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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

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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)

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2

4

6

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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

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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