Diallyl disulfide
Also written diallyl disulphide, DADS
Quick answer
The garlic smell that remains once allicin has broken down — the aroma of cooked garlic, garlic oil and garlic breath rather than the sharp bite of garlic freshly crushed.
What it does
Allicin, formed when garlic is crushed, is unstable and does not last: within hours at room temperature, and far faster when heated, it decomposes into a family of sulfides, of which diallyl disulfide is the most important. The sulfides smell of garlic but not of raw garlic — rounder, heavier, less pungent — and they are what cooked garlic, garlic oil and most garlic products carry. The shift from the bite of raw garlic to the savoury depth of cooked garlic is largely this conversion.
How it behaves when cooked
Four properties of the molecule, and what they mean at the stove.
- Volatility
- high
- Fat solubility
- high
- Water solubility
- low
- Heat stability
- moderate
Oil-soluble and volatile, which is why garlic flavours oil so thoroughly and why that flavour carries across a room. Because it forms from allicin, the amount of it depends on whether allicin was made first: garlic crushed and then cooked produces the sulfides in quantity; garlic roasted whole before it is cut never made much allicin, because heat destroyed the enzyme first, and ends up mild and sweet instead. Frying chopped garlic in oil moves quickly from allicin’s sharpness through the sulfides to bitterness once the garlic browns, which is why garlic goes into a pan after the onions rather than before them.
Not present until the plant is damaged
Allicin (itself formed from alliin when the clove is crushed)
The second stage of a two-stage chain. Crushing lets the enzyme alliinase turn odourless alliin into allicin; allicin then decomposes into diallyl disulfide and related sulfides, spontaneously over hours and quickly with heat.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
What cooking and processing were measured to do to it
Findings from studies in which this compound was followed through heat, fat, water, drying or storage. Each belongs to its study and its conditions.
Frying and blooming in fat · Decreases Diallyl disulfide, Monoterpenes, Methylpyrrole, Aldehydes from the heated oil, volatile oil
Garlic, Ginger, Sichuan pepper
What is smelled when spices hit hot oil is aroma leaving the pan. Stir-frying garlic released abundant diallyl disulfide into the air; stir-frying ginger and Sichuan pepper released abundant monoterpenes and related terpenoids; all of the spices tested gave off methylpyrrole, and the aldehydes emitted by the heated oil itself rose roughly tenfold once spices were added. A separate study of a test kitchen, in which 16 herbs and spices were shallow-fried in rapeseed oil and a chicken curry was cooked, found the same pattern by stage: aldehydes while the oil heated, monoterpenes while the spices fried.
Conditions: in oil or fat · Spices stir-fried in corn oil; emissions measured in the air by on-line mass spectrometry
Frying a spice in fat is not only an extraction into the oil. Part of the lightest aroma is driven off into the room in the same moment, which is one reason the time a spice spends in hot fat is kept short.
What this does not show: Both read in the abstract only, and both are air-quality studies: they measured what entered the air and not what stayed in the oil or the food, so the share lost cannot be stated. The first study names its Sichuan pepper as Zanthoxylum piperitum.
Measured on the spice
Not to be confused with
Compounds a reader is likely to take for this one, and why they differ.
Allicin
Its precursor, and the pungency of freshly crushed raw garlic. The difference between the two is the difference between raw and cooked garlic.
Questions this page answers
- why does cooked garlic taste different from raw
- what is diallyl disulfide
- allicin breakdown cooking