On m'interroge à propos de croustillant : comment en
obtenir quand on cuisine ?
About crackling, how to get it ? (in English at the bottom of the page.
Pour une telle question, il y a lieu
d'analyser un peu en n'oubliant pas ces "commandements" que j'avais donné s
dans mon livre Mon histoire de cuisine.
Je ne vais pas les rappeler
tous, car il y en a 14, et certains n'ont pas de rapport avec la question
qui nous intéresse. En revanche, je propose d'observer que les liquides
sont... liquides, et que les solides sont... solides.
Cela suffit en réalité à
tout dire à condition de savoir que nos aliments sont souvent des assemblage de composés qui sont soit solides soit liquides dans les conditions
ambiantes.
Par exemple la farine est solide, mais l'eau est liquide, et
l'huile aussi. Dans une pâte, par exemple il peut y avoir des grains de
farine - solides- dispersées dans un liquide, et cette "suspension" peut-être
plus ou moins molle, plus ou moins dure.
Mais restons à cette
expérience de disperser de la farine dans de l'eau. On obtient une pâte
plus ou moins molle, selon la proportion de solide : par exemple, avec beaucoup d'eau et peu de farine, on a une poudre dispersée (qui finit par sédimenter). Mais avec beaucoup de farine et peu d'eau, on a une pâte plus dure.
A la cuisson, cette pâte peut durcir. Si on la sèche, c'est-à-dire si l'on
élimine liquide, alors on obtient quelque chose de très dur, qui
peut-être est craquant si on a une couche un peu épaisse, et croustillant
si l'on a milles petits "crac" qui résultent de la rupture de nombreux
feuillets, comme dans une pâte feuilletée.
Cette analyse, faite pour l'eau, ne vaut pas pour l'huile, qui ne s'évapore pas à la cuisson : si l'on répète la même expérience que précédemment mais en remplaçant l'eau
par du beurre, qui fondra quand il chauffera, on récupérera une pâte
sablée, avec des grains de farine dispersées dans du beurre qui, au
refroidissement, vont durcir un peu.
Et s'impose
maintenant une discussion relative à l'énergie de liaison des molécules
dans les solides.
Dans un cristal de sel, les liaisons entre les atomes
de sodium et de chlore sont très forts (ce sont des liaisons "électrostatiques", de sorte que de tels cristaux sont très
résistants, très durs.
Idem pour des cristaux de sucre, où, les molécules de saccharose sont tenues par de nombreuses "liaisons hydrogène".
Idem dans les grain d'amidon,, puisque les "polysaccharides" (amylose et amylopectine) qui composent ces grains sont des polymères de saccharides, toujours avec les liaisons hydrogène précédemment considérées pour le sucre de table, ou saccharose.
Pour les matières grasses, telle l'huile que l'on fait figer, les cristaux formés sont bien plus mous, parce que les liaisons sont des "liaisons de van der Waals", environ dix fois plus faibles que les liaisons hydrogène, et plus de cent fois plus faibles que les liaisons électrostatiques (je donne des ordres de grandeur).
Bref, on n'oubliera donc pas de penser à la chimie, si l'on
veut maîtriser parfaitement le croustillant, notamment pour ceux qui se
préparent à participer au 8e concours de cuisine note à note.
PS. Pour les plus chimistes, voici une image que je crois de salut public de distribuer
The translation in English :
I'm asked about crispness: how do you get it when you cook?
For such a question, it is necessary to analyze a little while not forgetting these "commandments" that I had given in my book Mon histoire de cuisine.
I am not going to recall them all, because there are 14 of them, and some of them are not related to the question we are interested in. On the other hand, I propose to observe that liquids are... liquids, and solids are... solids.
That's really enough to say it all if you know that our food is often a collection of compounds that are either solid or liquid under the ambient conditions.
For example, flour is solid, but water is liquid, and so is oil. In a dough, for example, there may be grains of flour - solids - dispersed in a liquid, and this "suspension" may be more or less soft, more or less hard.
