Sustainable valorization of oak acorns as a potential source of oil rich in bioactive compounds

Abstract

Abstract The acorns (fruits) of the oak species Quercus rubra L. and Quercus robur L., grown over the world mainly in forests and parks, are usually not collected or utilised, therefore represent a potentially cheap/free source of plant material with potential applications in the processing industry. In the present study, oil recovery and composition from acorns collected from Q. rubra (n\xa0=\xa06) and Q. robur (n\xa0=\xa07) individuals was evaluated. Oil yields from Q. robur and Q. rubra acorns ranged from 3.1 to 6.3% and 20.1–24.0%, respectively. In the oils of both species C18:1 (28.4–65.7%), C18:2 (24.1–48.0%) and C16:0 (7.5–17.9%) were the main fatty acids with some differences in proportions between species. On average, β-sitosterol constituted 64.3% and 68.1% of total sterol concentration, which amounted to 244.9 and 271.4\xa0mg/100\xa0g oil in Q. robur and Q. rubra, respectively. Q. rubra acorn oil was rich in β-tocopherol (93%), while Q. robur in γ-tocopherol (96%). A nearly six-fold higher level of total tocopherol content was recorded for Q. robur relative to Q. rubra. Principal component analysis of chemical composition data confirmed their ability to distinguish between Q. robur and Q. rubra samples. The unique and high concentration of lipophilic compounds in both species, and the availability (cheap/free) of acorns, make oak fruits an interesting source of plant material for industrial applications.