Effects of Bitterness, Roughness, PROP Taster Status, and Fungiform Papillae Density on Bread Acceptance a DISSERTATION SUBMITTE
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Effects of Bitterness, Roughness, PROP Taster Status, and Fungiform Papillae Density on Bread Acceptance A DISSERTATION SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Alyssa Joy Bakke IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Dr. Zata Vickers January 2010 © Alyssa Joy Bakke 2009 ACKNOWLEDGEMENTS My sincerest thanks to Zata Vickers for her mentorship, guidance, and unwavering support and encouragement throughout my academic journey. I will carry her influence throughout my life and career. Many thanks to the sensory panelists who participated in my studies. I wish to also thank Gary Reineccius, Sanford Weisberg, James Anderson, and Len Marquart for providing advice and serving on my examining committee. I would also like to acknowledge the Sensory Center, the Minnesota Agricultural Experiment Station, and the Joseph J. Warthesen 21 st Century Fellowship for funding this research. Thank you to my parents who inspired me to start this journey and provided gentle encouragement to see it through. Finally, I would like to thank my husband, John Chilton, whose help, encouragement, and sacrifice went above and beyond. From collating ballots to volunteering to be a guinea pig for papillae counting experimentation, he was always willing to lend a hand (or tongue) when I needed it. i ABSTRACT Consumption of whole grain foods, including whole wheat bread, has been linked to reduced risk of coronary heart disease, type II diabetes, certain cancers, and all cause mortality, but consumption falls far below recommended levels. Conventional wisdom dictates that refined bread is better liked than whole wheat bread, but support for this contention is scarce. If refined bread is preferred to whole wheat bread, determining the specific attributes or consumer characteristics that contribute to the disliking of whole wheat bread would provide food processors with the knowledge needed to develop technologies to improve the acceptability of whole wheat bread and to test acceptance of these products with consumers. In phase one of this study, we examined consumer preferences for refined and whole wheat breads. In phase two, we examined how two consumer characteristics, sensitivity to 6-n-propylthiouracil (PROP) and fungiform papillae density, affected perception of bitterness and roughness, two attributes that may contribute to whole wheat bread dislike. In phase three, we examined how three sensory properties, bitterness, roughness, and color and three consumer characteristics, bread type preference (whole or refined), perceived PROP intensity, and fungiform papillae density, affect bread liking. ii TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................. i ABSTRACT ........................................................................................................................ ii TABLE OF CONTENTS ................................................................................................... iii LIST OF TABLES .............................................................................................................. v LIST OF FIGURES ........................................................................................................... vi CHAPTER 1 ....................................................................................................................... 1 INTRODUCTION .............................................................................................................. 1 Literature Review............................................................................................................ 2 Whole grain benefits and consumption........................................................................... 2 Consumer bread preferences ........................................................................................... 2 Sensory features of whole wheat bread that may contribute to dislike........................... 4 Taste pathology that may contribute to whole wheat bread dislike ................................ 5 Objectives and hypotheses .............................................................................................. 9 CHAPTER 2 ..................................................................................................................... 11 CONSUMER ACCEPTANCE OF REFINED AND WHOLE WHEAT BREADS ........ 11 Introduction ................................................................................................................... 12 Materials and Methods .................................................................................................. 13 Results ........................................................................................................................... 19 Discussion ..................................................................................................................... 26 CHAPTER 3 ..................................................................................................................... 29 RELATIONSHIPS BETWEEN FUNGIFORM PAPILLAE DENSITY, PROP SENSITIVITY, AND BREAD ROUGHNESS PERCEPTION ....................................... 29 Introduction ................................................................................................................... 30 Materials and Methods .................................................................................................. 30 iii Results ........................................................................................................................... 33 Discussion ..................................................................................................................... 38 CHAPTER 4 ..................................................................................................................... 41 RELATIONSHIPS BETWEEN ROUGHNESS, BITTERNESS, PROP SENSITIVITY, FUNGIFORM PAPILLAE DENSITY, AND BREAD ACCEPTANCE......................... 41 Introduction ................................................................................................................... 43 Materials and methods .................................................................................................. 44 Results ........................................................................................................................... 52 Discussion ..................................................................................................................... 76 CHAPTER 5 ..................................................................................................................... 79 CONCLUSIONS............................................................................................................... 79 BIBLIOGRAPHY ............................................................................................................. 82 APPENDIX I .................................................................................................................... 92 Appendix I.I Sample Response Form for Study 1 ........................................................ 93 Appendix I.II SAS Code for Study 1 Data Analysis ................................................. 103 APPENDIX II ................................................................................................................. 110 Appendix II.I Sample Response Form for Study 2 .................................................... 111 Appendix II.II SAS Code for Study 2 Data Analysis ................................................ 116 APPENDIX III ................................................................................................................ 119 Appendix III.I Sample Response Form for Study 3 .................................................. 120 Appendix III.II SAS Code for Study 3 Data Analysis ................................................ 131 iv LIST OF TABLES Table 1. Study 1 Bread Formulations ............................................................................... 16 Table 2. Study 1 Mean Liking Ratings ............................................................................. 20 Table 3. Study 1 Liking Ratings by Bread Type Preference ............................................ 21 Table 4. Study 1 Liking Ratings by Bread Choice ........................................................... 22 Table 5. Study 1 Liking Ratings by Taster Status ............................................................ 23 Table 6. Study 1 Common Reasons for Bread Type Preference ...................................... 26 Table 7. Study 2 Mean Intensity Ratings .......................................................................... 34 Table 8. Study 3 Experimental Design ............................................................................. 43 Table 9. Study 3 Bran Sizing ............................................................................................ 45 Table 10. Study 3 Bread Formulations ............................................................................. 46 Table 11. Study 3 Significant Levels for Main Effects and Interactions .......................... 53 Table 12. Study 3 Mean Preference Ratings for Cereal Food Items ................................ 72 Table 13. Study 3 Mean Importance Ratings for Factors Affecting Food Choice ........... 74 Table 14. Study 3 Frequencies for Consumer Classification Groups ............................... 75 v LIST OF FIGURES Figure 1. Study 2 Roughnes Intensity