quality enhancement of coffee with acid and enzyme treatment

131 Pages·2007·4.95 MB·English

QUALITY ENHANCEMENT OF COFFEE WITH ACID AND ENZYME TREATMENT

By

LUIS FEDERICO MARTINEZ

A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2007
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©2007 Luis Federico Martinez

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To my Wife, Son, Mother and Grandparents

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ACKNOWLEDGMENTS
I would like to thank my advisor Dr. Murat O. Balaban for all his support and guidance
through the last three years of my life and throughout my research. I have learned from him how
important it is to show productivity in everything we do, to pursue goals without intimidation, to
work as a team and to use critical thinking in every aspect of our life. I would also like to thank
Dr. Marty R. Marshall and Dr. Allen Wysocki for all their support and for being part of my
committee, Dr. Charles Sims for helping me with sensory evaluation, Dr. Lynette Orellana and
the University of Puerto Rico Experimental Station in Adjuntas, Cinnamon Bay Coffee - Ambex
Roasters Inc. for their help with roasting and cupping, Joseph Tsai for helping with the SEM and
all professors and staff that have contributed to this dissertation.
I would like to thank my wife, my mother, grand parents and all my family for all their
help and support every day of my life.
I would also like to thank all my dear friends and coworkers for their help with the
trained panel and the experiments, but especially I would like to thank Lorenzo Puentes, Stefan
Crynen, Max Ochsenius, Jose Aparicio, Alberto Azeredo, Thelma Calix, Jorge Cardona and
Wendy Marin for all the long hours they spent helping me in all aspects of my research.

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TABLE OF CONTENTS

Page
ACKNOWLEDGMENTS...............................................................................................................4
LIST OF TABLES...........................................................................................................................7
LIST OF FIGURES.........................................................................................................................9
ABSTRACT...................................................................................................................................12
CHAPTER
1 INTRODUCTION..................................................................................................................14
2 LITERATURE REVIEW.......................................................................................................16
Coffee: Composition, Production and Overview....................................................................16
Coffee Processing...................................................................................................................20
Introduction.....................................................................................................................20
Plant Selection and Harvesting........................................................................................20
Coffee Processing Methods.............................................................................................20
Dry processing..........................................................................................................21
Wet processing.........................................................................................................22
Pulped natural process..............................................................................................23
Ecological process....................................................................................................23
Coffee Drying..................................................................................................................24
Coffee Roasting...............................................................................................................25
Introduction..............................................................................................................25
Roasting techniques..................................................................................................26
Changes produced by roasting.................................................................................28
Grinding...........................................................................................................................32
Coffee Aroma..................................................................................................................32
Cup Quality.....................................................................................................................34
Kopi Luwak............................................................................................................................35
Instrumental Analysis.............................................................................................................37
Machine Vision...............................................................................................................37
Electronic Nose...............................................................................................................38
Scanning Electron Microscope........................................................................................39
Sensory Analysis....................................................................................................................40
Objective of the Study............................................................................................................41
3 MATERIALS AND METHODS...........................................................................................42
Preliminary Experiments........................................................................................................42
Experiments............................................................................................................................50
Coffee Harvesting............................................................................................................50
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Green Coffee Processing.................................................................................................50
Green Coffee Storage......................................................................................................51
Coffee Treatments...........................................................................................................51
Coffee Roasting...............................................................................................................52
Coffee Grinding and Brewing.........................................................................................53
Experimental Design..............................................................................................................53
Color and Texture Analysis by Machine Vision and Lens Eye Software..............................55
Electronic Nose.......................................................................................................................56
Sensory Analysis....................................................................................................................58
Coffee Cupping.......................................................................................................................59
Scanning Electron Microscope...............................................................................................59
4 RESULTS AND DISCUSSION.............................................................................................61
Sensory analysis.......................................................................................................61
Scanning electron microscope..................................................................................66
Electronic nose.........................................................................................................76
Machine vision.........................................................................................................79
5 SUMMARY AND CONCLUSIONS.....................................................................................83
6 FUTURE WORK....................................................................................................................86
APPENDIX
A CUPPING AND SENSORY EVALUATION.......................................................................88
B SCANNING ELECTRON MICROSCOPE IMAGES AND ANALYSIS..........................101
C ELECTRONIC NOSE DATA AND GRAPHS...................................................................118
D MACHINE VISION IMAGES.............................................................................................121
E COFFEE PROCESSING......................................................................................................124
LIST OF REFERENCES.............................................................................................................125
BIOGRAPHICAL SKETCH.......................................................................................................131

