lundi 18 septembre 2017

Dear Friends,
This morning, an question 

If the wine is polar, why do the Chefs use it in order to dissolve the fat (fat is apolar, and insoluble in the polar solvents, but soluble in the apolar solvents) in the method of making a glace ?  And to make  Maillard Reaction ? 

Indeed there are many importants facts to know, in order to understand something to this question.

First, yes, ethanol is soluble in water because both are compounds whose molecules are "polar".
Indeed, in water, molecules are made of two hydrogen atoms and one oxygen atom. As oxygen attracts electrons much, the electron density is higher toward the oxygen, and this makes an electric "dipole". And the same for the OH group of ethanol, so that ethanol, being able to form so called hydrogen bonds with water, cand dissolve into it.

Then, yes, it's true that fat (often triglycerides) does not dissolve in water, but can dissolve is non polar material. Indeed, triglycerides would form only weak bonds (van der Waals) with water molecules, and they would "order" water : this makes the dissolution energetically unfavorable (this does not mean that it is not possible, but only that it does not occur spontaneously in practice ; indeed, if you give energy to such molecules, you can disperse them in water).
By the way, yes triglycerides can be dissolved in apolar solvents such as ethyl acetate, but not in all non polar solvents.

Tomber à glace, making a glace : it means boiling a sauce so that the concentration of solutes increases, and generally in the kitchen, the viscosity increases as well because of gelatine concentration.

Indeed, there is not fat when you make a glace from a stock or a broth. Only the concentration of the solution occurs. And if there is some fat, this fat would form fat droplets dispersed in the solution, i.e. one would get an emulsion, and not a solution.

And the Maillard Reaction ? Indeed, it has no meaning to speak of "the" Maillard reaction, because there are many, so that one should speak of Maillard reactions.
Now, Maillard reactions are chemical reactions between proteins and reducing sugars. I don't see clearly why Maillard reactions would occur when one makes a glace of meat. Indeed, if no sugar present, no Maillard reactions. And indeed, it's time that we stop focusing on this Maillard reactions, and concentrations on the millions other chemical processes that occur during cooking: oxidation, hydrolysis, etc.

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