Characterization of the Roasting Temperature and Time-Dependent

Chapter 23

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on December 24, 2015 | http://pubs.acs.org Publication Date: January 15, 2000 | doi: 10.1021/bk-2000-0754.ch023

Characterization of the Roasting Temperature and Time-Dependent Physicochemical and Sensory Evaluation of Various Coffee Beans Y . S. K o Department of Food and Nutrition, Hanyang University, Seoul 133-791, Korea

Roasting temperature and time-dependent changes in bean density (puffing), color, moisture and soluble solids content (percolation) o f Colombian, Brazil and Madagascar coffee beans were studied under normal and quick roasting conditions. The greater bean expansion effects were observed the shorter the roasting time, and the shorter roasting time resulted from higher heating and starting temperature. Roast color ranges are 37.0-40.0, 42.5-45.0 and 46.0-49.0 in Colombian, Brazil and Madagascar, respectively. From the P C A test analysis, better flavor and better mouth-feel were obtained with shorter roasting time in all three coffee beans. Overall quality of roast beans improved with higher temperature and shorter roast time in terms of aromatic impact, cup strength, intensity of taste, and quality of extract.

Roasting time and temperature of green coffee beans determines color, flavor and taste. Coffee beans may be roasted by normal or quick roasting processes. It takes 1315 minutes for normal roasting and 2-3 minutes for quick roasting. Quick roasting method has the advantage of short duration of roasting. Roasting methods can be classified into two procedures. One of these is Shop Roasting (use Shop roaster), which is a hot air impingement method, and the other one is the Probat Roasting, which is an indirect heating method.

Purpose This study is aimed to determine difference between normal and quick roasting when varying roasting temperature and to determine the physicochemical and sensory properties of normal and quick roasted coffees. In addition, this study compares qualities of coffee beans by Shop Roasting and Probat Roasting. Results of this study

216

© 2000 American Chemical Society

In Caffeinated Beverages; Parliment, Thomas H., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2000.

217 will provide information on the overall equipment and manufacturing process for roasting beans to produce optimum product.


Materials and Preparation Colombian, Brazil and Madagascar green coffee beans were used as samples in this study (1-3). For the sample preparation, Shop Roasting and Probat Roasting were used for each sample of green coffee bean. For example Shop Roasting of Colombian beans had 4 roasting times. That is, process A takes 1-2 minutes, process Β takes 2-3 minutes, process C takes 3-7 minutes and process D takes 8-14 minutes. The preparation of samples using Probat Roasting method was carried out manually according to the degree of roast desired and took 12-16 minutes. The heating parameters are shown in Table 1.

Table I. Treatment of Green Coffee Bean. Type of Roasting

Kind of coffee bean

Colombia

Shop Roasting

Brazil

Madagascar

Probat Roasting

Heating Temp.

Starting Temp.

CQ

fQ

Final Temp.

CQ

A

300

270

250-244

Β

285

245

246-240

C

260

225

232-226

D

245

220

216-215

A

300

270

250-244

Β

285

245

246-240

C

260

225

232-226

D

245

220

215

A

300

270

252-246

Β

285

245

250-244

C

260

225

236-230

D

245

220

216

Colombia

#1

Brazil

#2

Madagascar

#3

Analytical Measurements Analytical measurements consisted of roasting time, roasted bean density, roast color, roast moisture and soluble solids. Flavor components in each sample using


218 peak area of gas chromatogram measured by internal standard was determined (4-8). For the sensory evaluation, the strength and quality of each sample by well-trained panels was measured and preference for flavor and taste was examined (9-13).

Results


Table II shows roasting time for each green bean. With each of the green coffee beans; Colombian, Brazil, and Madagascar, the higher the heating temperature and start temperature, the shorter the roasting time.

