Oils differ for several reasons: firstly, it depends on the method of extraction. Oils produced by mechanical means, not using chemical solvents are called virgin. Olive oils are basically Virgin.
Virgin olive oils are classified and differentiated by their quality parameters.
Unlike other oils, Extra Virgin olive oil presents the best quality indexes, both physical-chemical and sensory.
Virgin olive oil may show small alterations in its quality parameters, both physical-chemical and sensory. It is therefore a lower quality oil compared to extra virgin.
Finally Lampante Virgin olive oils have suffered an alteration in their quality parameters and mustn´t be packaged and sold to the public, so they shall be refined industrially.
Which are not sold packaged and when mixed with Virgin olive oils produce olive oil. They are industrially prepared with great continuity of flavor, but which may lack some elements of nutritional interest in extra virgin olive oils.
The last of oils in markets is the olive pomace oil. It comes from the refining of pomace oil crude, obtained by treating olive pomace with organic solvents. It has a similar composition to olive oils but of lower quality, yet really suitable for frying, even better than any seed oil.
Because Extra Virgin is the olive juice from healthy fruits gathered in their ideal moment of ripeness, under special conditions so its properties wouldn´t be altered. Containing all the minority components of nutritional interest as well as an extraordinary composition in fatty acids, it offers a great variety of sensory nuances that make it unique among oils and suitable both for consuming it raw and any other culinary uses. It is one of the essential elements in the Mediterranean diet.
Acidity, measured in oleic acid, is the amount of free fatty acids, expressed in this acid. It is the measure of an alteration, by hydrolysis of the triglycerides in oil. It is also an expression-but neither the only nor the most important one, of an alteration in the quality of oil. It is used, along with other parameters, to classify Virgin oils in three categories, Extra, Virgin and Lampante.
Extra virgin olive oil is the best oil for frying and for any other culinary use as well. On some occasions, when extra virgin olive oils have especially marked sensory features, or a flavor not associated to Extra Virgin is preferred when frying, then plain olive oil can be used with excellent results instead.
Time finally alters each and every oil, especially through oxidation, getting rancid after a long storage period. Use time depends on several factors such as the variety, the type of oil… Extra virgins are, in general, more resistant than plain olive oils, and of course, storage both in warehouses and private homes, etc. Therefore each oil must have a “best by” date printed. Oils should be consumed within the preferential consumption period.
These lumps are triglycerides from saturated fatty acids that solidify at a higher temperature than the rest of triglycerides, producing those small beads at the bottom of the bottle. These lumps or beads disappear when temperature increases, even the whole oil might solidify at lower temperatures. This behavior is normal and does not involve any problem unless an exceeding wax percentage would be discovered during chemical analysis, but generally, it is irrelevant.
The colour of extra virgin olive oil has no importance on the quality of it. The colour is not a quality parameter. Therefore any colour from green to yellow gold oil may have similar qualities. However, there may be a preference by consumers, it is a hedonistic preference, either by preferences or to decorate a particular dish, but never the colour of the oil must be related to quality.
It depends on the type of oil you use. Olive oil can be reused more times than seed oils due to its thermal oxidation resistance. The type of the product fried and the frying conditions also affect the number of reuses.
You can reheat oil more times if you fry chips better than anything rolled in breadcrumbs.
There are devices to measure the percentage of polar compounds during the frying process. Oil to be reused must have these components below the estimated limit.
There is no objection to mix different types of oil. Yet it is not advisable to mix extra virgin olive oil with other types since its quality will definitely diminish.
It should not be poured down the drain. There are large companies in big cities removing that oil to be industrially recycled. Try to contact such companies or your own Local Administration.
Not necessarily. It depends on other alimentary factors.
Expired oil should not be used, since its quality parameters may likely be altered and it might get rancid.
Today first press olive oil has virtually disappeared, since it is made in continuous centrifugal presses. It is wrong to believe that murkier and thicker oil is best. The appearance has nothing to do with the quality of the oil. Today, the extra virgin is considered the best oil, since the olive paste is never heated above 27ºC during the extraction.
Pomace oil is obtained from the by-product of the olive oil extraction process, that is, by organic solvent extraction-once dried, of the residual oil from the remaining press cake. Subsequently, this oil is refined and later mixed with virgin olive oil and the blended product, the olive pomace oil, is fit for consumption.