Coffee
Freshness
Dr. Marco WELLINGER
Dr. Alexia GLÖSS
Dr. Samo SMRKE
Barbara EDELMANN
Chahan YERETZIAN
1
Every step matters to obtain a good cup of coffee
Why focus on
freshness ?
• Serving temperature
• Cup size and shape
• Black, with milk, sugar or other ingredients
• Water temperature, pressure, mineral content
• Extraction technique (espresso, filter, …)
• The Barista
• Particle size distribution
• Temperature of burs
• Orientation, diameter, material of burs
• Propagation & Irrigation
• Input of chemicals (fertilizers, …)
• Farm management
• Species (C. arabica, C. canephora)
• Varieties (Bourbon, Typica, …)
Brewing
Grinding
• Technology (drum, tangential, fluidized bed …)
• Roast degree / weight loss
• Time temperature profile
• Stripping, picking, mechanical harvesting
• Dry, semi-dry, wet processing
• Special PH treatments (Monsooned, Kopi Luvak)
Consumption
Roasting
Harvesting, PostHarvest Treatment
Agronomy
Genetics
2
1
The secret to great coffee is the people who make it
It All Began … when Alfred Peet opened a coffee store in Berkeley, April 1, 1966
Few noticed but a revolution was brewing. His coffee was unlike anything Americans
had ever tasted before – small batches, fresh beans, … .
His philosophy: there should be the shortest distance possible between the roaster
and the customer
Alfred Peet's inspired and guided founders of Starbucks.
3
In 1971, Jerry Baldwin, Gordon Bowker and Zev Siegl founded Starbucks in
Seattle, selling fresh-roasted whole beans to local customers
4
2
« Specialty Coffee » origin of the wording
The phrase « Specialty Coffee » was first used Erna Knutsen
by Erna Knutsen, a small Roaster, in 1974 in an
article of the Tea & Coffee Trade Journal.
The concept: special geographic microclimates
produce beans with unique flavor profiles,
which she referred to as 'specialty coffees.'
Underlying this idea of coffee appellations
was the fundamental premise that specialty
coffee beans would always be well prepared,
freshly roasted, and properly brewed.
•
•
1982: Specialty Coffee Association of America
1998: Speciality Coffee Association of Europe
5
6
3
7
8
4
Freshness is at the heart of Specialty Coffee
During roasting:
Formation of coffee aroma compounds
• Formation of CO2 (Carbon dioxide)
 Barely created they already start do evaporate and degrade
Make freshness measurable! •
N
R
N
R
OH
O
SH
R
O
R
O
SH
N
R
N
R
OH
O
R
SH
O
S
O
SH
O
O
S
O
O
R
O
S
O
R
R
O
O
S
9
(Loss of) Freshness  Make freshness visible
 Make freshness measurable
During
roasting
Aroma is generated …
and already starts degrading
CO2 is generated …
and already starts being lost
Once
roasting is
completed
Aroma starts degrading
• Evaporation
• Oxidation / chem. reactions
• Temp., humidity, light
Loss of CO2
Measure
freshness
Measure changes in
aroma compounds
during storage:
“freshness indices”
Measure degasing
during storage:
loss of CO2 and CO
10
5
Coffee aroma formation during roasting
Roasted Coffee
OH
O
Roasted Coffee
Coffee Aroma
Precursors
(Green Coffee)
C O2
HC O2H
C H3C O2H
H O C O2H
H O C O2H
C H3
SUGARS
O
Sucrose, glucose,
fructose
(arabinogalactans)
Furaneol
HO
C HO
O
HMF
+
AMINO ACIDS
(Strecker-active AA)
N
+ Pyridine and
derivatives
Nicotinic acid
HO
HO
OH
glycolic
lactic
O
R2
R
R1
O
Diketones
R3
R3
Aldehydes
N
R1
N
R2
Pyrazines
O
SH
CHLOROGENIC ACIDS
O
SH
H
O
2-Furfurylthiol
3-Mercapto-3-methylbutyl-formate
Chlorogenic acid lactones
CO 2H
OH
TRIGONELLINE
acetic
Maillard, Strecker
O
CO2 H
Formic
Quinic+acid
lactone
Caffeic + Ferulic acids
ORGANIC ACIDS
CO 2
C HO
Quinic acid
LIPIDS
R
Carbonyls
O
O
CAROTENOIDS
E- -Damascenone
O
OH
OH
Vanillin
Guaiacols
11
The aroma of coffee
 1000 volatile compounds
 5 % have odour
 25 are important coffee aroma compounds
12
6
Some important coffee aroma compounds
H2S
SH
N
OH
R
OH
O
R
CH3SH
O
R
SH
N
R
O
O
SH
O
SH
S
O
H
O
R
O
R
O
S
O
SH
OH
O
13
Chemical markers: “Freshness indices” related to coffee aroma
Ratio 1: Dimethyl disulfide / Methanethiol
CompoundsCompounds
CAS #
Odor
CAS #
2,3-Butanedione
2,3-Butanedione
431-03-8
buttery, creamy,
buttery,
fatty,
creamy,
oily, fatty, oily,
431-03-8
low
sweet, vanilla,
sweet,
caramel
vanilla, caramel
Odor
Volatility
Volatility
Reactivity Reactivity
low
low
low
Dimethyl
disulfide
Dimethyl
624-92-0
disulfide
sulphurous,sulphurous,
onion, garlic,
onion, garlic,
624-92-0
medium
burnt rubberburnt rubber
medium
high (ox.)
high (ox.)
