How to reheat a ready meal evenly in the microwave

The mash is bubbling at the rim, the sauce has spat onto the glass plate, and the middle of the cutlet is still cold from the fridge. Nothing is wrong with the microwave. This is how microwaves heat, and a handful of habits fixes most of it.

Why the middle lags behind

Microwaves make the water molecules in food vibrate, and that movement produces heat (FDA). Most of the energy lands in the outer layers; the inside of anything thick warms as heat travels inward, and that takes time. The UK Food Standards Agency warns that microwaved food can be very hot at the edges and still cold in the centre, because microwaves heat in pockets (FSA).

Soups and sauces spread heat easily, especially once stirred. Dense food such as mash, thick cutlets or packed rice keeps the heat where it lands, so the surface can bubble over a cool middle. A mixed plate has both problems: the sauce scalds while the chicken beside it is barely warm. Thin edges and corners also heat faster than a thick centre, so Victoria's health department suggests evenly sized pieces, or larger and thicker items towards the outside of the dish (Better Health Channel).

Cutlets with mash, like the plate below, are a typical dense meal: give them the full time on the pack and check the middle, not the edges.

Chicken Cutlets with Mashed Potatoes

510 kcal · P 46 · F 17 · C 43

Per pack. Calculated from the recipe, not measured in a lab.

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Five habits that even the heat out

1. Start with the pack. Its instructions are written for that dish and portion, and the FSA advises following the original packaging where instructions are given.
2. Let the steam out. Health Canada recommends a microwave-safe lid or wrap that doesn't touch the food, with a small gap for steam (Health Canada). "Pierce the film" on a pack asks for the same thing.
3. Stir or turn the food if the pack and container allow it. Health Canada advises doing it several times, and the FSA notes that it helps with cold pockets. Mind the steam.
4. Keep the standing time. It completes the cooking and spreads the heat (Health Canada); Victoria's advice is to check the food only once it is over.
5. Use a container made for the microwave. In your own dish, Thailand's FDA advises one marked "Microwave Safe" or "Microwavable", no unmarked containers and no reused single-use plastic (Thai FDA). Keep metal out: the US FDA notes it reflects microwaves and makes food cook unevenly.

Steaming hot, all the way through

The FSA's standard is food that is steaming hot throughout, not just warm. Victoria's health department puts it above 75 °C or preferably boiling, Health Canada at 74 °C for leftovers. These are recommendations from other countries, not Thai law, but the reasoning is universal: heat kills bacteria that may be present.

Without a food thermometer, use the FSA's visual check: steam should rise from the surface and from the middle when you cut into it. If the centre is lukewarm, heat a little longer and check again.

The FSA also advises reheating food only once, because each round of cooling and warming gives bacteria another chance to grow. Heat only what you will eat now, eat it soon, and don't put a reheated meal back in the fridge for later.

At the machine or at home, the pack decides

Meals in our machines are chilled, not frozen, so you heat them from fridge-cold with no thawing (chilled vs frozen meals). Every meal has a use-by date on the pack, and packs carry reheating instructions written for the meal in your hand. Follow them rather than a rule of thumb.

To eat straight away, use the machine: it has a built-in microwave that heats a meal after purchase and only works after a purchase, so it doesn't turn into a shared microwave. The steps are in the first purchase guide. A meal taken home stays in the fridge until you heat it, and if your microwave's power differs from the one on the pack, the time changes too; how to read and adjust reheating instructions has the method.