OIL AND FAT: OLIVE OIL
Diagram
Two olive oils from the same fruit
Extra virgin olive oil
Olives pressed by mechanical means only, with no heat and no chemical refining. Keeps its flavour, colour and aroma.
↓
Refined olive oil
Olive oil that has been refined with heat and processing to remove flavour, colour and defects. Neutral in taste.
Figure 1: Extra virgin oil is pressed from olives with no refining, while refined oil is processed until it is neutral. Drawn in our own style from the olive oil discussion in The Extra-Virgin Olive Oil Handbook and in Gunstone, Vegetable Oils in Food Technology.
Introduction
Extra virgin olive oil and refined olive oil both come from olives, and both sit in similar bottles on the same shelf, but they are made in different ways. Extra virgin olive oil is obtained from olives by mechanical pressing only, with no heat and no chemical treatment, so it keeps the flavour, aroma and colour of the fruit. Refined olive oil starts as an oil that cannot be sold as it is, usually virgin oil with defects, and it is refined with heat and processing to remove flavour, colour and free fatty acids, so the finished oil is neutral in taste.
Quick comparison
Table 1: Extra Virgin Olive Oil compared with Refined Olive Oil
| Aspect | Extra Virgin Olive Oil | Refined Olive Oil |
|---|---|---|
| Source | Olives, pressed by mechanical means only | Olives, from oil that needed refining |
| How it is made | Crushing and pressing, with no heat and no chemicals | Refining with heat and processing, including neutralising and deodorising |
| Flavour | Fruity, with the flavour and aroma of fresh olives | Neutral, with little flavour or aroma |
| Colour | Green to golden, from the fruit | Pale, because refining removes colour |
| Free fatty acids | Low, because only sound olives pressed cold give extra virgin grade | Low after refining, because neutralising removes free fatty acids |
| Smell | Fresh olive aroma | Almost no smell |
| Use in cooking | Dressings, dipping and finishing, where flavour matters | Frying and general cooking, where a neutral oil is wanted |
| Heat | Best used without long high heat, so its flavour is kept | Suited to higher heat cooking because it is neutral and refined |
| Price | Higher, because the yield is lower and only sound fruit qualifies | Lower, because refining recovers oil that could not be sold as it was |
| What refining removes | Nothing is removed: the oil is used as pressed | Flavour, colour, odour and free fatty acids are removed |
Scientific explanation
Definition
Extra virgin olive oil is the oil obtained from olives by mechanical means only, without heat and without chemical treatment, and it is the highest grade of olive oil. Refined olive oil is olive oil that has been refined to remove defects of flavour, colour, odour and acidity, and it is neutral in flavour. The Extra-Virgin Olive Oil Handbook states that extra virgin oil has a superior level of health properties and flavour compared with virgin and refined olive oils.
Working principle
Extra virgin oil is made by crushing olives and pressing out the oil, then separating the oil from the water and solids. Because no heat and no chemicals are used, the compounds that give flavour and aroma stay in the oil. Refined oil is made by taking olive oil that has defects, then refining it: the oil is neutralised to remove free fatty acids, bleached to remove colour, and deodorised with steam to remove odour. Each refining step strips out flavour compounds as well as defects, so the finished oil is bland. Refined oil is often blended with a little virgin oil to give it some flavour.
Apparatus
The books used here name no laboratory apparatus for measuring or comparing either term, so no apparatus list is given.
Measurement procedure
The books used here give no standard laboratory procedure with volumes and steps for either term, so no procedure is invented here.
Factors affecting readings
For extra virgin oil, the quality of the olives, the time between picking and pressing, and the pressing temperature decide the flavour and the acidity: damaged or late-pressed olives give oil with defects that cannot be sold as extra virgin. For refined oil, the refining conditions decide how much flavour and colour remain: stronger refining gives a more neutral oil. Storage matters for both: light, heat and air spoil olive oil, and extra virgin oil loses its fresh flavour first because its flavour compounds are the ones that fade.
Formulas and calculations
The books used here give no formula for either term, so no formula is given here.
Industrial applications
- Extra virgin olive oil: salad dressings, dipping and finishing dishes, where its olive flavour is the point.
- Extra virgin olive oil: dressings and sauces that are not heated for long, so the flavour survives.
- Refined olive oil: frying and roasting, where a neutral oil that tolerates heat is wanted.
- Refined olive oil: general cooking and food manufacture, where the oil must not add flavour of its own.
- Refined olive oil: blended with virgin oil to make a mild cooking oil with a little olive flavour.
Advantages and limitations
- Extra virgin olive oil, advantage: it keeps the flavour, aroma and colour of fresh olives, and the handbook notes its superior flavour and health properties.
- Extra virgin olive oil, limitation: it costs more, and its flavour is lost if it is heated hard for a long time.
- Refined olive oil, advantage: it is neutral, lower in price, and suited to frying and general cooking.
- Refined olive oil, limitation: refining removes the flavour, aroma and colour that make olive oil distinctive.
FAQ
What is the main difference between extra virgin and refined olive oil?
Extra virgin oil is pressed from olives with no heat and no chemicals, while refined oil is processed with heat and refining to remove flavour, colour and defects.
Which one tastes of olives?
Extra virgin olive oil tastes of olives. Refined olive oil is neutral and tastes of almost nothing.
Can refined olive oil be used for frying?
Yes. Its neutral character and refining make it suited to general cooking and frying, where extra virgin oil would lose its flavour.
Why is extra virgin olive oil more expensive?
Only sound olives pressed by mechanical means qualify, the yield is lower, and no refining step recovers defective oil.
Is refined olive oil still olive oil?
Yes. It comes from olives, but it has been refined, so it has lost the flavour, colour and aroma of the pressed oil.
References and further reading
- FTN books on disk: Technology of Fats and Oils.
- The Extra-Virgin Olive Oil Handbook (extra virgin oil has a superior level of health properties and flavour compared with virgin and refined olive oils).
- Gunstone, Frank. Vegetable Oils in Food Technology. Wiley, 2011.
- Google Books pages read for this article:
- O’Brien, Richard D. Fats and Oils: Formulating and Processing for Applications. 3rd ed., CRC Press, 2008 (Google Books page read)
