1. THE EFFECT OF MICROWAVE EXTRACTION ON THE
CHEMICAL COMPOSITION AND THE ANTIOXIDANT
PROPERTIES OF THE COFFEE RESIDUE
Iga Anna Turek
Prof. Manuel António Coimbra Rodrigues da Silva
Dr Cláudia Pereira Passos
Departamento de Química

2. Agenda
1. Aim of the work
2. General coffee composition
3. Microwave extraction
4. The content of the sugars
5. The content of the proteins
6. The content of the fat
7. The antioxidant capacity (AOC)
8. The volatile compounds
9. Summary
10. Conclusions

3. Aim of the work
1. Aim of the
work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 Define coffee residue composition
and the effect of microwave
extraction
 The content of sugars
 The content of proteins
 The content of fat
 The antioxidant properties
 in the oils
 in the residues and supernatants
 The volatile compounds in the oil from
coffee residue

4. General coffee composition
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions

5. Microwave extraction
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions

6. The sugars content
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
11. Questions
 Sugars = 79%
 48% Man; 26% Gal; 19.5% Glc; 6.5% Ara
 Microwave extraction
 1C MW: arabinogalactans & galactomannans
 Sn: Ara (12.4 %); Gal (48.8 %) & Man (31.9 %)
 R: the decrease of Ara and Gal
 2C MW: arabinogalactans & galactomannans
 Sn: Ara (5.4 %); Gal (38.8 %) & Man (41.4 %)
 R: the increase of Glc 19.5 % (bf MW) → 32.5%
(2C MW)

7. The proteins content
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 Proteins = 5 %
 27% Glu; 19% Leu; 11% Asp; 11% Ala; 8% Gly;
7% Val; 6% Pro; 5% Ile; 3% Phe; 2% Thr; 1%
Ser
 1C MW:
 R (6.5 %) & Sn (1.3 %)
 Similar composition – higher % of Asp, Glu &
Phe (comparing R bf MW and 1C MW)

8. The fat content
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 Oil = 13 %
 after MW
 R = 12-14 %
 Sn = 1 %

9. AOC of the oil
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
AOC of oil samples
0
5
10
15
20
25
30
35
coffee bf MW coffee 1C MW coffee 2C MW grape seed olive 1 olive 2 cereal seed
AOCintocopherolequivalent[10^(-3)M]

10. AOC of the residues and
supernatants
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
Antioxidant capacity
0
5
10
15
20
25
30
R Sn R af Sox aqueous
EC50
before MW - fat before MW - defatted 1C MW 2C MW

11. The volatile compounds
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 170 compounds – oil obtained from
coffee residue
0
1
2
3
4
5
6
7
8
100 200 300 400 500 600 700 800 900 1000
Acids Alcohols Aldehydes Esters Ethers Furanes Furfurals Pyrazines
Pyridines Pyrroles Thiopene Hydrocarbons Ketones Lactones

12. The volatile compounds
1. Aim of the
work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 Typical coffee-like aroma:
 furanes (2-furanmethanethiol)
 pyrazines:
 3,5-diethyl-2-methyl-pyrazine
 trimethyl-pyrazine
 2-ethyl-5-methyl-pyrazine
 Roasted odor:
 phenol (4-ethyl-2methoxy-phenol)
 pyrazines (2-ethyl-3,5-dimethyl-pyrazine; 2-(n-propyl)-pyrazine;
trimethyl-pyrazine; 2-methyl-pyrazine; 2,6-dimethyl-pyrazine; ethyl-
pyrazine; 2,3-dimethyl-pyrazine)
 thiopen (1-(2-thienyl)-ethanone)

13. The volatile compounds
1. Aim of the
work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 New compounds:
 alcohols (1-methyl-cyclopentanol; phenyl acetaldehyde; 2-
furanmethanol)
 furans (2-furanmethanol propanoate and acetate)
 pyrazine (2-acetyl-3-methylpyrazine)
 aldehyde (1-ethyl-1H-pyrrole-2-carboxaldehyde)
 hydrocarbones (2-pinene; (1S)-2,6,6-trimethylbicyclo(3,1,1)hept-
2-ene; p-xylene)
 ketone (1-phenyl-ethanone)
 lactone (5-methyl-2(3H)-furanon)

14. The summary
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 The main coffee residue compounds:
polysaccharides (80 %), lipids (13 %) and proteins
(5 %)
 Microwave extraction:
 Polysaccharides
 1C MW – 13 % arabinogalactans & 38 %
galactomannans
 2C MW – 4 % arabinogalactans & 53 %
galactomannans
 Proteins – Sn (1.3 %); no significant change in the
composition
 Oil – Sn (1.3 %)
 AOC of oil, R & Sn - high
 MW is lowering AOC
 R has lower AOC than correspondent Sn
 Oil obtained from coffee residue has enjoyable and
characteristic for coffee smell
 mainly furanes and pyrazines are responsible
other
2%
proteins
5%
lipids
13%
sugars
80%

15. The conclusions
1. Aim of the work
2. Coffee
composition
3. Microwave
extraction
4. Sugars
5. Proteins
6. Fat
7. AOC
8. Volatile
compounds
9. Summary
10. Conclusions
 Those results can be the basis for
future analysis:
 of polysaccharide microwave extraction
in different microwave conditions to
obtain the highest extraction yield
 the high antioxidant capacity of coffee oil
has a high potential for future
applications in other food products.
 the pleasant aroma of coffee oil
(remains in the residue after the
microwave extraction) can be used in
food products, in cosmetics and
perfumes

16. Thank you 
Iga Anna Turek