallocatechin gallate inhibits the formation of free radicals,
that can cause cancer.
VII. Cocao - Chocolate
A. Taxonomy
Cocao is derived from the chocolate tree (Theobroma cacao), which belongs to the family
Sterculiaceae. The scientific name, which
literally translates as god food, was
given to the plant by Linnaeus in 1753. The
word chocolate is derived from the Mayan words for plant - Coahuatl; and drink
- Xochatl.
B. Origin
The native home of the chocolate tree is the Amazon basin (i.e., eastern Andes).
C. Growth
Cocao is now grown in Central America, S. Mexico, N. South America, and
Africa (Ghana, Nigeria, Ivory Coast). In
fact, the over one third of the world crop grown in Africa.
Cocao grows best in wet tropical regions within 17 degrees of the equator.
D. Some history
Chocolate was originally drunk. Roasted
beans were put in earthenware pots, ground up to a paste with water and spices and then
whipped into a frothy consistency. Spaniards
introduced the drink in sweetened form to Europe. In
fact, Columbus brought it back to Spain on his 2nd voyage, but it wasnt until Cortez
returned to Spain in 1528 that chocolate became popular.
E. Botany
Cocao is a small understory tree.
The tree produces seeds in football shaped fruits that are attached directly
to the trunk (stem) of the tree. Each pod,
which as a hard melon-like rind and a mucilaginous inner layer, has 30-50 seeds. There are about 20-50 pods per tree. It takes about 50 seeds to make ca 100 g chocolate bar.
Other components in the seeds include:
50% cocoa butter; 15% starch; 15% protein; 3% theobromine; and a trace of
caffeine.
F. Processing
Pods harvested
→
opened with
machete
→
seeds scooped out (the pulp is sweet and can be eaten, though some are allergic
to it)
→
the seeds are
fermented in piles (the fermentation is carried out by the naturally occurring bacteria
and fungi) for 5-7 days
→
chemical
changes→
develop flavors
(and frees seeds from pulp)
→
kernel changes
from tan to purplish
→
kernel is dried
→
transported to
point of manufacture
→
seeds cleaned
→
roasted to
develop flavor
→
shelled
(remove seed coat): (a) The shells are
mulched or extracted for theobromine) → (b) nibs
(cotyledons)
→
ground to paste
(heats up and melts)
→ chocolate
liquor can be molded for baking squares (or expressed to release cocao butter and cocoa
powder, drinking chocolate). The cocoa butter
can be mixed with chocolate liquor, sugar, and with or without milk, ground further (and
agitated, called conching) for several days at 130-200 F to remove acidic and astringent
flavors that develop during roasting. The
chocolate powder is often dutched - treated with alkali to improve the flavor. The cocoa butter is mixed with the chocolate
liquor and milk sugar to make chocolate.
VII. Mate (Ilex
paraguariensis)
Mate is in the
Holly family, the Aquifoliaceae. It is native to south America - Paraguay,
Argentina, and Brazil. The leaves are dried,
crushed, are made into a tea. Mate is
traditionally prepared in gourds (a mate) and the resulting infusion is drunk through a
silver straw (bombilla).
Last updated: 12/10/2008 � Copyright by SG Saupe