But let's stick to this experiment of dispersing flour in water. We obtain a more or less soft paste, depending on the proportion of solid: for example, with a lot of water and little flour, we have a dispersed powder (which ends up sedimenting). But with a lot of flour and little water you get a harder dough.
When baking, this dough can harden. If you dry it, i.e. if you remove the liquid, then you get something very hard, which may be crunchy if you have a thick layer, and crispy if you have a thousand little "cracks" resulting from the breaking of many layers, as in a puff pastry.
This analysis, made for water, does not apply to oil, which does not evaporate during cooking: if we repeat the same experiment as before, but replacing the water with butter, which will melt when it heats up, we will recover a shortbread dough, with grains of flour dispersed in butter which, on cooling, will harden a little.
And now a discussion about the binding energy of the molecules in the solids is necessary.
In a salt crystal, the bonds between the sodium and chlorine atoms are very strong (these are "electrostatic" bonds, so that such crystals are very resistant, very hard.
Same for sugar crystals, where the sucrose molecules are held by many "hydrogen bonds".
Ditto in starch grains, since the "polysaccharides" (amylose and amylopectin) that make up these grains are polymers of saccharides, again with the hydrogen bonds previously considered for table sugar, or sucrose.
For fats, such as oil, which is frozen, the crystals formed are much softer, because the bonds are "van der Waals bonds", about ten times weaker than hydrogen bonds, and more than one hundred times weaker than electrostatic bonds (I give orders of magnitude).
In short, one should not forget to think about chemistry, if one wants to perfectly master the crispness, especially for those who are preparing to participate in the 8th note-to-notes cooking contest.
PS. For the most chemists, here is a picture that I think of public salvation to distribute
For such a question, it is necessary to analyze a little while not forgetting these "commandments" that I had given in my book Mon histoire de cuisine.
I am not going to recall them all, because there are 14 of them, and some of them are not related to the question we are interested in. On the other hand, I propose to observe that liquids are... liquids, and solids are... solids.
That's really enough to say it all if you know that our food is often a collection of compounds that are either solid or liquid under the ambient conditions.
For example, flour is solid, but water is liquid, and so is oil. In a dough, for example, there may be grains of flour - solids - dispersed in a liquid, and this "suspension" may be more or less soft, more or less hard.
But let's stick to this experiment of dispersing flour in water. We obtain a more or less soft paste, depending on the proportion of solid: for example, with a lot of water and little flour, we have a dispersed powder (which ends up sedimenting). But with a lot of flour and little water you get a harder dough.
When baking, this dough can harden. If you dry it, i.e. if you remove the liquid, then you get something very hard, which may be crunchy if you have a thick layer, and crispy if you have a thousand little "cracks" resulting from the breaking of many layers, as in a puff pastry.
This analysis, made for water, does not apply to oil, which does not evaporate during cooking: if we repeat the same experiment as before, but replacing the water with butter, which will melt when it heats up, we will recover a shortbread dough, with grains of flour dispersed in butter which, on cooling, will harden a little.
And now a discussion about the binding energy of the molecules in the solids is necessary.
In a salt crystal, the bonds between the sodium and chlorine atoms are very strong (these are "electrostatic" bonds, so that such crystals are very resistant, very hard.
Same for sugar crystals, where the sucrose molecules are held by many "hydrogen bonds".
Ditto in starch grains, since the "polysaccharides" (amylose and amylopectin) that make up these grains are polymers of saccharides, again with the hydrogen bonds previously considered for table sugar, or sucrose.
For fats, such as oil, which is frozen, the crystals formed are much softer, because the bonds are "van der Waals bonds", about ten times weaker than hydrogen bonds, and more than one hundred times weaker than electrostatic bonds (I give orders of magnitude).
In short, one should not forget to think about chemistry, if one wants to perfectly master the crispness, especially for those who are preparing to participate in the 8th note-to-notes cooking contest.
PS. For the most chemists, here is a picture that I think of public salvation to distribute
