Preparation and quality evaluation of coffee substitutes based on milk thistle ( Silybum marianum L.) seeds

In this study, we developed and evaluated novel plant-based coffee substitutes produced from light- and dark-roasted milk thistle ( Silybum marianum L.) seeds. The seeds exhibited a suitable composition for coffee substitute production, containing moderate protein (18.50%) and oil (14.58%) contents with low moisture (5.85%). Roasting significantly affected the color, moisture content, and volatile aroma profile of the ground products. However, the brewed beverages showed similar physicochemical properties, including soluble solids (1.2 °Brix), pH (6.45–6.46), viscosity (1.43–1.45 cP), and ash content (0.05%), indicating limited effects of roasting intensity on beverage quality. Forty volatile compounds were identified, with pyrazines, furans, pyrroles, phenols, and ketones predominating. Dark roasting enhanced the formation of pyrazines and furans, producing a more pronounced roasted aroma. Sensory evaluation identified roasted, nutty, spicy, and bitter attributes as dominant, together with distinctive herbal and cardamom-like notes characteristic of milk thistle seeds. Consumer testing demonstrated good overall acceptability for both beverages, with a slight preference for the light-roasted sample. These findings demonstrate the potential of roasted milk thistle seeds as a novel caffeine-free, plant-based coffee substitute with distinctive sensory characteristics and promising consumer acceptance.