Table II. Roasting Time for Each Green Coffee Bean Types

A

Β

r* \^

pk LI

Probat Roasting

Final Temp. CO 250

Colombia (min) 1.55

Brazil (min) 1.52

Madagascar (min) 1.58

248 246

1.53 1.48

1.50 1.47

1.51

244

1.44

1.43

1.45

246

2.56

2.48

2.54

244

2.34 2.26

2.38 2.22

2.36

242 240

2.21

2.15

2.20

232

6.52

6.39

6.04

230

4.44

5.40

5.00

228

4.11

4.30

4.21

226

3.49

3.46

4.59

216

12.30

14.30

14.00

1.54

2.26

216

11.10

12.30

12.00

215

9.40

10.30

10.30

215

8.12

8.30

#1

14.20

14.10

#2

13.48

13.24

15.05

#3

13.25

12.44

14.50

15.30



219 Figure 1 shows the results of roast bean density, namely expansion of each green coffee bean. The shorter the roasting time, the higher the expansion and the greater the expansion, the higher the soluble solids yield. Figures 2 and 3 show the results of the roast bean moisture and roast color of each green coffee bean, respectively. Figure 4 shows the results of soluble solid of each green coffee bean. For example, maximum value of Shop Roasting is 1.580 and maximum value of Probat Roasting is 1.179. Thus there is a significant difference between these roasting processes. Figure 5 shows the summary of the results of the physical analysis. This figure is summarized in terms of similar roast color for several conditions and compares the roasting bean density, roasting bean moisture and soluble solid of the samples. A , B , C and D are the samples used with Shop Roasting which is method of hot air impingement and Ε is Probat roasting which is indirect heating. Table HI shows the Principle Component Analysis (PCA) of Colombian beans. With Colombian, floral, sharp and sour odors were detected to be stronger, but tarry odor was detected to be one step lighter than Brazil and Madagascar beans.

Table III. The P C A Results of Colombia Beans Quick Roasting Probat Roasting

Degree of Roast Aromatic Impact

R-SL-C LOW-MOD

A

Β

C

D

R-SL-C

R-SL-C

R-SL-C

R-SL-C

2 steps

2 steps

1 step

same*

strong

strong

strong

Aromatic Character Floral

1

1-2

1-2

1-2

1

Sharp

X-l

1-2

1-2

1

X-l

1

X-l

X-l

X-l

X-l

LT-MED

2 steps strong

2 steps strong

1 step strong

same*

Sour

1-2

1-2

1-2

1-2

1-2

Bitter

1-2

1-2

1-2

1-2

1-2

I

1-2

1-2

1

1

Tarry Cup Strength Basic Taste Intensity

Astringent

* : same as Brazil and Madagascar beans. Table IV shows the P C A results of Brazil coffee. Earthy odor was detected to be one step stronger and tarry odor was detected to be one step lighter. Table V shows P C A results of Madagascar. With Madagascar, cereal odor was detected to be one step stronger and tarry odor was detected to be one step lighter. It was observed that



• m

.

. az

.

, m

1 Probat Roasting

Probat Roasting Figure 1. Roast bean density of each coffee bean sample.



221

244

246

240

248

242

223

246

RrriTenp.[°q

RrdTerrp.[°q

225

244

230

216

215

RrBlTerrpfq

0

RnalTenp.[ q Quick Roasting

Colombia -Φ— Probat Roasting m

m Probat Roasting

-A—

Brazil Madagascar

m

Figure 2. Roast bean moisture content of each coffee bean sample.



222

, #1

,

,

,

#2

#3

1

Probat Roasting

M a d a g a s c a r

Probat Roast Figure 3. Roast color of each coffee bean sample.



223

Probat Roasting

#2

—•—

Colombia

—Φ—

Brazil

—

A

Madagascar

#3

ProbetFtesting Figure 4. Soluble solid of each coffee bean sample.



ao.

RDastTirre

Roastlrm

—Colombia —Φ— —•—

Brazil Madagascar

Figure 5. Summary ofphysical analysis of each coffee bean sample.


225 with Colombian, Brazil and Madagascar, the shorter the roasting time, the stronger the overall flavor and aroma.

