Reference point
Render a little pork fat until the cracklings turn golden, and smell them as soon as they come out.
Do this before you read on. An entry only works when you have just smelled the thing.
Fatty, sweet, with a grilled-meat note and a light scorch. Dense and far-reaching.
Raw fat has almost no smell. Everything here is created by heat acting on the fat and the little protein left in it — a process different from the sugar–amino acid reaction in scorched rice, producing quite different compounds.
This entry stands for a whole family of kitchen smells that still has no name in the vocabulary: the smell of fat and meat meeting fire.
How to smell it
Render a little diced pork fat until the cracklings turn golden. Smell at three moments: when the fat first melts, when the cracklings turn golden, and when they begin to brown. Three different smells in the same pan.
Why this one is hard
Because it is tied to hunger more strongly than almost any other smell in the dictionary, and the physiological reflex overrides analysis.
Scientific note
Pork crackling carries lactones and aldehydes produced when animal fat is oxidised under heat. The same lactones are found in toasted coconut and condensed milk. Three very different sources give a similar fatty impression, because the brain reads that group of compounds as a texture rather than as an origin.
In Vietnamese life
Pork crackling was once a food of hard times and has now come back as a snack. For many people born before the 1990s the smell of rendering lard is the smell of the family kitchen before industrial cooking oil became common.