New methodological approaches to investigate vegetables preference among consumers

Improved population nutrition is one of the key factors underlying increased health and longevity (Chernoff, 2001) and vegetables are often identified as the most important part of a diet recognized as beneficial for health (Appleton et al., 2016). The adoption of diets rich in vegetables resulted in positive effects not only for human health but also for planetary health. (Whitmee et al., 2015). Dietary change through an increase of plant-based foods to the detriment of animal-based foods has been suggested to be necessary to reduce the environmental impact of the food system (Notarnicola et al., 2017). Despite the recommendation, studies show that a large proportion of consumers consume fewer vegetables than recommended. Therefore, for improved health and diet sustainability, an increased intake of vegetables is required. These interventions should be based on in-depth understanding of the underlying determinants of the preference for vegetables and methodologies aimed to assess consumer preferences and perception in an effective and reliable way. An aspect that links many of the new methodological approaches in sensory and consumer science is the process of categorization. Categorization is a natural cognitive process where objects with common characteristics are grouped and inference is made about their properties, in order to obtain considerable information with minimum cognitive effort (Rosch & Lloyd, 1978). Among the methods based on categorization is the Free sorting task (Lawless et al., 1995), a procedure that can be used with consumers to study similarities among food products. There are a number of methodologies of implicit measure related to categorization, such as the Implicit association test (Greenwald et al., 1998), that find in the process of categorization the operative task carried out by subjects during the implicit test. Considering the relevance of categorization among the approaches to overcome the current limits in sensory and consumer research is therefore of interest in studying issues strongly related to the preference for vegetables with the contribution of the process of categorization. Many issues related to the study of preference for vegetables need attention. For instance, beside the suggestion to consume a specific number of portions of vegetable, of particular importance is the comprehension of which items consumers include in the category “vegetable”, highlighting possible mismatches between guidelines and consumers. Considering these aspects, a deeper comprehension of how consumers represent the vegetable category may be useful to improve the effectiveness of dietary guidelines and increase the consumption of recognized vegetables. This research question was explored in Study I recurring to the prototype theory of categorization, in order to investigate the relationships between the typicality of the dishes and of the dish features with expected liking among consumers. Taking into consideration the increasing interest of interventions targeted at older adults and children to increase vegetable consumption (Appleton et al., 2016), the use of investigative tools that allow evaluation of the perceptions and preferences in an effective and reliable way is needed. In healthy older adults most sensory and consumer methods can be applied (Methven et al., 2016). However the use of consumer tests with this segment of population should be evaluated carefully, due to the possible presence of difficulties related to the comprehension and use of rating scales (Dermiki et al., 2013) and cognitive and perceptive fatigue with long and complex methodologies. A methodology with big potential, yet to be fully explored with older adults is the Free sorting task. Considering these aspects, the study of usability of Free sorting task among healthy older adults would be of interest. This issue was explored in Study II, where older adults from Italy and France were involved in a Free sorting task with peas and sweetcorn samples. Among the different approaches to investigate eating behaviour, the use of interviews and questionnaires may be considered as the most common one, thanks to their relative low cost and ease of submission. However, explicitly measured concepts may suffer from limitations such as voluntary self-presentation strategies (e.g. social desirability), resulting in a discrepancy between declared and actual behavior (Maass et al., 2000). Implicit measurements (De Houwer & Moors, 2010) may overcome some of the problematic elements of traditional self-report measures of attitudes. The use of both explicit and implicit measurements, such as the Implicit Association Test, may therefore be an effective approach to classify with higher reliability consumers’ attitudes toward the vegetable category. This issue was explored in Study III, where vegetarians, flexitarians and omnivores were involved in an Implicit association test intended to assess their attitudes toward plant-based and animal-based dishes and the physiological and psychological variables that may influence these attitudes. Study I concluded that specific dishes, such as salads and boiled vegetables, were more typical of the plant-based dish category than others, such as soups and fried vegetables. Typicality affected expected liking for dishes depending on the consumers’ level of familiarity toward vegetables. Among consumers with a low level of familiarity toward vegetables, the less a dish is typical the higher the expected liking is. No similar relation was found among consumers with a high level of familiarity. Expected sensory attributes were found to influence the typicality of a dish. The attributes Bitter, Green and Bland positively influenced typicality, while Brown, White and Creamy negatively influenced it. The promotion of consumption of vegetables targeted at vegetables dislikers should therefore consider their representation of the category, in order to limit the exposure to features with a negative hedonic value. Study II concluded that the Free sorting task was a suitable method to use with healthy older adults, as it allowed the detection of differences in the categorization of stimuli even among the more aged representatives of the elderly population. Familiarity with the product was the main factor affecting the categorization maps of the tasted vegetables. Categorization maps from the familiar vegetables were found to be reliable to obtain information on sensory and hedonic dimensions, while maps obtained from the unfamiliar vegetables mainly depicted sensory variability. Study III concluded that the Implicit association test is an effective method to study attitudes toward the plant-based dish category. Vegetarians and Flexitarians were more inclined to implicitly associate positive emotions to meat-free dishes than omnivores, with vegetarians showing a stronger association than Flexitarians. Our findings showed that positive attitudes toward meat-free dishes were positively related to the empathic sensitivity toward humans and animals and positive attitudes toward healthy and natural products, whilst being negatively related to bitter responsiveness and sensitivity toward pathogen disgust. Conversely food pleasure emerged as equally important among the considered groups, highlighting a higher importance of food consciousness in determining the eating habits considered. In conclusion, all the methodological approaches considered in this research proved able to satisfy the different research questions related to the study of the preference for vegetables, therefore confirming the effectiveness and reliability of categorization in consumers’ studies.