Beech (Fagus sylvatica L.) Kernels as a Sustainable Alternative in Oil Production—Influence of Processing and Extraction Techniques on the Physico-Chemical Profile

Beech (Fagus sylvatica L.) kernels are a sustainable plant material suitable for human consumption. This study analyzes the impact of moistening and roasting (thermal treatment) beech kernels on the development of novel edible oils. Crude beech kernels (CBKs) and thermal-treated beech kernels (TTBKs) were analyzed for their chemical and bioactive compound compositions to assess the influence of thermal treatment prior to different extraction methods (cold pressing, cold solvent extraction—Folch, and hot extraction—Soxhlet). The predominant phenolic compounds found in beech kernels belong to the flavanol group, with the most abundant being kaempferol-rutinoside (773.34 µg/g in CBK and 714.77 µg/g in TTBK). Lutein was the most significant carotenoid present in the oils (384.80 µg/g in crude oil and 456.21 µg/g in thermal-treated oil), and its concentration increased due to kernel conditioning. Thermal treatment had a minimal impact on the overall fatty acid composition, while the majority of these acids are predominantly mono- and polyunsaturated. Cold-pressed oils have higher viscosity than oils extracted using Folch’s technique. Overall, beech kernels represent a sustainable plant material, while seed conditioning through moistening and roasting enhanced bioactive compound transfer to extracted oils.