Methanethiol
Methanethiol
74-93-1
sulphurous,sulphurous,
rotten eggs, rotten
fish, eggs, fish,
74-93-1
high
cabbage, garlic,
cabbage,
cheesygarlic, cheesy
high
very high (ox.)
very high (ox.)
2-Methylfuran
2-Methylfuran
534-22-5
burnt, ethereal,
burnt,
gasoline,
ethereal, gasoline,
534-22-5
very high
acetone, chocolate
acetone, chocolate
very
veryhigh
low
very low
Processes that lead to changes in aroma compound:
•
•
•
Evaporation
Oxidation
Other reaction / “intrinsic” reactivity
14
7
Dimethyldisulfid and Methanthiol (Medium roast degree: Pt 95)
250'000
9'000
0.6
Ratio 1:
Dimethyldisulfid / Methanthiol
8'000
0.5
7'000
5'000
4'000
100'000
3'000
0.4
Ratio 1
6'000
150'000
I (Dimethyldisulfid) * g
I (Methanthiol) * g
200'000
0.3
0.2
2'000
50'000
0.1
1'000
0
0
0
1
2
3
0
0
Storage time / weeks
1
2
3
Storage time / weeks
15
Storage of whole beans: Aluminium packaging with valve
• Ethiopian Limu, Washed, Grade 2, Arabica
• Roasted on a 1-kg batch size Probatino
• Roast degree 93 Pt (Colorette), medium roast
• 65 g roasted whole beans in each pack
• Packaging: plastic composite film with thick aluminum layer
• Valve
• Heat sealed
• Stored at 22 °C (room temperature) and at 50 °C
16
8
The evolution of the ratio dimethyl disulfide / methanethiol
stored at room temperature and at 50 °C
6
0.07
Dimethyl disulfide / Methanethiol
at 22 °C
0.06
Dimethyl disulfide / Methanethiol
at 50°C
5
0.05
Ratio
Ratio
4
0.04
3
0.03
2
0.02
1
0.01
Charge 3
Charge 4
0
0
1
2
Storage/ weeks
3
4
Charge 3
Charge 4
0
0
1
2
3
Storage/ weeks
4
5
  10-fold acceleration of degradation when going from 22 °C to 50 °C
 Very sensitive freshness index : significant changes within 1 week
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The chemistry of freshness index Dimethyl disulfide / Methanethiol
Methional
Methionine
O
NH2
H3C
OH
S
H3C
S
O
S
DMS + DMTS
H3C
CH3
H3C
SH
S
Dimethyldisulfid (DMDS)
Freshness Index 
DMDS
MeSH
Methanethiol
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9
Freshness roasted whole beans
Chemical markers
• Freshly roasted coffea arabica from Guatemala, 250 g roasted whole beans, stored at room temperature
• Packed in four different packaging materials (with valves except for paper packaging)
19
Freshness in single serve capsules (ground coffee / hermetically sealed)
Chemical markers
Code Code
C1
Del i zi o
(Ø40x26)
C2
Dol ce
Gus to
(Ø53.5x39)
C3
Denner
(Ø37x31)
C4
Nes pres s o
(Ø37x31)
Capsule
Material
· Body: PP/EVOH/PP
· Cover: PP/EVOH/PP; thi cknes s : 0.1 mm
· Ba rri er-properties i ntegra ted i nto ca ps ul e a nd cover
· Body: PP/EVOH/PP
· Cover: PP/EVOH/PP; thi cknes s : 0.12 mm
· Ba rri er-properties i ntegra ted i nto ca ps ul e a nd cover
. Extra ction s ys tem (perfora tion poi nts & a l umi num foi l ) a nd outlet for extra ct a re i ntegra ted i n cover-ma teri a l
· Body: PP (i njection mol di ng wi thout ba rri er-properties )
· Cover: Pa per wi th a l umi num coa ting; thi cknes s : 0.03 - 0.05 mm
· Secondary packaging: a l umi num; ea ch ca ps ul e i s i ndi vi dua l l y pa cked; ba rri er-properties i ntegra ted i nto
s econda ry pa cka gi ng
· Body: 99% a l umi num, wi th thi n coa ting of food-gra de s hel l a c
· Cover: a l umi num foi l ; thi cknes s 0.03 - 0.05 mm
· Ba rri er-properties i ntegra ted i nto ca ps ul e a nd cover
20
10
Freshness Index = DMDS / MeSH for Nespresso Lungo Fortissio
21
During roasting:  Drying
 Formation of CO2 (a few percent are CO)
CO2:
0 % weight,
H2O: 12
1-2
1-2
22
11
Measuring Freshness by Weighing Coffee
Physical freshness marker
VST 15 g basket filter
Probat drum roaster
Probatino
(1kg per batch)
23
The story of CO2 from green to old coffee (Arabica coffee)
Loss from
roasting to grinding
(0.15 mg/g)
Freshly roasted coffee
10
R&G
Whole beans
8
6
4
Loss from grinding
to first measurement
(0.20 mg / g)
Specific mass loss / (mg/g)
Loss during grinding
(7.6 mg / g)
2
CO2 degassing in R&G
( 2.7 mg /g)
0
0
20
40
60
80
100
120
140
160
180
200
Time / h
24
12
Weight Loss of Arabica Whole Beans
18 days
Specific mass loss / (mg/g)
12
10
10 days
8
6
Medium to dark roast
(85 Pt; Colorette)
4
18 days of degassing
2
10 mg/g corresponds
1 % weight loss
0
0
48
96
144
192 240
Time / h
288
336
384
432
25
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