Leeds Thesis Template
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Determining the Detection Threshold for Perception of Selected Textural Attributes Tugba Aktar Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Food Science and Nutrition August 2015 The candidate confirms that the work submitted is her own, except where work which has formed part of jointly-authored publications has been included. The contribution of the candidate and the other authors to this work has been explicitly indicated below. The candidate confirms that appropriate credit has been given within the thesis where reference has been made to the work of others. Details of the jointly-authored publications are outlined on the next page. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement. © 2015 The University of Leeds and Tugba Aktar i Further details of the work from jointly-authored publications and the contributions of the candidate and the other authors to the work are included below: Chapter 3 Aktar, T., Chen, J., Ettelaie, R. and Holmes, M. (2015) 'Evaluation of the Sensory Correlation between Touch Sensitivity and the Capacity to Discriminate Viscosity', Journal of Sensory Studies, 30(2), 98-107 Details of authorship contributions: Aktar: conducted the experimental designs, data analysis, method validation, laboratory work and sensory evaluation tests, data interpretation, contributed to answer the reviewer’s comments and primary authorship. Chen, Ettelaie and Holmes: guidance, supervision, data interpretation, contributed to answer the reviewer's comments. Chapter 4 and Chapter 5 Aktar, T., Chen, J., Ettelaie, R. and Holmes, M. (2015) ‘Tactile sensitivity and the capability of soft-solid texture discrimination’, Journal of Texture Studies, in-press (DOI: 10.1111/jtxs.12142) Details of authorship contributions: Aktar: conducted the experimental designs, data analysis, method validation, laboratory work and sensory evaluation tests, data interpretation, contributed to answer the reviewer’s comments and primary authorship. Chen, Ettelaie and Holmes: guidance, supervision, data interpretation, contributed to answer the reviewer's comments. ii List of Publications and Awards Aktar, T., Chen, J., Ettelaie, R. and Holmes, M. (2015) 'Evaluation of the Sensory Correlation between Touch Sensitivity and the Capacity to Discriminate Viscosity', Journal of Sensory Studies, 30(2), 98-107. Aktar, T., Chen, J., Ettelaie, R. and Holmes, M. (2015) ‘Tactile sensitivity and the capability of soft-solid texture discrimination’, Journal of Texture Studies, in-press (DOI: 10.1111/jtxs.12142). Aktar, T., Chen, J., Ettelaie, R. and Holmes, M. (2014), Foods with Feeling, The 5th annual University of Leeds, Postgraduate Research rd Conference, 3 Research poster of the year. iii List of Accepted Conference Abstracts Aktar, T., Chen, J., Ettelaie, R., Holmes, M., ‘Little influence of tactile sensitivity on one’s capability of viscosity discrimination’ (2014), 3rd International Conference of Food Oral Processing - Physics, Physiology, and Psychology of Eating, Wageningen, Netherlands. Aktar, T., Chen, J., Ettelaie, R., Holmes, M., ‘Little influence of tactile sensitivity on one’s capability of viscosity discrimination’ (2014), University of Leeds Food Science and Nutrition, PhD Conference. Aktar, T., Chen, J., Ettelaie, R., Holmes, M., Foods with Feelings (2014), The 5th annual University of Leeds, Postgraduate Research Conference, Leeds, UK. Aktar, T., Chen, J., Ettelaie, R., Holmes, M., Foods with Feelings (2015), 2nd Food Industry Networking Conference, Leeds, UK. iv Acknowledgements I would like to give my acknowledgements and appreciation to many people who helped me on my rocky and long PhD journey. They all deserve a lot more than this page and should highlight it would not be possible without them. Firstly, my biggest thanks for my lovely family. My very much beloved mother Yuksel and father Yusuf, I am very glad to be your daughter and thank you for all the support, motivation, encouragement and belief you provided to me with all your heart. I love you more than anybody else in this world. Best sibling ever Tugce Aktar, I am not sure if you are aware but you are an awesome sister, I am very lucky to have you. You always encourage me to stand back whenever I am down. I love you very much. Another big contribution to my work came from my three supervisors: Professor Jianshe Chen who provided me with lots of personal and professional guidance, help, advice, support even though he was miles away for most of my time; Dr. Rammile Ettelaie with all the knowledge, brainstorms and support when I needed the most; and Dr. Melvin Holmes, who has supported me wholehearted regardless the situation despite all the technical support he has given. I was very lucky and it was privilege to work with all of you, and I want you to know that I will admire and respect you for my entire life. Additional thanks for helpful discussions and guidance to Dr. Brian Henson who provided me lots of knowledge and help from a new perspective, which made my work stronger. In addition, Dr. Laura Laguna Cruanes, Dr. Mahmood Akhtar and Ian Hardy deserves to be mentioned in this page with all the help, support and moral they have given to me. I am indebted to my sponsor, Turkish National Ministry of Education, for the financial support for my higher education. I am also grateful to my colleagues; especially to Woroud Alsanei who has been the most supportive, helpful, wholehearted friend to me and will be in my life forever. Also special thanks to Linda Pravinata, Fairuz Che Othman, Didem Sanver, Lilynorfeshah Mohd Shah and many more who gave me a chance to be in their life. v Abstract Texture perception and appreciation was found to be one of the determinative factors for preference, which lead to business success. Moreover, it was claimed to be vital for safe consumption in some cases for the vulnerable population (i.e. elderlies, babies or dysphagic patients). To create more desirable, preferable or safer foods it is necessary to understand the perception limits of the textural attributes and investigate if there are any correlations between other possible sensation systems. This study is motivated with the aim of finding thresholds for the selected attributes of texture (liquid viscosity, soft-solid firmness, soft-solid elasticity and solid surface roughness) and explore whether there is any correlation between texture sensation and tactile sensation systems, which was claimed to be responsible for texture sensation. Current study was examined with sensory tests on the fingertip and tongue for the textural attributes perception thresholds. Tactile sensation limits were observed with touch sensitivity tests and two-point discrimination tests. For each attribute, correlations with the tactile sensitivity were tested. Results revealed that the tactile sensation was not directly determinative in texture discrimination and correlation between texture discrimination and tactile sensation was not possible to be established for those attributes. Another approach was comparing the sensitivities between the fingertip and tongue. These two parts of the body seemed to have similar texture sensitivity, excluding the fluid viscosity. Due to this general similarity in discrimination of texture, we suggested that one could use fingertip texture discrimination threshold to predict the tongue threshold. Findings of this study have implications in the food industry and can contribute to the general understanding of the sensory scientists. For industry, obtained thresholds for particular attributes could be used as guidance for creating desirable food products. Moreover, if the same approach could be followed, thresholds for the vulnerable groups can be obtained and used for medical food production for creating safe to consume foods. On the other hand, methodologies and findings of this study could provide information to sensory scientists to map the full image of the texture sensation thresholds. vi Table of Contents List of Publications and Awards ............................................................ iii List of Accepted Conference Abstracts ................................................. iv Acknowledgements ................................................................................ v Abstract ................................................................................................. vi Table of Contents ................................................................................. vii List of Figures ...................................................................................... xii List of Tables ..................................................................................... xvii List of Equations .................................................................................. xx Abbreviations and Symbols ................................................................ xxi Chapter 1 Aims and Objectives .................................................................. 1 1.1 Aims of the Research............................................................. 1 Chapter 2 Introduction and Literature Review .......................................... 5 2.1 Introduction to Food Texture .................................................. 5 2.1.1 Classification ................................................................ 5 2.1.2 Definition .....................................................................