Молекулярная гастрономия для креативных шеф-поваров (англ. язык) - страница 242

Молекулярная гастрономия для креативных шеф-поваров (англ. язык)

pears with sugar and water in a tin lined pan does not show any reddening, which lead to think that

this culinary precision is wrong. However a study in our laboratory showed that red pear jams can be

obtained not through tin, but through pH adjustment: pears turn red when cooked in acidic

environment, whether tin ions are present or not. It is to be guessed that cooks of the past were able

to see red jams, and mistakenly interpreted that tin was responsible of the effect. In fact, the reddening

is due to some polyphenols molecules naturally present in pears, such as quercitine, who absorb in

the visible spectrum when under a special form called “flavylium”.

Some chemistry of flavour

We are now on the “chemical way”. Let’s stay on it, because it is important in the kitchen, as chemical

processes are responsible of much appreciated flavours.

For example, grilled meat has a very strong flavour due, in particular but not exclusively, to Maillard

processes. These chemical reactions involve sugars such as glucose, and amino acids. The full

description is quite complex, and many odorant molecules are produced, as well as brown products

called melanoidins. It is useful to know that these Maillard processes are not the same with or without

fat, that contribute to the general spectrum of odorant molecules.

As many chemical reactions, Maillard processes occur faster when the temperature increases. More

precisely, any increase by 10°C doubles the speed of the reaction. This explains why people having

diabetes get blind after one life (at 37°C) but why meat turns brown in minutes at 180°C. Contrary to a

wrong idea, this browning occurs at any temperature, and even in boiling water: if glycine and glucose

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are dissolved in water, and the solution is heated, the liquid stays clear for about 30 minutes, and later

only turns yellow, and then brown.

This browning has nothing to do with caramelization, as it is sometimes said by cooks. Caramelization

was a mystery for long, but it was recognized in the last decade that heated sucrose dissociates into a

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