Jamaican Coffee - the finest in the world!
What is involved in going from the ripe beans, to the roasted
beans, to end up as a finished product?
Have you heard so much about synthetic as opposed to "natural"
or "organic" chemistry and are starting to wonder whether it all
happens like the right hand side of the above picture?
Then read on....
Apart from the Chemistry below, did you know that:
- it has been claimed that coffee is second to oil in terms of
world commodity trading and that it provides employment for
around 20 million people!
- the name coffee may be derived from the Arabic "qahwah" or
alternatively may have arisen due to the connection with the
province Kaffa, in Ethiopia.
- the coffee tree is indigenous to Ethiopia, not Arabia as many
tend to think and belongs to the genus Coffea of the Rubianceae,
or madder, family.
- the first English coffee house opened in Oxford in 1650 and
by 1675 there were nearly 3000 coffee houses in England.
- Johann Sebastian Bach is thought to have been a devoted coffee lover and
wrote a secular work
"The coffee cantata - Kaffe Kantate" in 1732 that includes
an aria "Mm! How sweet coffee tastes! More delicious than a thousand kisses,
sweeter by far than muscatel wine! I must have my coffee."
- seedlings produced by the Amsterdam Botanical Gardens, later
classified as Coffea arabica var arabica
account for most of the billions of trees now growing in South
and Central America and the Caribbean.
- the next most important strain of arabica (var
bourbon) came from French plantations on the Indian
Ocean island Reunion, originally called Bourbon.
- the other commercially important species, Coffea
canephora (usually referred to as robusta) is also
a native of Africa and now accounts for 20% of world
exports.
There are a number of varieties of both arabica and robusta.
In Jamaica, only arabica is grown and according to
The Jamaica Agricultural Commodities Regulatory Authority, Coffee Division
1953/1983 Regulations
"blue mountain coffee means:
coffee that is grown in the Blue Mountain Area as described in the Schedule;
and processed or manufactured at any coffee works specified in the Schedule
and to which a licence granted pursuant to regulation 5 relates."
The quality of the beans is
graded
into Blue Mountain No. 1 - 3, Pea Berry and Triage.
Other grades of Jamaican coffee include: High Mountain Supreme,
Jamaica Prime and Jamaica Select. In its wild state, the shrub grows to
about 8 to 10 metres.
Although Jamaica does not have much of the world market in terms of production
(International Coffee Organisation)
, the beans are well known for their exceptional quality and Blue Mountain coffee commands extremely
high prices. Blue Mountain Peak stands approximately 2256 m (7402 feet) high,
the average rainfall for Jamaica is about 198 cm (78 inches) and the average temperature is 27 C (82 F).
Together with sunshine every day and good soil, it all contributes to
not only great coffee but the land of "wood and water" presents an incredibly
beautiful environment to live and work in.
A brief history of Jamaican coffee from the
The Jamaica Agricultural Commodities Regulatory Authority or the
Jamaican Gleaner
It is interesting to note that coffee arabica was characterised by Linnaeus in 1753
by which time Jamaica had been growing coffee for 25 years.
Coffee Chemistry
For simplicity, this will be subdivided into sections.
- Carbohydrates
- Nitrogenous Components
- Chlorogenic Acids
- Volatile Components
- Carboxylic Acids
Carbohydrates
A range of carbohydrates, including polysaccharides and the low
molecular weight sugars (mono-, di- and trisaccharides) are found
in green coffee.
Sucrose is the major free sugar present and for arabica is
present at about 8% on a dry basis.
Polysaccharides (glycans) amount to up to 50% on a dry basis of
green coffee. Hydrolysis of coffee polysaccharides has been shown
to give mannose >> galactose > glucose >>
arabinose.
On roasting the coffee major changes occur, depending on the
degree of roasting, e.g. from light to dark and simple sugars
such as arabinose are progressively destroyed.
Nitrogenous Components
These may be described in terms of three main groups of
compounds: alkaloids, trigonelline together with nicotinic acid
and amino acids and proteins.
Caffeine.
Caffeine is perhaps the
best known and controversial alkaloid found in coffee and it is
present at about 1-2% on a dry weight basis in arabica.
An alternative view (random dot 3D
image) of the caffeine molecule can be found here.
Trigonelline
Trigonelline has received
considerable attention as a nitrogen containing component of
coffee due to its reported antitumour activity.
It is present at about 1% on a dry weight basis but it is
thermally unstable and hence can lead to other nitrogenous
materials upon roasting such as pyridines and pyrroles.
A note on the
effect
of the roasting process on the presence of trigonelline
is available on-line.
