Physicochemical Characteristics of Cold-Pressed Hemp, Flax, Hazelnut, and Pumpkin Seed Oils and Press Cakes

The physicochemical characteristics of cold-pressed hemp, flax, hazelnut, and pumpkin seed oils, along with the valorization opportunities of press cakes, were investigated. Initially, cold-pressed oils were analyzed for their yield, total fat content, acylglycerol composition, fatty acid compositions, and oxidative stability. In addition to analyzing the oils, the press cakes were also evaluated. Specifically, we assessed their fiber content, fatty acid, and amino acid profile. The oil yield of the seeds ranged from 20.62% to 54.07%, with hazelnut seeds recording the highest level. The acylglycerol composition of the oils showed low quality for commercial purposes in terms of partial hydrolysis of the oils (4.34%–17.08% free fatty acids and 3.68%–11.59% diacylglycerol). The highest percentage of total unsaturated fatty acids was recorded for hazelnut (92.47%), followed by flax (90.95%) and hemp (90.03%), and the highest degree of polyunsaturated fatty acids belonged to flaxseed oil and hemp seed oil (76.40% and 76.00%, respectively). The induction period of cold-pressed oils ranged between 3.29 and 17.30 h, with hazelnut oil being the most stable one. Additionally, the press cakes demonstrated significant potential as a source of dietary fiber (16.50%–34.94%), protein (26.49%–44.50%), and oil (6.45%–34.69%). The fatty acid and amino acid composition of press cakes showed that they can be a valuable source of essential amino acids (8.96%–15.00%).

Practical Applications: The research not only provided valuable insights into the physicochemical properties of cold-pressed oils but also emphasized the significant potential of their by-products, the press cakes, within the food industry.