Since truffles are quite expensive, truffle oil sold in stores is often “fake” or fortified with cheaper truffle varieties and/or natural flavors so that it can still have “truffles” in the name. In contrast to many other oils, truffle oil is not produced by means of pressing; instead, the truffles are soaked in oil until the oil takes on a truffle flavor.
From Wikipedia: “Truffle oil is a modern culinary ingredient used to impart the flavor and aroma of truffles to a dish. ... Truffle oil is available in all seasons and relatively steady in price. ...
Truffle oil is controversial as a flavoring ingredient, as some truffle oil is artificially produced and may lack the complex flavors and aromas of fresh truffles.”
Culinary uses of Truffle oil:
“The ingredient is commonly used as a finishing oil in a variety of dishes, including truffle fries, pasta dishes, pizzas, and puréed foods such as mashed potatoes and deviled eggs.”
“Truffle oil is used as a lower-cost and convenient substitute for truffles, to provide flavoring, or to enhance the flavor and aroma of truffles in cooking. Most "truffle oil", however, does not contain any truffles. The vast majority is olive oil which has been artificially flavoured using a synthetic agent such as 2,4-dithiapentane.”
Culinary uses of truffles:
“Because of their high price and their pungent aroma, truffles are used sparingly. Supplies can be found commercially as unadulterated fresh produce or preserved, typically in a light brine.
White truffles are generally served raw, and shaved over steaming buttered pasta, salads, or fried eggs. White or black paper-thin truffle slices may be inserted into meats, under the skins of roasted fowl, in foie gras preparations, in pâtés, or in stuffings. Some speciality cheeses contain truffles, as well.
The flavor of black truffles is far less pungent and more refined than that of white truffles. Their strong flavor is often described as syrupy sweet. Black truffles also are used for producing truffle salt and truffle honey.
While in the past chefs used to peel truffles, in modern times, most restaurants brush the truffle carefully and shave it or dice it with the skin on so as to make the most of this valuable ingredient. A few restaurants in Switzerland still stamp out circular discs of truffle flesh and use the skins for sauces.”
“The bulk of truffle oil on the market is made with a synthetic ingredient, as are many other truffle products. However, alcohol is now being used to carry the truffle flavour without the need for synthetic flavourings. The first truffle vodka, Black Moth Vodka, is a natural vodka infused with black Périgord truffles (Tuber melanosporum). Although primarily used as a spirit in its own right and mixed in a range of cocktails, truffle vodka is also used by various chefs to flavour dishes by evaporating the alcohol through cooking whilst retaining the truffle aroma.”
Recipe for making truffle oil:
Clean 10 g of truffles and use a slicer to cut into very thin slices. Add to a sterilized bottle, along with 100 ml vegetable oil (e.g., canola, safflower, or sunflower oil) and close tightly. Store the oil in a cool and dark place. After about a week, the oil will have taken on the flavor of the truffles and be ready to use. You can remove the truffle slices and use them for other dishes. The oil can be stored in the refrigerator for up to a year.
“It is popular with chefs, home cooks, and diners because it is significantly less expensive than fresh truffles. This has also led to a market "growing" in the product and an increase in the availability of truffle-flavored foods.”
“Artificial truffle oils have been produced since the 1980s, around when truffles became internationally popular.”