Marinating: how long actually makes a difference

Marinating overnight has become a sort of received wisdom: longer is better, and if the chicken was only in there two hours you have somehow cut a corner. For most things you cook at home, that is not true, and for a few it actively makes the food worse.

What a marinade actually does

Three things, and only one of them is what most people assume.

It seasons the surface. This is the main event. Flavour compounds from garlic, spices, soy and sugar sit on and just under the surface, and that is where they stay.

It helps things brown. Sugars and proteins in a marinade give you colour and char that plain meat would not produce.

It changes texture, at the surface. Salt, acid and enzymes all alter the outer few millimetres of protein, which affects how the food feels to eat.

What it does not do is carry flavour deep into a piece of meat. That is the persistent myth, and once you let go of it the timings make more sense.

Only salt travels

Of everything in a typical marinade, salt is the one ingredient that genuinely moves through muscle. Large flavour molecules from garlic, lemongrass and spices are simply too big to migrate more than a millimetre or two, however long you leave them.

This is why a marinated chicken thigh tastes strongly seasoned on the outside and plain in the middle, and why extending eight hours to twenty-four changes very little except the surface.

It also explains why salting a piece of meat well in advance does more for it than a complicated marinade applied late. If you only have thirty minutes, salt it properly and skip the rest.

Acid is on a timer

Lime, tamarind, vinegar and yoghurt all denature protein at the surface, which starts as tenderising and ends as damage.

Leave fish in a sharp acidic marinade for an hour and the outside turns opaque and firm; that is ceviche, and it is a technique rather than an accident. Leave chicken in one overnight and the surface goes chalky and slightly mealy after cooking.

The stronger the acid, the shorter the window. This is the single most common way an overnight marinade makes food worse rather than better.

Yoghurt and santan are the exception

Dairy and coconut marinades behave differently from sharp acidic ones. They are mildly acidic, they cling well, and their fat carries fat-soluble spice compounds that a watery marinade leaves behind.

They also tenderise gently rather than aggressively, which is why tandoori-style and many Malaysian grilled preparations use them and genuinely benefit from a long soak. If you want to marinate something overnight, this is the kind of marinade to do it with.

The sugar problem

Kicap manis, gula Melaka and honey all make excellent marinades and all burn well before the inside of the meat is cooked.

There are two ways round it. Cook over moderate heat and accept a longer cook, or marinate without the sugar and brush the sweet element on during the last few minutes. Satay and grilled chicken both work this way: the sweet glaze goes on at the end, repeatedly, rather than sitting in the marinade from the start.

If your grilled chicken is consistently black outside and underdone inside, sugar is why.

Dry it before it hits the heat

A wet surface has to boil dry before it can brown, and while that happens the food steams. Meat straight from a marinade into a pan will be grey before it is golden.

Lift it out, let it drain, pat it with paper. You lose almost none of the flavour, since the seasoning is already in the surface, and you gain the browning that makes the dish look and taste cooked rather than simmered.

The leftover marinade

It has been sitting in contact with raw meat, so it is not a sauce. Either discard it, or bring it to a proper boil for several minutes first, at which point it is safe and often very good.

Boiling also thickens it slightly and concentrates the flavour, which makes it a better glaze than it was a marinade. If you want a sauce to serve alongside, reserve some before the meat goes in and keep it separate.