Extraction, chemical components, bioactive functions and adulteration identification of walnut oils: A review

Walnut oil is a functional wood oil known to researchers that may potentially be a large source of Chinese edible oils. There are various extraction methods for walnut oil, including traditional (pressing, solvent- and enzyme-assisted extraction) and novel methods (microwave, ultrasound, supercritical CO₂, subcritical and other extraction technologies). Walnut oil is rich in nutrients, including phytosterols, tocopherols, polyphenols, squalene and minerals. It provides many health benefits, such as antioxidant, antitumor, anti-inflammatory, antidiabetic and lipid metabolism-related functions. In addition, the authentication of walnut oil has received much research attention. The present review provides detailed research on walnut oil extraction, composition, health benefits and adulteration identification methods. The path toward further walnut oil improvement in the context of the market value of walnut oil is also discussed.