948 21 Coffee, Tea, Cocoa
(21.4)Table 21.13.Bitter quinic acid lactones in a decaf-
feinated coffee drinka
No. Quinic acid lactone Thresholdc Concen-
(quinides)b tration
(mg/l)I 3-O-Caffeoyl-γ-13. 433. 15
II 4-O-Caffeoyl-γ-12. 119. 68
III 4-O-Caffeoyl-muco-γ-11. 28. 27
IV 5-O-Caffeoyl-muco-γ-9. 76. 12
V 5-O-Caffeoyl-epi-δ-60. 53. 28
VI 3-O-Feruloyl-γ-13. 76. 75
VII 4-O-Feruloyl-γ-13. 73. 03
VIII 3,4-Dicaffeoyl-γ-4. 95. 40
IX 4,5-Dicaffeoyl-muco-γ-4. 91. 65
X 3,5-Dicaffeoyl-epi-δ-24. 90. 80
aMade by the percolation of coffee powder (54 g) with
water (80◦C, 1.1l).
bThe structures of the lactones I, III and V are pre-
sented in Formula 21.4.
cThreshold for the bitter taste.
21.1.4 Coffee Products
The coffee products which will be discussed are
instant coffee, decaffeinated coffee and those
containing additives.
21.1.4.1 Instant Coffee
Instant (soluble) coffee is obtained by the ex-
traction of roasted coffee. The first technically
sound process was developed byMorgenthaler
in Switzerland in 1938. Ground coffee is batch-
wise extracted under pressure in percolator batter-
ies or continuously in extractors. The water tem-
perature may be as high as 200◦C while the tem-
perature of the extract leaving the last extraction
cell is 40–80◦C. The extracts exhibit a concen-
tration of ca. 15% and are evaporated in vacuum
film evaporators to a solids content of 35–70%.
To minimize aroma losses, the extraction can be
conducted in two stages. In a gentle stage, the first
extract is obtained with a solids content of 25–
27% and carries the main portion of the aroma.
Without concentration, it is mixed with a second
extract which was obtained under stronger con-
ditions and concentrated. In addition, aroma con-
centrates can be isolated by stripping; they can be
added back before or after drying. The technical
extraction yields are 36–46%. Further process-
ing involves spray or freeze drying. In the latter
method, the liquid extract is foamed and frozen
in a stream of cold air or an inert gas (− 40 ◦C),
then granulated (grain size of 2–3 mm), sifted and
dried in vacuum in the frozen state. Spray-dried
coffee extract can be agglomerated in vibration
fluid beds by steam or spray.
The resultant extract powder is hygroscopic and
unstable. It is packaged in glass jars, vacuum
packed in cans, aluminum foil-lined bags, flexi-
ble polyethylene, laminated pouches or bags, or
packaged in air-tight plastic beakers or mugs, of-
ten under vacuum or under an inert gas.
Like roasted coffee, instant coffee is marketed
in different varieties, e. g., regular roasted or as
a dark, strongly-roasted espresso, or caffeine free.
Instant coffee contains 1.0–6.0% moisture. The
dry matter consists of 7.6–14.6% minerals, 3.2–