Table IV. The P C A Results of Brazil Beans Quick Roasting rrooai Koasnng R-SL-C


Degree of Roast

moderate

Aromatic Impact

Β 1 step strong 2 steps strong

C same*

D same*

1 step strong

same*

1-2

1-2

1-2

1

1

X-l 1

1

same*

same*

A 1 step strong 2 steps strong

Aromatic Character Earthy

1

Sharp Tarry

X-l

X-l

medium

1 step strong

1 step strong

1

Cup Strength Basic Taste Intensity Sour Bitter Astringent

1

1

1-2

1-2

1

1-2

1-2

1-2

1-2

1-2

1

1-2

1-2

1-2

1

same as Brazil and Madagascar beans.

Table V . The P C A Results of Madagascar Beans Probat Roasting Degree of Roast Aromatic Impact

A 1 step strong 2 steps strong

Β

C

D

1 step strong 2 steps strong

same*

1 step light same*

1-2

1-2

1-2

1-2

1-2

1-2

1

1

1-2

1-2

medium

2 steps strong

2 steps strong

R-SL-C moderate

1 steps strong

Aromatic Character Cereal Tarry Cup Strength

1 step strong

same*

Basic Taste Intensity Sour Bitter Astringent

1

1

1

1

1

1-2

1-2

1-2

1-2

1-2

1

1-2

1-2

1-2

1

* : same as Brazil and Madagascar beans.


226


Table VI. Analysis of Flavor Components of Colombian Beams by G C Shop Roasting A

