Impact of consumers’ bitter taste phenotype, familiarity, liking, demography and food lifestyle on the intake of bitter-tasting coarse vegetables Tove Kjær Beck PhD project thesis 2014 Food, metabolomics and Sensory Science Department of Food Science Aarhus University Kirstinebjergvej 10 DK-5792 Aarslev Denmark Main supervisor Associate professor Ulla Kidmose Food, metabolomics and Sensory Science Department of Food Science Aarhus University Co-supervisor Post doc Sidsel Jensen Food, metabolomics and Sensory Science Department of Food Science Aarhus University Opponents: Associate professor Marianne Hammershøj Food Chemistry and Technology Department of Food Science Aarhus University, Denmark Dr. Lisa Methven Food and Nutritional Sciences University of Reading, UK Professor Wender L. P. Bredie Section for Sensory and Consumer Sciences Department of Food Science University of Copenhagen, Denmark II I. Preface and acknowledgements This thesis is submitted in partly fulfilment of the requirements for the degree of Doctor of Science at Aarhus University (AU), Department of Food Science, in the research group Food, metabolomics and Sensory Science. All this work could not have been done without the financial support of The Danish Council for Strategic Research’s Programme Commission on Health, Food and Welfare (contract number: 2101-09-0109). and Graduate School of Science and Technology, Aarhus University. It is the result of inspiring work on part of the so-called MAXVEG project. “MAXVEG” stands for ‘Maximizing the taste and health value of plant food products - impact on vegetable consumption, consumer preferences and human health factors’. I am really grateful that this part of the project was appointed to me. It was a windfall and a privilege to join such a team on such fascinating work. I have been greatly helped by the teamwork of my colleagues, not least in the discussions generated by the huge amount of data collected in this study. Commuting between four different countries during this time, I am grateful to have had such support at my work base in Aarslev, Denmark. First of all thank you, Ulla and Sidsel with whom I have spent a lot of time discussing plans, results and not least manuscripts. Ulla Kidmose my main supervisor for this project, your passion for MAXVEG, your scientific supervision as well as your good spirit and kindness, and Sidsel Jensen for supervision and help, scientifically and as my good friend and faithful office companion in this period. I do not know how to thank you two enough. Secondly my thanks to the team in France, “merci beaucoup” to Sylvie Issanchou and Sophie Nicklaus at Institut National de la Recherche Agronomique (INRA), Dijon, who welcomed me five months in the spring and summer of 2012. A research stay which gave me new challenges, especially in regards to the French language and applications to the ethical committee, as well as giving my work and data set new dimensions. I could not have asked for a better research stay. A special mention and my gratitude to Aurélie Legrand with whom I worked closely together with at INRA. Besides my team of advisors I would like to thank others in the MAXVEG team; Per Bendix Jeppesen, Anne C. S. Thorup, Hanne Lakkenborg Kristensen, Marie Grønbæk, Birgitte Foged Nina Eggers, Chris Kjeldsen, Carsten Kronborg Bak and Sonni H. Simmelsgaard. Furthermore, the team in Aarslev producing the tested curly kale, white cabbage, celeriac and carrots Tina L. Magaard, and i Camilla Fjord and Margit Schacht for secretary assistance. I thank the illustrator Kirsten Tind and the publisher ‘Forlaget Koustrup & Co’, Denmark for the beautiful illustrations of coarse vegetables, I was allowed to use for the cover page, and also the non-professional illustrator Lynne Beck (my dear mother-in- law) for ‘drawing my thoughts’ so precisely in regards to the product-person- place illustration. My profound gratitude likewise goes to the various consumer groups in both countries, all the 1800 voluntary individuals who have been involved as test persons in Denmark and France or on the sensory panel in Aarslev. Furthermore, I would like to acknowledge my dear colleague and friend Line Mielby for thorough and competent proof-reading. Thanks to all my colleagues at Department of Food Science, Aarslev. It has been a privilege to have colleagues like you in the most positive and inspiring working environment I have ever had. Finally, I am deeply grateful for the support from all my friends, my parents Jonna and Laurids Christensen and the rest of the family and family-in law. To my husband Robert and our children Frederik, Anna and Elise - this is for you. I am grateful for your patience with me and my research that has brought us closer as a family and broadened our horizons as a cross-cultural study in more than one sense. This work has furthermore inspired me to use my senses, improved my understanding for the "supertaster status" of my father and increased my cabbage intake - as well as increased the intake of cabbage and root vegetables for everyone in my surroundings; my family, friends, my husband and not