Using controlled environment agriculture to improve the sensory quality and consumer acceptance of baby leafy greens
Creators: name: O'Brien, Regina Michael
Publisher: name: No Publisher Supplied
Year: 2022

description: Baby leafy greens are an agricultural commodity currently in high demand. Controlled Environment Agriculture (CEA) is one method of commercially growing baby greens aimed at supplying consistent, locally grown product by technology-based monitoring and manipulation of the growing environment. Plants from the family Brassicaceae are particularly important to the industry and to human health, however the presence of sulfur-containing compounds including glucosinolates and isothiocyanates are assumed to contribute to the potentially unpalatable bitter taste and pungency associated with cruciferous vegetables. These phytochemicals can be increased through environmental stress applied during growth; however, the sensory effects of these changes have not been documented. Further, the consumer appeal of these varieties, especially the impact of visual cues at the time of purchase are not well understood.The first aims of this dissertation were to develop a lexicon for a variety of Brassicaceae and non-Brassicaceae baby leafy greens, comparing traditional descriptive analysis (DA) evaluations to the rapid-profiling method Napping using trained panelists. The second aim was to understand the role of environmental stress on the sensory attributes and phytochemical profiles of Brassicaceae grown in a commercial CEA farm. The third aim was to understand drivers of consumer liking for varieties of leafy greens with a range of sensory profiles, and to understand how visual information (i.e., appearance, descriptors, and labeling information) influences purchasing behavior for leafy greens. This dissertation is divided into three sections.In the first section, a sensory panel (n=11) trained in traditional Descriptive Analysis (DA) developed a lexicon to evaluate sensory characteristics of twelve commercially available baby greens. The results were compared to the Napping profiling method to determine if it could be applied to the same samples. In the DA evaluation, all varieties were discriminated by pungent attributes and green quality. Principal component analysis (PCA) was used to model associations between the samples and the sensory attributes. Significant differences between all sensory attributes except for Overall Green Aroma were found. The PCA extracted three factors. PC1 ranged from pungent qualities to sweet/grassy, PC2 included green color, and PC3 included saltiness and sourness. The Napping showed similar sample discrimination (RV = 0.67), but included relevant textural terms (‘‘chewy’’; ‘‘rubbery’’) not used in the DA.In the second section, trained panelists (n=11) evaluated three Brassicaceae plants grown under environmental stress during growth, including blue light application, light intensity application, sulfur manipulation, and nitrogen reduction. Variety- and environment-dependent changes to the sensory profiles were seen, with most changes resulting in increases to pungent attributes such as sulfur, bitterness, heat, and nasal pungency. Leaf color and size were also affected by the stressors. The Principal Component analysis extracted three factors: F1 included pungent attributes, F2 included green attributes, and F3 included astringency, bitterness and earthy-green. Samples were primarily grouped by variety and experiment. Distinct sensory profiles were determined for arugula as a function of (blue) light manipulation, for mustard green as a result of nitrogen reduction, and for red kale as a result of sulfur manipulation, all at 95% confidence. Chemicals associated with pungency included 4-methylpentyl ITC, glucocheirolin, and total GSLs.In the third section, participants (n=73) evaluated six baby greens grown with CEA and rated their liking for the aroma, flavor, texture and overall liking of each sample. Significant differences were found between samples for all attributes except aroma. Overall, participants liked greens with sweeter flavor. Agglomerative Hierarchical Clustering was used to segment consumers. Three groups were observed with differences in liking; differences were observed for all samples except Red Romaine lettuce. To understand purchasing behavior with respect to appearance and flavor, an online survey (n=397) was conducted using choice-based conjoint analysis (CBC), and consumers were segmented using k-means clustering. The CBC revealed different consumer groups who placed importance on different sensory attributes: one group which preferred flat, green-colored leaves, one which preferred sweet greens, one which preferred mixed color and leaf texture, and one which preferred spicy flavor. Differences between clusters were observed for gender, income, and bitter food liking.This dissertation presents important findings for the agricultural industry. To our knowledge, this is the first lexicon for baby leafy greens that can be broadly applied to both Brassica and non-Brassica species. It was demonstrated that the use of the rapid profiling method Napping could sufficiently discriminate the samples and may be warranted as an alternative to DA in this context. These strategies can be used to differentiate potential new baby greens for the marketplace. Second, we determined that environmental stressors during growth impact the sensory characteristics of baby leaves, however, the effects of the stressors on the sensory characteristics were not systematic and reflected specific variety-environment interactions. Further work in this area will ultimately lead to design strategies to produce baby greens tailored for specific consumer groups. Novel findings identified associations between phytochemicals and sensory attributes not previously characterized. Finally, two methods of consumer testing revealed a similar pattern in liking for diverse sets of consumers. Results from this research can be used to inform the cultivation practices and marketing of baby leafy greens and to better understand consumer preferences for these products.