Question 1

What do the different olive oil grades mean?

Accepted Answer

The grades describe how the oil was extracted and how much it has degraded — not, as many assume, how the olives were pressed or how many times.

**Extra virgin** is the top grade. It is mechanically extracted without heat or chemical solvents, and must meet two standards: free acidity no higher than 0.8%, and no detectable sensory defects when assessed by a trained tasting panel. That second requirement is unusual — the grade depends partly on a taste test, not only on chemistry.

**Virgin** is also mechanically extracted, with acidity up to 2% and minor sensory defects permitted. Less common on shelves.

**Refined olive oil** is virgin oil that failed the grade and has been treated with heat, filtration or chemicals to strip out the defects. This removes flavour and much of the aromatic content along with the faults.

**Olive oil** or **pure olive oil** on a label usually means refined oil with a little virgin blended back in for flavour.

**Olive pomace oil** is extracted with solvents from the residue left after pressing. It is the lowest grade and is generally used industrially.

"Cold pressed" and "first cold pressed" are largely marketing on modern oils. Almost all extra virgin oil is now made by centrifuge rather than pressing, and temperature limits are already implied by the extra virgin grade.

On cooking with it: the claim that extra virgin cannot be heated is overstated. Its smoke point is around 190–207°C, above most domestic frying, and its antioxidants make it comparatively stable. The real argument for using cheaper oil in high-heat cooking is cost, since the delicate flavour is destroyed either way.

Store it dark and cool; light and heat degrade it faster than age.

Question 2

Why does cooking oil go rancid, and how should you store it?

Accepted Answer

Rancidity is the chemical degradation of fats, producing the stale, waxy, crayon-like smell and taste of an old oil. There are two distinct mechanisms, and the storage advice follows from them.

Question 3

What is a smoke point, and does it matter as much as people say?

Accepted Answer

The temperature at which an oil begins to break down visibly and produce smoke. It is a useful rough guide and a poor single measure of which oil to cook with, because it is neither fixed for a given

Question 4

What do E numbers and food additives actually do?

Accepted Answer

An E number is simply a code indicating that an additive has been assessed and approved for use in the EU and UK. It is a mark of regulatory evaluation, not a warning — which is the opposite of how

Question 5

What is cultured butter, and how do butters actually differ?

Accepted Answer

Butter is churned cream, and the differences between butters come down to what happened to the cream first, how much water remains, and what was added afterwards. Sweet cream butter, which is the

Question 6

What is emulsification, and why does mayonnaise split?

Accepted Answer

An emulsion is a stable mixture of two liquids that do not normally mix — oil and water — and it splits when the structure holding them together breaks down. Why oil and water separate. Water

Question 7

How does seasoning a cast iron pan actually work?

Accepted Answer

Through polymerisation — thin layers of oil are heated until they chemically bond into a hard, plastic-like coating on the metal. It is not oil sitting on the surface; it is a new substance formed

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