Chlorogenic Acids
Quinic acid is one of the dominant acids found in the coffee bean. It occurs
as both the free acid and as esters, mainly with caffeic acid. Immature green
coffee beans contain considerable amounts of these 5-chlorogenic
acid derivatives.
Volatile Components
The analysis of the volatile material is usually achieved by
initial separation using Gas Chromatography or HPLC. For example,
headspace analysis methods involve sampling the vapour phase
which is directly above the sample.
An indication of the diversity of the composition of roasted
coffee can be seen from the numbers given in the Table below,
which highlights the sensitivity of the GC/MS detection
method.
Flavour Constituents in Roasted Coffee
Aroma
| Type |
Number |
| furans |
99 |
| pyrazines |
79 |
| ketones |
70 |
| pyrroles |
67 |
| hydrocarbons |
50 |
| phenols |
42 |
| esters |
29 |
| aldehydes |
28 |
| thiazoles |
28 |
| oxazoles |
27 |
| thiophenes |
26 |
| amines + N-containing |
24 |
| alcohols |
20 |
| acids |
20 |
| sulfides + S-containing |
16 |
| pyridines |
13 |
| not classified |
9 |
| lactones |
8 |
| |
|
| Total |
655 |
The following sensitive map is a simulation of a GC/MS, the GC, in JCAMP-DX format, of roasted
coffee can be downloaded. It was originally created for those running Windows
who had the MDL Chime plugin installed (now obsolete) and was a very early
example of an interactive Chemistry enhanced web page. By
selecting a numbered box the Mass Spectrum (or MOL if the MS is unavailable),
was downloaded for that constituent.
More recently, alternative methods using a JCAMP-DX display of a simulated GC
either with JSpecView vs 1
and JSpecView vs 2
and Jmol have been produced as well.
Only the more intense peaks have been shown and they have been
identified as:
| Peak No. |
FEMA code |
Chemical |
| 1 |
(NA) |
2-methylfuran MOL or
MS |
| 2 |
(2170) |
2-butanone MOL or
MS |
| 3 |
(NA) |
2-methylbutanal MOL or
MS |
| 4 |
(NA) |
2,5-dimethylfuran MOL or
MS |
| 5 |
(2370) |
2,3-butanedione MOL or
MS |
| 6 |
(3523) |
pyrrolidine MOL |
| 7 |
(2841) |
2,3-pentanedione MOL or
MS |
| 8 |
(NA) |
2-methylthiophene MOL |
| 9 |
(3407) |
trans-2-methyl-2-butenal
MOL
|
| 10 |
(NA) |
4-methyl-2,3-pentanedione
MOL or
MS |
| 11 |
(NA) |
3-methyl-1-hydroxybenzene
MOL |
| 12 |
(NA) |
pyrazine MOL |
| 13 |
(NA) |
furfurylmethylether MOL |
| 14 |
(3309) |
2-methylpyrazine MOL or
MS |
| 15 |
(2170) |
2-butanol-3-one
MOL
|
| 16 |
(NA) |
1-propanol-2-one
MOL
|
| 17 |
(3272) |
2,5-dimethylpyrazine
MOL or
MS |
| 18 |
(3273) |
2,6-dimethylpyrazine
MOL or
MS |
| 19 |
(2489) |
furfural
MOL or
MS |
| 20 |
(NA) |
ethyleneglycol diacetate MOL
|
| 21 |
(NA) |
furfuryl formate
MOL
|
| 22 |
(3163) |
2-acetylfuran
MOL
|
| 23 |
(3386) |
pyrrole MOL orMS |
| 24 |
(NA) |
1-(2-furyl)-2-propanone
MOL
|
| 25 |
(2490) |
furfuryl acetate
MOL
|
| 26 |
(2702) |
5-methylfurfural MOL |
| 27 |
(2491) |
furfuryl alcohol MOL or
MS |
The numbers in the second column are the FEMA codes (Flavor and
Extract Manufacturers' Association of the USA) as found in the
Aldrich Flavors and Fragrances Catalog.
Most of these volatile compounds are derived from pyrolysis or
from reactions occurring during the roasting of the raw bean.
These reactions involving sugars, amino acids, organic acids and
the phenolic compounds give rise to the characteristic aroma and
flavour associated with the different types of coffee. The nature
of the volatile compounds and the exact composition found is
dependent on a variety of factors that include the location
during growth (eg climate and soil conditions), the storage of
the beans (both during harvesting and subsequent to roasting) and
the roasting conditions used (type of equipment, time and
temperature).
Aroma Chemistry is described at the
Coffee Research Institute site
maintained by Michael Griffin.
Carboxylic Acids
Aliphatic carboxylic acids play a large role in the quality of
coffee and coffee infusions. Changes in pH can lead to ionisation
of functional groups (eg phenolic hydroxy groups) and this can
alter the flavour of the product.
