Hazelnut oil is an oil pressed from hazelnuts. Cold-pressed hazelnut oil will be a light golden brown; hazelnut oil pressed from roasted hazelnuts will be a nutty brown colour, and have a very pronounced, strong flavour of hazelnuts.
It is very popular in France as a finishing oil.
Hazelnut oil and food fraud
Cheaper hazelnut oil coming from Turkey has been used as an adulterant in olive oil to commit food fraud:
“Hazelnut oil adulteration of olive oil is… a genuine authenticity issue, as evidenced by a carefully documented episode in which over 20 000 tonnes of Turkish hazelnut oil was shipped to Northern Europe as sunflower oil, with much of it then being transported in French trucks to Spain, where it was mixed in proportions of 15–50% with olive oil, before being sold on to Spanish production and bottling facilities as olive oil.” Parker, T., et al. “60MHz 1H NMR Spectroscopy for the Analysis of Edible Oils.” TrAC Trends in Analytical Chemistry, vol. 57, 2014, pp. 147–58. Crossref, doi:10.1016/j.trac.2014.02.006.
It can take very close lab analysis using spectroscopy to detect the presence of hazelnut oil in olive oil: “It is difficult to discern differences between the oil types simply by visual inspection. However, closer scrutiny of certain spectral regions reveals clear, systematic differences between olive oils and hazelnut oils.” Ibid.
Use hazelnut oil as a flavouring or “finishing” oil rather than a frying oil. Use it in very small quantities so that the flavour isn’t overwhelming.
It will smoke in the range of 221 C (430 F) — but it’s too expensive to cook with, anyway.
Low in saturated fat, rich in Vitamin E.
The “fatty acid composition [of hazelnut oil] is very similar to that of olive oil.” If anything, “hazelnut oils typically contain slightly more unsaturated fatty acids than olive oils.” Ibid.
Refrigerate after opening; if it becomes thick, just set out for an hour or two before needed.