Biotechnological Valorisation of Oilseed Cakes in the Formulation of Vegan Yoghurt-like Fermented Beverages

The sustainable valorisation of agro-industrial by-products offers a promising pathway to address global protein demand while supporting circular food systems. This study explored the biotechnological potential of pumpkin (Cucurbita pepo), sunflower (Helianthus annuus), and walnut (Juglans regia L.) oilseed cakes as substrates for developing vegan yoghurt-like fermented beverages. Each formulation was fermented with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, and comprehensively evaluated for composition, functionality, sensory properties, and bioactivity. The oilseed-based beverages exhibited protein levels between 3.7–4.6%, fibre content up to 1.9%, and reduced syneresis (14–18%) compared with the commercial almond-based product (21.5%). The walnut-based variant (WOCY) showed the highest total polyphenol content (1108.97 mg GAE kg−1) and antioxidant activity (412.54 mg Trolox kg−1 DPPH; 51.5 mg TE g−1 DW ABTS), surpassing both the almond-based vegan yoghurt (238.82 mg GAE kg−1) and dairy reference (96.10 mg GAE kg−1). Preliminary sensory profiling through the Check-All-That-Apply (CATA) method indicated that pumpkin- and walnut-based samples were most associated with “creamy texture,” “nutty aroma,” and “very pleasant” descriptors, achieving acceptance comparable to or higher than conventional yoghurts. Microbiological analyses confirmed product safety and high viable cell counts (<108 CFU mL−1) after 14 days of storage. Oilseed cakes serve as efficient substrates for producing nutrient-dense, antioxidant-rich, and sensorially appealing plant-based fermented beverages, supporting functional food innovation and promoting circular bioeconomy through the sustainable valorisation of agro-industrial by-products.