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LIST OF TABLES
Table page

2-1 Coffee production in the 10 largest producing countries and world total..........................19
2-2 Coffee roast colors and characteristics..............................................................................27
2-3 Roasting characteristics of the arabica and robusta coffees..............................................30
2-4 Content of chlorogenic acids in green and roasted coffees and percentage loss during
roasting...............................................................................................................................31
2-5 Important aroma compounds present in roasted coffee.....................................................33
3-1 Sensory evaluation results (Batch A vs. B vs. C)..............................................................45
3-2 Temperature programming conditions used for GC-O......................................................47
3-3 Moisture content for green, untreated and treated coffee beans........................................53
3-4 Nikon D50 camera settings................................................................................................56
4-1 Triangle test sensory analysis results (treated coffee vs. controls)....................................61
4-2 Trained panel results (treated vs. control coffee samples).................................................62
4-3 Professional cupping evaluation of roasted coffee samples # 501 and # 105....................64
4-4 Visual texture analysis results: Color primitives with threshold = 35...............................70
4-5 SAS results for texture analysis color primitives with threshold = 35..............................72
4-6 Visual texture analysis results: Texture primitives with threshold = 25............................73
4-7 SAS results for texture analysis texture primitives with threshold = 25............................73
4-8 Visual texture analysis results: Texture primitives with threshold = 15............................74
4-9 SAS results for texture analysis texture primitives with threshold = 15............................74
4-10 Visual texture analysis results: Contour analysis L* contour > 40....................................75
4-11 SAS results for contour analysis L* contour > 40.............................................................75
4-12 Color analysis results: Green, roasted and ground (treated and control)...........................80
4-13 SAS results for color analysis on green coffee beans........................................................80
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4-14 SAS results for color analysis on whole roasted coffee beans...........................................81
4-15 SAS results for rolor rnalysis on ground roasted coffee beans..........................................82
A-1 Summa Coffee Academy TM cupping and sensory evaluation form..................................88
A-2 Treated coffee rheologydata (run 1)..................................................................................89
A-3 Treated coffee rheology Data (run 2).................................................................................90
A-4 Control coffee rheology data (run 1).................................................................................92
A-3 Control coffee rheology data (run 2).................................................................................93
A-4 Olfactometry port aroma active smell impressions...........................................................95
A-4 Trained panel sample ballot (training sessions).................................................................97
A-5 Trained panel sample ballot (final bitterness panel)..........................................................98
A-7 Trained panel individual results (bitterness scale 1-15)....................................................99
C-1 ΔR/R results of most sensitive 12 sensors for all samples...............................................118

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LIST OF FIGURES
Figure page

2-1 Coffee producing regions of the world..............................................................................16
2-2 Various stages from the bean in parch up to the emergence of the first foliage leaf
pair.....................................................................................................................................17
2-3 Fruit development..............................................................................................................17
2-4 Cross section of the coffee cherry (left) and stereo microscope view of the coffee
cherry (right)......................................................................................................................18
2-5 Patio drying of coffee: Almost dry stage...........................................................................21
2-6 Fermenting tank.................................................................................................................23
2-7 Ecological coffee processing machine. A) The machine as a whole. B) The pulper.
C) Friction drums for mucilage removal...........................................................................24
2-8 Coffee roasting picture.......................................................................................................26
2-9 Coffee cupping...................................................................................................................35
2-10 Kopi Luwak coffee............................................................................................................36
2-11 Scanning electron microscope image of Kopi Luwak.......................................................40
3-1 Roasting profile temperature vs. time (Batch A)...............................................................44
3-2 Roasting profile temperature vs. time (Batch B)...............................................................44
3-3 Roasting profile temperature vs. time (Batch C)...............................................................45
3-4 Top) GC, FID. Chromatogram. Bottom) GC-O Chromatogram: Treated Coffee
Beans..................................................................................................................................48
3-5 Top) GC, FID. Chromatogram. Bottom) GC-O Chromatogram: Control Coffee
Beans..................................................................................................................................49
3-6 Coffee storage jars.............................................................................................................51
3-7 Coffee drying.....................................................................................................................52
3-8 Ambex YM-15 coffee roaster............................................................................................52
3-9 Coffee roasting profile temperature vs. time (treated beans).............................................54
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3-10 Coffee roasting profile temperature vs. time (control beans)............................................55
3-11 Sample holder designed for electronic nose analysis........................................................57
3-12 Field emission scanning electron microscope JEOL JSM 6330F......................................60
4-2 Scanning electron microscope picture of a control (raw) bean at 100x magnification.....67
4-3 Scanning electron microscope picture of a treated (raw) bean at 100x magnification......67
4-4 Scanning electron microscope pictures of a treated bean at 500x (left) and 3000x
(right) magnification..........................................................................................................68
4-6 Treated samples and controls color primitives analysis (texture threshold = 35)..............70
4-7 Treated samples and controls texture primitives analysis (threshold = 15).......................71
4-8 Treated samples and controls contour analysis (L* contour > 40)....................................71
4-9 Example of ∆R/R values for each sensor (Batch A)..........................................................77
4-10 ∆R/R values for each sensor (control coffee sample Run 1).............................................77
4-11 ∆R/R values for each sensor (treated coffee sample Run 1)..............................................78
4-12 Squared Mahalanobis distances for all samples.................................................................78
4-13 Scatterplot of root 1 vs. root 2 of unstandardized canonical scores for batch A, B, C,
treated and control samples................................................................................................79
A-1 Series of pictures of the coffee taste panel.........................................................................96
B.1 Controls color primitives images and results (color threshold = 35)...............................101
B.2 Controls color primitives images and results (color threshold = 35)...............................102
B.3 Controls color primitives images and results (color threshold = 35)...............................103
B.4 Controls contour images and results (L* contour > 40)..................................................104
B.5 Controls contour images and results (L* contour > 40)..................................................105
B.6 Controls texture primitives images and results (texture threshold = 15).........................106
B.7 Controls texture primitives images and results (texture threshold = 15).........................107
B.8 Controls texture primitives images and results (texture threshold = 25).........................108
B.9 Controls texture primitives images and results (texture threshold = 25).........................109
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