least my children. Tove Kjær Beck, Aarslev, August 2014 ii II. Abstract Coarse vegetables are grown throughout the world and are a very diverse sub- group of primary produce that consists primarily of cabbages and root vegetables. Consumption of these vegetables is found to reduce the risk of different lifestyle diseases such as certain forms of cancer, coronary heart diseases and type 2 diabetes. Some of the health benefits are ascribed to their phytochemical contents e.g. glucosinolates (GLSs) or phenolic compounds. Besides their health benefits, many of these phytochemicals also play a role for the sensory characteristics and specifically for the bitter taste of these coarse vegetables. Bitter taste in vegetables, and especially coarse vegetables, might be the main reason for dislike and rejection, due to innate response of rejection in the consumer. The perception of bitter taste is very complex and is for the individual affected by both genetics and environment. As evidenced in this PhD project the perception of the bitterness in the coarse vegetables is furthermore influenced by taste-taste interactions occurring between the bitter-tasting compounds and sugars in the vegetables. Intake of vegetables also of coarse vegetables, is below the established guidelines in Denmark as well as in other European countries, so it is necessary to gain more knowledge about coarse vegetables and some of the multiple factors influencing intake. The objectives of this PhD project in Sensory and Consumer Science were: 1) to study the relationship between taste and the content of health beneficial phytochemicals from selected coarse vegetables; 2) to test the potential of using a masking strategy to decrease the perceived bitterness from the phytochemicals and 3) to study the impact of bitter taste phenotype, familiarity, liking, socio-demography and food lifestyle of consumers on the intake of coarse vegetables. Sensory profiling and analyses of soluble sugars, GLSs and phenolic compounds were performed on eight curly kale and five white cabbage cultivars. Bitter taste was found to be an important sensory attribute, but was only loosely associated with the content of tested phytochemicals (Paper VI) or only associated with specific GLSs (Paper I). Sucrose as a masking agent for the bitter taste of Brassica was studied through sensory profiling of sucrose, two phytochemicals (sinigrin and goitrin) and of binary mixtures of these compounds. Each bitter compound was mixed with sucrose in aqueous solutions or in cabbage juice in a full factorial design. The result in Paper I showed that the intensity of perceived bitterness was significantly reduced (p<0.01) in both aqueous and cabbage juice solutions with increased sucrose content (Paper I). From testing the bitter taste phenotype in two comparable study populations in France and Denmark (the cross-cultural study) it was found that the quinine iii threshold value was lower in the Danish study population than in the French study population. Furthermore, it was found that women, in general, had a lower threshold value than men. An investigation of the influence of individual phenotype on the intake frequency of coarse vegetables showed that the phenotypic variation in taste explained differences in coarse vegetable intake for men in France (p<0.003), since a high threshold resulted in a higher intake of coarse vegetables. To examine the impact of other factors on consumers’ intake of 17 coarse vegetables, a study of the two populations in the cross-cultural study and an additional study population consisting of 1079 Danish consumers was performed with the aid of a comprehensive questionnaire (Papers II-V). In Denmark, four consumer clusters were identified based on the reported coarse vegetable intake (Paper II). The consumers in the clusters were profiled as being either: uninvol- ved, driven by health aspects, driven by traditions, or as individuals with a strong food engagement. Paper IV explored the distinct regional differences in the Danish population with regard to coarse vegetable intake frequencies across four different regions and the rural-urban gradient. People living in non-urban areas and outside Greater Copenhagen in Denmark were found to have a higher intake frequency of, e.g. curly kale. Furthermore, distinct intake patterns were seen for specific coarse vegetables in France and Denmark, and that women in Denmark had higher intake of most bitter coarse vegetables than men, while the opposite was seen in France (Paper III). Results from the abovementioned consumer studies demonstrate that consumer’ intake of coarse vegetables is not only affected by culture, taste phenotype and gender but also affected positively by other factors, namely higher familiarity and liking of coarse vegetables, older age, together with other socio-demographics, and various health and food lifestyle factors. This PhD project contributes new knowledge on the taste of coarse vegetables and has demonstrated that sensory quality cannot be ascribed to single bitter compounds tested here, but is a result of more complex interactions, e.g.