Optimization of hemp seed oil extraction and functional testing of its by-product in gluten-free baked goods

Hemp is a non-psychoactive variety of cannabis. Its seed is rich in high quality protein, dietary fiber, and polyunsaturated fatty acids (PUFA). Oil extraction can be performed by cold pressing, and the by-product, known as press cake, is an interesting matrix to formulate functional foods. Response surface methodology was used for the optimization of hemp seed oil extraction by means of cold pressing. Experiments were carried out according to a face-centered central composite design with two independent variables (press and roasting temperature) at three different levels (60 °C, 65 °C, 70 °C; 120 °C, 140 °C, 160 °C). Optimized conditions were determined by a press temperature (PT) of 68.6 °C and a roasting temperature (RT) of 159.5 °C, with a predicted oil yield of 40.77% and an experimental one of 45.59%. With a circular economy approach, the by-product of the extraction process was used in the development of functional gluten free cookies, a source of protein and fiber, as well as antioxidant compounds. The cookie with higher press cake substitution showed the best results with a total phenolic content (TPC) after in vitro digestion of 3.97 ± 0.13 mg GAE/g and an antioxidant capacity measured by 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Ferric Reducing Antioxidant Power (FRAP) methods of 103 ± 4 µmol TEQ/g and 29 ± 1 µmol TEQ/g.