Β

C

D

Probat Roasting

Light aroma

686

558

544

402

542

Medium aroma

145

127

139

130

182

Heavy aroma

600

439

409

221

266

1431

1124

1092

753

990 20 132

Aromatic Components

Total aroma Acetaldehyde

33

36

22

11

Acetoin Furan

138

116

125

92

17

10

16

14

14

Isobutyric acid

30

30

28

20

27

Diacetyl

48

35

32

14

23

2,3-Pentanededione

-

-

39

17

28

Methyl ethyl ketone

27

19

27

22

28

2-Methylfuran

66

51

53

60

79

25

37

37

39 37

37

Pyrazine

43

25

38 60

30 83

39 110

Furfural

108

69

62

18

29

Furfuryl alcohol

152

144

65

42

59

Methylpyrazine

28

28

25

17

16

-

29

27

18

18

20

22

16

16

pH

5.214

5.156

5.279

5.662

5.491

TA

1.227

1.171

1.025

0.559

0.74

Isovaleraldehyde 2-Methylbutanal

Dimethylpyrazine Trimethylpyrazine

42


227


Table V I L Analysis of Flavor Components of Brazil Beans by G C

A

Shop Roasting Β

C

D

Probat Roasting

Light aroma

564

638

498

170 479

200 451

285 110 212

409

Medium aroma Heavy aroma

187 231

228 384

Total aroma

1213

1289

607

827

1110

nrummiu uumpunems

Acetaldehyde

19

31

8

17

16

Acetoin

151

77

95

Furan

127 10

15

6

10

118 12

Isobutyric acid

30

39

17

Diacetyl

40

45

16

22 14

23

2,3-Pentanededione

39

49

18

20

28

Methyl ethyl ketone

22

28

15

23

25

2-Methylfuran

50

50

34

46

63

Isovaleraldehyde

37

47

19

28

29

2-Methylbutanai

37

48

23

37

36

Pyrazine

63

88

64

120

141

26

Furfural

59

62

20

15

25

Furfuryl alcohol

138

78

50

55

122

Methylpyrazine

35 34

39 36

17

22

24

17

22

25 22

Dimethy Ipyrazine Trimethylpyrazine

25

24

20

16

pH

5.343

5.377

5.589

5.811

5.702

TA

0.965

0.922

0.656

0.442

0.531


228

Table VIII. Analysis of Flavor Components of Madagascar Beans by G C A

Λ


Aromatic components Light aroma Medium aroma Heavy aroma Total aroma

Shop Roasting B C

D

Probat „ Roasting

608 174

551 187

2

A 599

738 197

609 191

125 302

423

337

304

328

1026

1358

1137

1086

1066

Acetaldehyde

39

35

26

24

24

Acetoin

138

163

145

132

135

15

20

19

18

19

Furan Isobutyric acid

56

61

33

48

29

Diacetyl

34

41

27

25

23

2,3-Pentanededione

25

31

19

20

14

Methyl ethyl ketone

26

32

36

30

33

2-Methylfuran

57

73

77

76

80

Isovaleraldehyde

57

68

40

52

33

2-Methylbutanal

61

74

48

65

44

Pyrazine

50

91

65

64

81

22

21

Furfural

37

44

27

Furfuryl alcohol

72

119

64

77

101

Methylpyrazine Dimethylpyrazine Trimethylpyrazine

28 27 19

36 37 26

32 36 26

29 31 21

23 26 24

pH

5.508

5.56

5.826

6,147

5.834

TA

0.62

0.504

0.317

0.092

0.325



229 Tables VI, VII and VIII show the flavor component results of each green coffee bean by G C analysis. With all samples, Shop Roasting which takes about 3 minutes of roasting gave better flavor extracts by percolation than Probat Roasting which takes 13-15 minutes and is the current manufacturing method. With Colombian beans, longer roasting time results in less total aroma. Probat Roasting is currently used commercially and shows more excellent results than D of Shop Roasting. With Brazil, Probat Roasting method shows a greater amount of total aroma and diketones, namely diacetyl and 2,3-pentanedione, and more 2-methylfuran than C and D. Probat Roasting method shows similar results to C and D. However, overall, Probat Roasting method is considered to produce inferior flavor quality to A and Β. With Madagascar coffee, Probat Roasting method yielded lower amount of total aroma than Β of Shop Roasting and similar level of total aroma under other roasting conditions. Additionally, it gave a lower diketone level and a higher level of 2methylfuran than those with the Shop Roasting method. Overall it gave inferior quality compared to Shop Roasting method.

Conclusions Overall, the higher the roasting temperature and the shorter the roasting time, the better the quality of roasted bean. Quick roasting method gave better expansion, therefore, greater yield of soluble solid extracts and higher cup strength than with Probat roasting. The shorter the roasting time, the higher the aromatic impact, cup strength, intensity of taste and the richer aroma. Quick roasting methods gave higher aromatic flavor and one step less tarry odor than the Probat roast. The shorter the roasting time, the better were extracts by percolation based on chromatographic results.

References 1. 2. 3. 4. 5. 6. 7. 8. 9.

Sivetz, M.; Desrosier, Ν. "Coffee Technology", A V I Publishing Company, Westport, CT, 1979, pp. 209-213 Shibamoto, T. ASIC, 14th, Colloque, San Francisco, 1991, pp. 277-285 Williams, Α.; Arnold, G. J. Sci. Food Agric. 1985, 36, 204. Wada, K . ; Ohgama, S.; Sasaki, H . ; Shimoda, M.; Osajima, Y. Agric. Biol. Chem. 1987, 51, 1745-1752 Blank, I.; Sen, Α.; Grosch W. Ζ. Lebensm. Unters. Forsch. 1992, 195, 239-245 Newmann, R.; Molnar, P. Sensorische Lebensmitteluntersuchung, 2 Auflage, 1991, Fachbuchverlag Leipzig. Koehler, W.; Schachtel, G . ; Voleskr, P. Biostatistik, Springer Verlag, Berlin, 1996. Shibamoto, T. ASIC 14, Colloque, 1991, pp. 107-116 Semmelroch, P.; Grosch, W. Lebensm. Wiss -u. Technol. 28, 1995 1-4.

10. Semmelroch, S. Diss. Deutsche Forschungsanstalt für Lebensmittelchemie, Garching, Germany, 1995. 11. Procida, G.; Palol, D. Riv. Ital Eppos, 1997, pp. 251-261 12. Brevard, H . ; Feria-Morales, Α.; Krebs, Y.; Menouk, A - F . Colloq. Sce. Int. Café, 1977, pp. 211-213 13. Schwencke, B.; Baltes, W. Lebensmittelchemie, 1998, 52, 33-56


Characterization of the Roasting Temperature and Time-Dependent

Recommend Documents