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Coffee
Freshness
Dr. Marco WELLINGER Dr. Alexia GLÖSS Dr. Samo SMRKE Barbara EDELMANN Chahan YERETZIAN
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Genetics
Agronomy
Harvesting, Post-Harvest Treatment
Roasting
Grinding
Brewing
Consumption
• 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
• 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)
• Propagation & Irrigation • Input of chemicals (fertilizers, …) • Farm management
• Species (C. arabica, C. canephora) • Varieties (Bourbon, Typica, …)
Every step matters to obtain a good cup of coffee
Why focus on freshness ?
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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.
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In 1971, Jerry Baldwin, Gordon Bowker and Zev Siegl founded Starbucks in
Seattle, selling fresh-roasted whole beans to local customers
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The phrase « Specialty Coffee » was first used 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.
Erna Knutsen
« Specialty Coffee » origin of the wording
• 1982: Specialty Coffee Association of America
• 1998: Speciality Coffee Association of Europe
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Freshness is at the heart of Specialty Coffee
OSH
S O
O
SH
N
N R
RR
OH
O
R
O
R
O
O
S
During roasting: • Formation of coffee aroma compounds • Formation of CO2 (Carbon dioxide) Barely created they already start do evaporate and degrade
OSH
S O
O
SH
N
N R
RR
OH
O
RO
R
O
O
S
Make freshness measurable!
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(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
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Coffee aroma formation during roasting
AMINO ACIDS (Strecker-active AA)
SUGARS Sucrose, glucose,
fructose
(arabinogalactans)
CHLOROGENIC ACIDS
HMF Maillard, Strecker
Aldehydes Diketones Pyrazines Pyridine and derivatives
Nicotinic acid
Caffeic
Guaiacols
+
O
O H O
Vanillin
R
O O H
N
N
R 1
R 2 R 3
O
O
R
O
O
H
S H
CAROTENOIDS
O
E- -Damascenone
Ferulic acids +
3-Mercapto-3-methyl- butyl-formate
O S H
O C H O
H O
2-Furfurylthiol
Furaneol
ORGANIC ACIDS CO 2
LIPIDS Carbonyls
TRIGONELLINE
Coffee Aroma Precursors
(Green Coffee)
C H O
O O H
C O 2 H H O C H 3
H C O 2 H C H 3 C O 2 H
C O 2
C O 2 H H O
Formic
acetic
glycolic
lactic
O
R 2
R 3
R 1
Chlorogenic acid lactones
Quinic acid
CO H
OH
H O
H O O H
2
CO H
N
2 +
Quinic acid lactone
+
Roasted Coffee Roasted Coffee
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1000 volatile compounds
5 % have odour
25 are important coffee aroma compounds
The aroma of coffee
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Some important coffee aroma compounds
OSH
SH
SH
O H
O
S O
O
SH
CH3SH
H2S SH
OH
S
N
N R
RR
OH
O
R
OR
OHOO
O
R
O
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Chemical markers: “Freshness indices” related to coffee aroma
Ratio 1: Dimethyl disulfide / Methanethiol
Processes that lead to changes in aroma compound: • Evaporation • Oxidation • Other reaction / “intrinsic” reactivity
Compounds CAS # Odor Volatility Reactivity
2,3-Butanedione 431-03-8 buttery, creamy, fatty, oily, sweet, vanilla, caramel
low low
Dimethyl disulfide
624-92-0 sulphurous, onion, garlic, burnt rubber
medium high (ox.)
Methanethiol 74-93-1 sulphurous, rotten eggs, fish, cabbage, garlic, cheesy
high very high (ox.)
2-Methylfuran 534-22-5 burnt, ethereal, gasoline, acetone, chocolate
very high very low
Compounds CAS # Odor Volatility Reactivity
2,3-Butanedione 431-03-8 buttery, creamy, fatty, oily, sweet, vanilla, caramel
low low
Dimethyl disulfide
624-92-0 sulphurous, onion, garlic, burnt rubber
medium high (ox.)
