23/11/2014

THE KINETICS OF COFFEE AROMA EXTRACTION

Frédéric Mestdagh, Britta Folmer, Tomas Davidek, Imre Blank

P2

Outline

INTRODUCTION Experimental setup

Quantitative aroma analysis in-cup

EXTRACTION KINETICS Role of odorant polarity and volatility

Impact of granulometry

CONCLUSIONS

01

02

03

From blend creation to the cup. But how about the extraction kinetics?

BLEND CREATION

Selection

Roast degree

Grind size

Capsule load

P3

EXTRACTION

Temperature

Flowtime

Water quality

Pressure

IN CUP QUALITY

Sensory attributes

Aroma composition

Non-volatile analysis

Extraction kinetics:

How are coffee odorants extracted?

Experimental setup

Modified extraction machine With pressure-programmable pump

Operating at constant pressure (20 bar)

Two Nespresso grand crus (proposed extraction volume – mean granulometry) Lungo (110mL – 365 µm)

Espresso (40mL – 275 µm)

Extraction and quantitative aroma measurement in-cup 10-20-40-80-110-150mL

Using Aqua Panna water

Each analysis point is an average of 3 extractions

P4

20 bar

Pre

ssu

re

Time

Quantitative measurement of 22 key coffee odorants in-cup

22 aroma compounds

• Isotope dilution assay

• SPME-GC-MS and SPME-GC-QQQ

P5

Quantitative measurement of 22 key coffee odorants in-cup: Varying volatility and polarity

Volatility Polarity Compound Aroma quality

High High 2,3-butanedione Buttery

Medium High 2,3-pentanedione Buttery

Low High 2-acetylpyrazine Popcorn

Low High Furfural Bready

Medium High Pyridine Fishy

Very high High Methanethiol Sulfury, cabbage, gassy

Low High 2-acetylpyridine Popcorn

Very high High Dimethylsulfide cabbage, sulfury

High Medium 2-methylbutanal malty, cocoa

High Medium 3-methylbutanal Malty

Low Medium Guaiacol Smoky, phenolic

Medium Medium N-methylpyrrole Roasty

Low Medium 2-ethyl-3,5-dimethylpyrazine Earthy

Low Medium 3-mercapto-3-methylbutylformate Roasted, sweaty

Medium Medium 2-furfurylthiol Roasty

Low Medium Phenylacetaldehyde Floral, honey

Medium Low Hexanal Green/grassy

Low Low 4-vinylguaiacol Spicy, medicinal

Medium Low Ethyl-2-methylbutanoate Fruity

Low Low 4-ethylguaiacol Smoky, medicinal

Low Low Skatol animal

Low Low Beta-damascenone Cooked apple

roasty

malty

fruity

buttery

earthy

floral,

honey

Cabbage,

sulfury

popcorn

grassy

smoky

animal

apple

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100 120 140 160

No

rmal

ized

in-c

up

aro

ma

qu

anti

ty

Extraction volume (mL)

High volatile High polar

Extraction kinetics differ among odorants

Extraction equation

Y =

P7

a x

b + x

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100 120 140 160

No

rmal

ize

d in

-cu

p a

rom

a q

uan

tity

Extraction volume (mL)

High volatile High polar

Low volatile Low polar

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100 120 140 160

No

rmal

ized

in-c

up

aro

ma

qu

anti

ty

Extraction volume (mL)

High volatile High polar

High volatile Medium polar

Low volatile Low polar

a / b

Volatility does not determine extraction behaviour

P8

0.00

0.05

0.10

0.15

0.20

0.25

0.30

-2.0 -1.0 0.0 1.0 2.0 3.0 4.0

Slo

pe

at o

rigi

n (

a/b

)

Volatility (Log [vapour pressure])

Lungo 20 bar

2-methylbutanal

2-acetylpyrazine

2,3-butanedione Low volatile High volatile

β-damascenone

Instead, polarity does impact the extraction behaviour

P9

High polar Low polar

y = -0.0464x + 0.1426R² = 0.6077

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

-1.5 -0.5 0.5 1.5 2.5 3.5

Slo

pe

at o

rigi

n (

a/b

)

Polarity (logP o/w)

Lungo 20 bar

2-methylbutanal

2,3-butanedione

2-acetylpyrazine

β-damascenone

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100 120 140 160

No

rmal

ize

d in

-cu

p a

rom

a q

uan

tity

Extraction volume (mL)

High volatile High polar

High volatile Medium polar

Low volatile Low polar

Aroma balance changes during extraction

P10

Lungo

! Based on normalized in-cup quantitative data,

Aroma values not taken into account !

13mL

High polar

Medium Polar

Low polar

144mL

High polar

Medium Polar

Low polar

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 80 100 120 140 160

No

rmal

ize

d in

-cu

p a

rom

a q

uan

tity

Extraction volume (mL)

365nm

275nm

Extraction of high polar compounds is affected by granulometry

P11

Finer granulometry faster extraction

High polar

Extraction kinetics of low polar

odorants is less affected

Granulometry

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 20 40 60 80 100 120 140 160N

orm

aliz

ed in

-cu

p a

rom

a q

uan

tity

Extraction volume (mL)

365nm

275nm

Low polar

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

-1.5 -0.5 0.5 1.5 2.5 3.5

Slo

pe

at o

rigi

n (

a/b

)

Polarity (log P o/w)

365nm

275nm

Finer granulometry faster extraction

P12

Sometimes deviating

extraction behaviour

Extraction profile of

odorants with lower polarity

less affected

Granulometry

High polar Low polar

Granulometry plays a key role for the extraction kinetics of high polar compounds

P13

• Extraction kinetics of coffee odorants

depend on the polarity

• R&G granulometry

• influences the extraction profile of

high polar odorants

• does not influence the extraction

behaviour of low polar odorants

Based on the above we can suggest that granulometry is one of the key

parameters for developing espresso coffees

Non-volatiles are also expected to play a key role and should be further

investigated