A number of acids reported to be present in coffee have
characteristic flavours and their thresholds in aqueous solution
may be as low as under 10 ppm. For example, 2-Methylvaleric acid
is reported to impart a flavour of cocoa or chocolate, whereas
pyruvic acid gives rise to a burnt caramel flavour.
In green coffee, non-volatile acids such as citric acid, malic
acid, oxalic acid and tartaric acid make up less than 2%.
In roasted coffee, over 30 aliphatic acids have been identified.
These include 15 non-volatile monocarboxylic acids C1-C10, whilst
the remainder are volatile. In general, the darker the roast, the
lower the acid content.
Acid Chemistry is described at the
Coffee Research Institute.
A list of chemicals identified in coffee seeds or leaves has been compiled
by the
USDA - ARS - NGRL, Beltsville Agricultural Research Center, Beltsville, Maryland
References:
To learn more about the chemistry of coffee, see:
"Coffee" Volume 1:Chemistry. Edited by R.J. Clarke and
R.Macrae,
Elsevier Applied Science Publishers, London and New York,
1985.
"Coffee: Recent Developments"
By: R Clarke (Consultant, Winchester, UK) and O G Vitzthum
ISBN: 0632055537, World Agriculture Series, USA, Apr 2001.
"Coffee Flavor Chemistry" by Ivon Flament,
ISBN: 0471720380, John Wiley & Sons (December 11, 2001).
"Volatile
compounds in foods and beverages" , Ed by H. Maarse, Marcel
Dekker, Inc, New York, 1991.
The proceedings from the The International Association on Coffee Science
conferences.
The Coffee Berry Borer
In 1994, the Jamaica Coffee Industry suffered losses estimated at
over J $ 70,000,000, due in part, to borer infestation. The
Coffee Berry Borer originated in East Africa and was first
reported in 1867. Its first appearance in the Caribbean was not
reported until 1971.
It appears that endosulphan, the pesticide
used to spray the shrubs, may not be as effective as once thought
and in fact, a mutant form of the insect seems to be resistant.
This new form was found in New Caledonia and has NOT yet been
seen in Jamaica.
In Jamaica, the recommended dose of endosulphan is 600-800 ml /
200 l water.
Reference:
The Gleaner, Saturday 17th February, 1996 page 4C.
Production Figures
The crop year is from 1st August to 31st July of the following
year.
|
CLEAN BEAN PRODUCT EXPORT SALES
|
|
|
Blue Mtn
|
Lowland
|
Volume
|
Value
|
|
Crop year
|
lbs
|
lbs
|
lbs
|
US $
|
|
|
|
|
|
|
1981/82
|
404,165
|
2,934,728
|
2,046,208
|
6,503,556
|
|
1987/88
|
1,263,730
|
3,225,880
|
2,970,000
|
9,245,801
|
|
1991/92
|
2,050,000
|
2,910,000
|
2,467,740
|
13,985,009
|
|
1995/96
|
2,572,250
|
1,907,211
|
3,052,535
|
24,296,347
|
In 1997, the retail price of Blue Mountain coffee in Japan
ranged from US$ 100 to $130 per kilogram compared to $20 to $40
for the blended Blue Mountain coffee. The blend is governed by
Japanese regulations and must contain at least 30% of Jamaican
coffee once the Blue Mountain name is used.
The figures show the increasing trend in production of Blue
Mountain coffee and reveal the need for more lowland coffee. The
Japanese companies are now forced to use Blue Mountain in their
blends with Colombian and Brazilian coffee due to the shortage.
References:
The Gleaner, Sunday 8th June-1997, pages 8 and 11A.
All about coffee
by WILLIAM H. UKERS, NEW YORK, THE TEA AND COFFEE TRADE JOURNAL COMPANY, 1922
The answers to some Frequently Asked Questions about coffee
and caffeine
have been collected by Alex López-Ortiz and Daniel
Owen.
The National Coffee
Association in the USA has sponsored a site to give more
information on coffee.
article on coffee from Britannica
Return to links to the chemistry of other Jamaican items, including
spices and fruit and vegetables.
Return to Chemistry, UWI-Mona,
Home Page
Copyright © 1995-2024 by Robert John
Lancashire, all rights reserved.
Created and maintained by Prof. Emeritus
Robert J. Lancashire,
The Department of Chemistry, University of the West Indies,
Mona Campus, Kingston 7, Jamaica.
Created Feb 1995. Links checked and/or last
modified 20th January 2024.
URL
http://wwwchem.uwimona.edu.jm/lectures/coffeeJS.html