Methanethiol 74-93-1 sulphurous, rotten eggs, fish, cabbage, garlic, cheesy
high very high (ox.)
2-Methylfuran 534-22-5 burnt, ethereal, gasoline, acetone, chocolate
very high very low
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Dimethyldisulfid and Methanthiol (Medium roast degree: Pt 95)
0
1'000
2'000
3'000
4'000
5'000
6'000
7'000
8'000
9'000
0
50'000
100'000
150'000
200'000
250'000
0 1 2 3
I (D
ime
thyld
isu
lfid
) *
g
I (M
eth
an
thio
l) *
g
Storage time / weeks
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 2 3
Ra
tio
1
Storage time / weeks
Ratio 1: Dimethyldisulfid / Methanthiol
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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
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The evolution of the ratio dimethyl disulfide / methanethiol
stored at room temperature and at 50 °C
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0 1 2 3 4
Rati
o
Storage/ weeks
Dimethyl disulfide / Methanethiol at 22 °C
Charge 3
Charge 40
1
2
3
4
5
6
0 1 2 3 4 5
Rati
o
Storage/ weeks
Dimethyl disulfide / Methanethiol at 50°C
Charge 3
Charge 4
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
CH3
S
NH2
O
OH
CH3 S
O
CH3 SH
CH3
S
S
CH3
Methionine Methional
Dimethyldisulfid (DMDS) Methanethiol
DMS + DMTS Freshness IndDMD
Hex
S
MeS
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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)
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Freshness in single serve capsules (ground coffee / hermetically sealed)
Chemical markers
Code Code Capsule Material
· Body: PP/EVOH/PP
· Cover: PP/EVOH/PP; thickness : 0.1 mm
· Barrier-properties integrated into capsule and cover
· Body: PP/EVOH/PP
· Cover: PP/EVOH/PP; thickness : 0.12 mm
· Barrier-properties integrated into capsule and cover
. Extraction system (perforation points & a luminum foi l ) and outlet for extract are integrated in cover-materia l
· Body: PP (injection molding without barrier-properties )
· Cover: Paper with a luminum coating; thickness : 0.03 - 0.05 mm
· Secondary packaging: a luminum; each capsule i s individual ly packed; barrier-properties integrated into
secondary packaging
· Body: 99% a luminum, with thin coating of food-grade shel lac
· Cover: a luminum foi l ; thickness 0.03 - 0.05 mm
· Barrier-properties integrated into capsule and cover
C1
C2
C3
C4
Del izio
(Ø40x26)
Dolce
Gusto
(Ø53.5x39)
Denner
(Ø37x31)
Nespresso
(Ø37x31)
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Freshness Index = DMDS / MeSH for Nespresso Lungo Fortissio
22 22
CO2: 0 % weight, 1-2
H2O: 12 1-2
During roasting: Drying
Formation of CO2 (a few percent are CO)
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Measuring Freshness by Weighing Coffee Physical freshness marker
Probat drum roaster Probatino (1kg per batch)
VST 15 g basket filter
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The story of CO2 from green to old coffee (Arabica coffee)
0
2
4
6
8
10
0 20 40 60 80 100 120 140 160 180 200
R&G
Whole beans
Specific
mass lo
ss / (m
g/g
)
Time / h
Loss from
roasting to grinding
(0.15 mg/g)
Loss during grinding
(7.6 mg / g)
Loss from grinding
to first measurement
(0.20 mg / g)
CO2 degassing in R&G
( 2.7 mg /g)
Freshly roasted coffee
13
25 25
Weight Loss of Arabica Whole Beans
0
2
4
6
8
10
12
0 48 96 144 192 240 288 336 384 432
Time / h
Sp
ec
ific
ma
ss
lo
ss
/ (
mg
/g) 10 days
18 days
Medium to dark roast (85 Pt; Colorette) 18 days of degassing 10 mg/g corresponds 1 % weight loss
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