Characterization of surface appearance and color in fruits and vegetables using image analysis

123 Pages·2006·1.8 MB·English

PONTIFICIA UNIVERSIDAD CATOLICA DE CHILE
ESCUELA DE INGENIERIA
CHARACTERIZATION OF SURFACE
APPEARANCE AND COLOR IN SOME FRUITS
AND VEGETABLES BY IMAGE ANALYSIS

FERNANDO A. MENDOZA VILCARROMERO

Thesis submitted to the Office of Research and Graduate Studies in partial
fulfillment of the requirements for the Degree of Doctor in Engineering
Sciences
Advisor:
JOSÉ MIGUEL AGUILERA R.
Santiago de Chile, August, 2005
PONTIFICIA UNIVERSIDAD CATOLICA DE CHILE

ESCUELA DE INGENIERIA
Departamento de Ingeniería Química y Bioprocesos
CHARACTERIZATION OF SURFACE
APPEARANCE AND COLOR IN SOME FRUITS
AND VEGETABLES BY IMAGE ANALYSIS

FERNANDO A. MENDOZA VILCARROMERO
Members of the Committee:

JOSÉ MIGUEL AGUILERA R.
PEDRO BOUCHÓN A.
PETR DEJMEK
DOMINGO MERY Q.
FRANCO PEDRESCHI P.
JOSÉ FRANCISCO MUÑOZ P.

Thesis submitted to the Office of Research and Graduate Studies in partial
fulfillment of the requirements for the Degree of Doctor in Engineering
Sciences

Santiago de Chile, August, 2005
ii
To my adorable parents and sister,
Fernando, Faustita and Carolina.
To my loving wife and little son,
Sandrita and Vicente-Fernando.
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ACKNOWLEDGEMENTS

