Olive oil, other oils and culinary fats: composition, quality, storage, cooking uses and how they differ.
Yes. Extra-virgin olive oil can be used for frying. Its monounsaturated-fat profile and natural antioxidants give it good heat stability. UC Davis reports smoke points for olive oils of roughly 347–464°F (175–240°C), depending on grade, quality and freshness, which overlaps normal frying temperatures. Control the heat and do not deliberately let the oil smoke.
Olive-oil acidity is a laboratory measure of free fatty acids, conventionally expressed as grams of oleic acid per 100 g of oil. It is not pH and it does not directly measure sourness. Under international and EU standards, extra-virgin olive oil has a maximum free acidity of 0.8 g/100 g; virgin olive oil can be up to 2 g/100 g.
Olive-oil acidity is not something you taste the way you taste lemon acidity. It is a laboratory measurement of free fatty acids. Fruitiness comes from volatile aroma compounds, while bitterness and much of the peppery sensation are linked to phenolics. A very pungent extra-virgin oil can therefore have extremely low free acidity.
Store olive oil tightly closed in packaging that limits light and in a cool, stable place away from the range, oven and sunny windows. Oxygen, light and heat all accelerate oxidation. Buying a bottle size you can finish at a reasonable pace also helps because a large half-empty bottle spends more time exposed to headspace oxygen.
Refrigeration is not required for everyday olive-oil storage. Lower temperatures can slow oxidation, but they can also cause waxes and some triglycerides to crystallize, making the oil cloudy or partly solid. That physical change usually reverses as the oil warms. For regular use, a cool dark cabinet is usually the easier choice.
Olive oil does not flip from good to dangerous on a single date, but it does age. Over time oxidation reduces fresh aroma and eventually creates rancid flavors; opening the bottle speeds exposure to oxygen. Treat the best-by date as a quality reference and replace oil that smells or tastes clearly stale, waxy or rancid.
Bitterness and pungency are not the same sensation. Bitterness is a taste perceived in the mouth; pungency is a biting tactile sensation often most obvious in the back of the throat. The International Olive Council recognizes both as positive attributes of virgin olive oils, and their intensity is influenced by different parts of the oil's phenolic profile.
Bitterness in virgin olive oil can be completely normal. The International Olive Council recognizes it as a positive attribute, especially in oils from green or turning-color olives. Intensity is linked to the phenolic profile, with oleuropein- and ligstroside-derived compounds playing important roles. Bitter does not mean rancid.
Light and heat speed the reactions that oxidize olive oil. Over time, fresh aromas and protective phenolic compounds decline and rancid notes develop. Store the oil tightly closed, protected from light and away from stoves, ovens, sunny windows and other sustained heat sources.
Cold olive oil can turn cloudy, form flakes or partially solidify because its waxes and triglycerides do not all crystallize at the same temperature. As the oil gradually warms, those crystals melt again. The change is normal and the refrigerator test is not a reliable measure of purity or quality.
The throat sting in many virgin olive oils, especially fresh oils from greener fruit, is normal and can be a positive sensory attribute. Oleocanthal is one compound involved: it activates TRPA1 sensory receptors and creates a distinctive pharyngeal pungency. It is not the same thing as the oil's free-acidity number.
Olives are a fatty fruit rather than a sugary one. A current USDA green-olive reference provides about 145 calories, 15.3 g fat, 3.3 g fiber and 1,556 mg sodium per 100 g. In a 30 g serving, that is about 44 calories, 4.6 g fat, 1.0 g fiber and roughly 467 mg sodium. Sodium is the number most likely to vary substantially among brands and curing styles.