The biological role of glucosinolates and isothiocyanates in rucola, and the effects on sensory quality traits
Luke Bell (University of Reading)Natasha Spadafora (Cardiff University)Lisa Methven (University of Reading)Carsten Müller (Cardiff University)Maria Jose Oruna-Concha (University of Reading)Hilary Rogers (Cardiff University)Carol Wagstaff (University of Reading)
Rucola (rocket; Eruca & Diplotaxis spp.) are leafy salad crops that contain glucosinolates (GSLs) and various other interesting phytochemicals. GSLs and their hydrolysis breakdown products are utilised in plant defense against pathogens and pests, but are also known to be the cause of strong, pungent, and bitter tastes and aromas. Some of these compounds are very efficacious at deterring pests and disease, but are also repellant to many consumers. Most focus on quality has previously been given to visual traits – in our work we have focused on quality phytochemical traits, such as maximizing heath beneficial compounds (GSLs, isothiocyanates (ITCs), and flavonols) but also assessing how these compounds affect sensory attributes, and in turn, the ‘quality’ of the eating experience. Six accessions of germplasm rucola and one commercial variety were selected for assessment of such quality traits to determine their potential for introduction into plant breeding programs. GSLs and flavonols were analysed by LC-MS, volatile compounds by GC-MS, and sugars by capillary electrophoresis. The cultivars were also tested in controlled sensory evaluations by a panel of ten, highly trained sensory analysts. Data from sensory and technical analyses were combined using Principal Component Analysis (PCA) to determine significant correlations between sensory traits and chemical compounds. It was found that a large amount of variation exists between cultivars of rocket, and the levels of bitterness, pungency, and sweetness are largely due to differences in GSL/ITC profiles and the ratio of these compounds with sugars.