The Science of Leftovers

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The Science of Leftovers

Tatiana A. Dias
September 22nd, 2017

It’s a well-known fact that some foods improve after sitting for a few hours… But what do they have in common? We look at some of the basic concepts of cooking and what makes some re-heated food taste sooo good!


The chemistry of cooking

When you make a meat sauce or stew, you brown the meat first overheat. The actual chemical reaction that takes place is called the Maillard reaction. The sugar in the protein is reacting with the amino acids in 24 different ways. One of the reactions is polymerisation, another is colour change, and a third is the production of lots of flavour compounds, including caramel. Caramelisation, however, is a completely different chemical reaction despite producing browning and being promoted by heat. Here, sugars combine with other sugars to form larger molecules, the shape and size of which decide the colour and flavour of the final product.




Why do some foods taste better the day after?


Foods that improve with re-heating have a main factor in common; they include a multitude of ingredients with different aromatic properties – such as onion, garlic, peppers, herbs. Aromatic ingredients tend to undergo more reactions that produce flavour and aroma compounds which in turn react with the proteins and the starches.



Refrigeration lets all of the various flavours in the dish to migrate into the cooling protein and starches. When stewed meat cools down, the gelatinous material from the collagen and tendons that has melted during cooking starts to gel. As this happens, the various flavour compounds get trapped in the gel. The same goes for starches. When you cook a starch it gelatinizes. As it cools down, the starch molecules begin to rearrange and realign themselves into a crystalline structure again. As it does this, the flavour compounds from the surrounding sauce are stuck inside the structure.

When you heat a meat dish and then cool it, then reheat it again, the surrounding liquid will thicken because the fibres in the protein break down. This, in turn, releases the interstitial gelatinous material that’s in-between the cells. However, if you continually heat reheat and cool the dish, the meat itself will become gradually stringy as it loses more and more of this gelling material.


So there you have it, delicious leftovers, demystified. What’s your favourite leftover meal?


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“ It's a well-known fact that some foods improve after sitting for a few hours… But what do they have in common? ”

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