I would like to express my sincere gratitude to:
My supervisor, Professor José Miguel Aguilera, for his unconditional help, knowledge, his
advises and support throughout this work, even during my stay in Europe. My thanks are
also extended to all the formers and colleagues at the Department of Chemical Engineering
and Bioprocess in my University, for giving me the opportunity to work and share with
them.
Professor Petr Dejmek for his kind help, knowledge, and guidance and close collaboration
in my investigation during my stay at Lund University. My thanks are also extended to all
other former, technicians and colleagues in the Food Engineering Division at Lund
University in Sweden. Thanks for giving me the chance to know other culture.
MECESUP/PUC 9903 Project (Chile) for granting a doctoral scholarship at the Pontificia
Universidad Católica de Chile, and ALFA Network –ii: Food and Bioprocess Engineering
for Sustainability and Quality (EU Alfa Project II-0121-FA) for financial assistance to
develop part of this investigation at Lund University.
Special thanks to Dr. Margarita Naish, the leader of the ALFA programme in Europe, for
her continuous support and help during the most difficult moments in my stay in Sweden.
PhD Pedro Bouchon, the leader of the ALFA programme in Latino America, for his
advices and the trust that he deposited on me.
Mr. Thanos Papagiourgios, responsible for Quality Assurance in Inter Weichert & CO. KG
in Hamburg, for giving me the opportunity to directly know the quality control process of
bananas and other tropical fruits commercialized in Europe. His broad knowledge in fruits
quality control permitted me to improve my investigation in bananas.
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All my gratitude to Mrs. Fernanda Kattan and Mrs. Debby Meza for their kind help and
unconditional support in the administrative process. Thanks for facilitating the process for
getting information and documents requested by my wife.
Special thanks to my officemate in Lund University, Marcus Henningsson, for all those
discussions about life and science, and for sharing with me some aspects and experiences
of his own familiar life for successfully educating my little son.
My wife and little son, Sandrita and Vicente-Fernando, thank you both for existing,
without your love and motivation this work would never have been completed on time.
My parents, sister, brother-in-law and my two nephews: Fernando, Fausta, Carolina, Aldo,
Aldito and Nathalia, for their constant support, encouragement, unconditional love and
company, even over this long distance. Faustita, Carito, I now can feel you closer to me!
My closest friends in Europe: Pietro, Federico, Elena, Nathalie, Pablo, Stina, Olga, and
Jafar for your company and unconditional support during my time in Sweden.
Last, but not least, I want to thank my very closest friends in Chile Victor, Dante, Kike,
Roberto, Franco, Edgar, Roberto Q., Eduardo, Julio, Tato, Elva, Jorge, Nancy, Gloria,
María Paz and Misael for all the times together, for being supportive and true friends.
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LIST OF CONTENTS
Page
ACKNOWLEDGEMENTS...................................................................................................iv
LIST OF PUBLICATIONS...................................................................................................ix
LIST OF TABLES ..................................................................................................................x
LIST OF FIGURES................................................................................................................xi
ABSTRACT........................................................................................................................xiii
RESUMEN.........................................................................................................................xvii
I. INTRODUCTION AND OBJECTIVES......................................................................1
II. CALIBRATED COLOR MEASUREMENTS OF FOODS USING IMAGE
ANALYSIS...................................................................................................................6
II.1 Introduction..........................................................................................................6
II.2 Materials and methods .......................................................................................10
II.2.1 Fruits samples..........................................................................................10
II.2.2 Conventional colorimeter.........................................................................10
II.2.3 Computer vision system (CVS)...............................................................11
II.2.4 Calibration of the CVS.............................................................................12
II.2.5 Image segmentation.................................................................................14
II.2.6 Color spaces.............................................................................................14
II.2.7 Sensitivity analysis of CVS on color measurements...............................16
II.2.8 Statistical analysis....................................................................................19
II.4 Results and discussion........................................................................................19
II.3.1 Calibration of the CVS: Transformation of computer R’G’B’ into CIE
XYZ space.................................................................................................19
II.3.2 Sensitivity of CVS for color measurements.............................................22
II.3.3 Effect of curved surfaces on color measurements...................................27
II.4 Conclusions........................................................................................................33
II.5 References..........................................................................................................34
III. CLASSIFICATION OF BANANAS DURING RIPENING USING IMAGE
ANALYSIS.................................................................................................................37
III.1 Introduction........................................................................................................37
III.2 Materials and methods.......................................................................................39
III.2.1 Samples of bananas..................................................................................39
III.2.2 Computer vision system (CVS)...............................................................40
III.2.3 Image segmentation.................................................................................41
III.2.4 Color analysis...........................................................................................42
III.2.5 Brown spot analysis.................................................................................42
III.2.6 Image texture analysis..............................................................................43
III.2.7 Chemical analysis....................................................................................43
III.2.8 Classification............................................................................................44
III.2.9 Statistical analysis....................................................................................44
III.3 Results and discussion........................................................................................45
III.3.1 CVS versus HunterLab colorimeter.........................................................45
III.3.2 Color changes using CVS ........................................................................47
III.3.3 Development of brown spots...................................................................48
III.3.4 Bananas by ripening stages......................................................................52
III.3.5 Classification............................................................................................53
III.4 Conclusions ........................................................................................................55
III.5 References..........................................................................................................56
IV. PREDICTING RIPENING STAGES OF BANANAS USING COLOR
PARAMETERS..........................................................................................................61
IV.1 Introduction........................................................................................................61
IV.2 Materials and methods .......................................................................................62
IV.2.1Samples of bananas..................................................................................62
IV.2.2Computer vision system (CVS)...............................................................62
IV.2.3Color calibration......................................................................................63
IV.2.4Image segmentation.................................................................................63
IV.2.5Color analysis...........................................................................................64
IV.2.6Feature selection and classification..........................................................65
IV.3 Results and discussion........................................................................................65
IV.3.1Classification performance ......................................................................65
IV.3.2Discriminant power of selected features..................................................67
IV.3.3Practical application of CVS in the trade.................................................69
IV.4 Conclusions ........................................................................................................70
IV.5 References..........................................................................................................71
V. COLOR AND IMAGE TEXTURE IN CLASSIFICATION OF COMMERCIAL
POTATO CHIPS ........................................................................................................72
V.1 Introduction........................................................................................................72
V.2 Materials and methods .......................................................................................75
V.2.1 Samples of potato chips...........................................................................75
V.2.3 Image acquisition.....................................................................................75
V.2.3 Image segmentation.................................................................................76
V.2.4 Color analysis...........................................................................................77
V.2.5 Image texture analysis..............................................................................77
V.2.6 Quality testing and classification.............................................................78
V.2.7 Preference testing.....................................................................................79
V.3 Results and discussion........................................................................................81
V.3.1 Quality characterization of commercial potato chips..............................81
V.3.2 Preferences of the consumers versus extracted features..........................87
V.4 Conclusions ........................................................................................................89
V.5 References..........................................................................................................90
VI. GENERAL CONCLUSIONS.....................................................................................94
VII. FUTURE PROSPECTS..............................................................................................96
APPENDIX..........................................................................................................................96
Appendix A : Image segmentation.......................................................................................98
Appendix B : Classification using Discriminant analysis..................................................101
LIST OF PUBLICATIONS

This thesis is based on the following papers:
I. Calibrated color measurements of foods using image analysis. F. Mendoza, P.
Dejmek, and J.M. Aguilera. Submitted to Postharvest Biology and Technology, July,
2005.
II. Application of image analysis for classification of ripening bananas. F. Mendoza and
J.M. Aguilera. J. of Food Science, 69 (2004), 471-477.
III. Predicting ripening stages of bananas (Musa cavendish) by computer vision. F.
Mendoza, P. Dejmek, and J.M. Aguilera. Proc. 5th Int. Postharvest Symposium,
Verona, Italy. June 30th, 2004. ISHS Acta Horticulturae, 682 (2005), 1363-1367.
IV. Color and image texture in classification of commercial potato chips. F. Mendoza, P.
Dejmek, and J.M. Aguilera. Submitted to J. of Food Engineering, May, 2005.

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LIST OF TABLES
Page
Table II-1: Low and high levels of variables........................................................................17
Table II-2: Experimental matrix and results of L*, a*, and b* color scales for bananas.....25
Table III-1: Linear correlation coefficients between the average values of the nine
features extracted of the peel (average of seven bananas per stage) versus their
corresponding chemical parameters of the pulp and visually assessed stage of
ripening........................................................................................................................52
Table III-2: Performance of classification using three different methods to select
features........................................................................................................................54
Table IV-1: Selected color features and classification performance for each set ................66
Table V-1: Classification results of the four chip quality categories for training and
testing data ..................................................................................................................85

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