Gai Ob Hom Yai

The heat and the aroma of a chilli are made in two different tissues.

Capsaicinoids come from glands on the placenta. The placenta is the pale ridge inside the pod that holds the seeds. No other part of the fruit makes them. The seeds are only hot because they touch the placenta.

The aroma compounds are made in the pericarp. The pericarp is the flesh wall. Capsicum chinense makes esters there that give the apricot and floral smell of a habanero and a reaper.

The two systems do not overlap. So a fat extraction of the placenta gives an oil with almost no smell and very high heat. And flesh with the placenta removed smells like the whole pod at about one fifth of the heat.

This lets you control the two properties separately. Put the flesh in the paste for aroma. Put the placenta in the tincture and add the heat by the millilitre.

Capsaicin is strongly fat-soluble. Its partition coefficient is about 3.6. It is roughly 4000 times more soluble in fat than in water.

In warm oil with nothing to compete, the extraction is almost complete in 15 minutes at 65 degrees C. More heat gives almost no more yield.

More heat does give more vapour pressure. At frying temperature the capsaicin leaves the pan on fat aerosol. This is the same mechanism that riot control sprays use. It will make the kitchen unusable.

Use 80 ml of oil for six pods. Less oil is absorbed by the tissue and the yield falls. More oil only dilutes a fixed quantity of capsaicin.

Onions store carbohydrate as fructans. Heat breaks the fructans into free fructose and glucose. These sugars then react with the amino acids of the onion in the Maillard reaction.

Early in the reaction you get pyrazines and thiols. These taste roasted and savoury. The onion also releases free glutamate.

Later you get melanoidins and maltol. These taste of caramel and fudge. They have low volatility and they stay on the palate.

Those late compounds mask the high-volatility compounds of lemongrass and ginger. Citral, geraniol and the terpenes are lost behind them.

Deep gold gives you the glutamate and the body. It does not give you the mask.

A chicken Maryland is worked muscle. It holds a lot of type I collagen.

Collagen converts to gelatin slowly from 70 degrees C. The conversion is much faster above 80 degrees C. Hold the thigh at 85 to 90 degrees C for a long time. This is far above the temperature you would use for a breast.

The covered stage keeps the air in the tray saturated with water. The meat does not dry while the collagen converts.

But that same saturated air keeps the skin wet. Skin must lose most of its water before it can brown. So the skin cannot crisp under foil at any temperature.

The uncovered stage is a drying stage. It browns the skin because it dries the skin first. The fan matters here. Moving air removes the wet layer of air on the skin surface faster than still air.

Citral is the main aroma compound of lemongrass. It is a pair of molecules, neral and geranial. Citral is very volatile. It leaves with steam.

90 minutes at 145 degrees C removes almost all the citral from anything in the liquid. What stays is the heavier fraction. It is mild and woody. It is useful as a background.

The pounded stalks in the paste give fibre and the compounds held in the cell walls. These release slowly.

The raw shavings at the end are pure top note. They are not heated at all. They are the reason the finished dish smells of lemongrass and does not only taste of it.

The same logic applies to the coriander. The root goes in the paste because its compounds are less volatile and survive the braise. The leaf goes on at the end.

The vinegar and the lime are not interchangeable here.

The Chinkiang vinegar is a cooking acid. It replaces tamarind. It holds the sweetness of the onions and the fat in check across 90 minutes. Acetic acid survives that time. So do the amino acids and melanoidins from the rice ferment, which are not volatile.

Add more vinegar at the end and you add raw acetic acid. It has had no time to combine with the dish. You taste it as a separate sharp note.

Lime is the finishing acid. Citric acid is rounder than acetic acid. The lime also arrives with its aroma intact.

Tamarind leads with tartaric acid, not citric. That is why tamarind tastes round and does not taste sharp. Lime juice cannot do the tamarind job in the pot. Its terpenes boil off in minutes and leave a flat sourness.