Everyday millions of people around the

world begin their day religiously with a

morning cup of coffee. Though today we

can easily identify coffee in its beverage

form, it wasn’t always this way in the be-

ginning. Throughout history, coffee has

taken on several physical transformations,

initially serving as an energy source when

nomadic tribes combined coffee berries

with animal fat as an early form of an en-

ergy bar. Later it was consumed as a tea,

then a wine, and finally to the beverage

we’ve come to appreciate today. But how

much of coffee’s chemical composition do

we actually know? Over the past half cen-

tury scientists have made significant pro-

gress which has allowed them to unlock

the nearly 1,000 compounds found in

roasted coffee.

In this issue of Coffee Science we’ll briefly

discuss a family of compounds called

‘alkaloids’ which serve an important role

in coffee’s unique chemical composition.

JANUARY / FEBRUARY ‘14

UNLOCKING COFFEE’S CHEMICAL COMPOSITIONBY JOSEPH A. RIVERA, DIRECTOR OF SCIENCE & TECHNOLOGY

PART I

CAFFEINE

For many, drinking coffee is simply a de-

livery medium for a potent alkaloid we

have come to identify as caffeine or other-

wise known as 1,3,7 – trimethylxanthine.

Although caffeine is typically associated

with coffee, its production within the

plant kingdom spans across numerous

other species. Mate, for example, which is

traditionally consumed in parts of Uru-

guay and Argentina, contains less than one

percent by weight. Whereas, teas of Ca-

mellia sinesis species which originated

from China contain almost 3x times the

concentration of caffeine than coffee.

But for humans caffeine is very unique.

Thus far we are the only living forms on

Earth that readily seek caffeine for both its

stimulatory and physiological effects. ForCO

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all other life forms, caffeine is a potent

toxin capable of sterilization, phytotoxicity

and antifungal properties. As such scien-

tists believe that caffeine, with its intensely

bitter taste, has evolved as a primitive de-

fense mechanism in coffee ensuring its sur-

vival in the wild for thousands of years. It’s

no surprise then, that the caffeine content

of the more “robust” Robusta species is al-

most double that of the more delicate Ara-

bica. The belief is that as insects attack the

coffee cherry, they are deterred by the bit-

ter taste of caffeine and simply move on to

other crops.

TRIGONELLINE

Another less known alkaloid that shadows

in the light of caffeine is that of trigonelline.

In Arabica coffee, trigonelline concentra-

tions make up roughly 1% by weight with

a slightly less concentration (0.7%) found

its Robusta counterpart. Although its con-

centration is slightly less than that of caf-

feine, it plays a significant role in the de-

velopment of important flavor compounds

during roasting. But unlike caffeine which

survives the roasting process, trigonelline

readily decomposes as temperatures ap-

proach 160oC (320oF). Model studies have

shown that at 160oC, sixty percent of the

initial trigonelline is decomposed, leading

for the formation of carbon dioxide, water

and the development of a large class of

aromatic compounds called pyridines.

These heterocyclic compounds play an

important role in flavor and are responsi-

ble the sweet/caramel/earthy-like aromas

commonly found in coffee.

Plant Country of Origin Caffeine Content (% wt)

Coffee bean

Coffea Arabica Ethiopia ~ 1.2%

Coffea Robusta Arabia ~2.2%

Tea

Camellia Sinesis China ~3.5%

Mate Uruguay, Paraguay, Argentina less than 0.7%

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CAFFEINE CONTENT IN VARIOUS PLANTS

Joseph A. Rivera holds a degree in food chemistry and was formerly the Director of Science & Technol-

ogy at the Specialty Coffee Association of America (SCAA). He’s the founder/creator of science portal

coffeechemistry.com and the Coffee Science Certificate (CSC) program. He can be reached at

jrivera@coffeechemistry.com

The Coffee Science Certificate (CSC) is the industry’s first and only

training program focused on coffee science. For more information see

visit coffeechemistry.com and ‘explore the chemistry in your cup’!

Another important byproduct produced

during the decomposition of trigonelline is

nicotinic acid, or vitamin B3 - more com-

monly known as niacin. Depending on

roasting conditions niacin can increase up

to ten times its initial concentration, pro-

viding anywhere between 1mg of niacin

per cup for Americano coffees and roughly

two to three times this concentration in

espresso type beverages. When one con-

siders that most Americans consume about

3.2 cups of coffee per day according to the

NCA – it makes coffee an ample source of

dietary niacin.

So far that’s great news for people with an

unbalanced diet but there is another thera-

peutic benefit to coffee that is even more

surprising. Recently Italian scientists dis-

covered that drinking coffee may lower our

incidence of dental caries. According to re-

searchers trigonelline works by preventing

the adhesion of mucus-like acid byproducts

onto teeth which would otherwise lead to

dental deterioration.

In the end, it looks like drinking a cup of

coffee may not only keeps the doctor away,

but the dentist too.

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