molecular gastronomy :: boric acid caramel

This is a guest blog post by Laurence Humier and includes a recipe from her new book (written in collaboration with Audrey Tardieu) Cooking Material: Could molecular gastronomy help discover new matter? (also available on Amazon).

The preparation for boric acid caramel is similar to sugar caramel. Both are glass soluble in the water. One is edible, the other not.

:: ½ cup of boric acid powder
:: 3 teaspoons of water
:: ¼ cup of silicone oil
:: optional colored mineral pigment

Boric acid (H3BO3) is a weak acid, used for medical applications (antiseptic and antibacterial) and also as a neutron absorber in the nuclear industry. Do not inhale or allow its vapors to reach your eyes when heated. It is sold in drugstores.

Combine together the ingredients and bake in the oven at 480°F. After one hour, the boric acid will be dissolved and the liquid viscous and transparent. Cool for 90 minutes by slowly turning the oven temperature down, to avoid thermic shock (when hot material hits cold air, it often cracks). While cooling, the mass becomes solid. Sugar caramel results mainly from a series of chemical reactions (caramelizing reactions), boric acid caramel develops from a physical transformation (fusion). Both materials look alike on a macroscopic level. They are both brittle and water soluble.

Out of the oven, the glass cools and hardens in a few seconds. There is no time for pouring it into a mold. Adding silicone oil instead of water, before baking, allows the caramel to get more viscous and malleable. Adding water is useless, because it evaporates as soon as the temperature reaches 212°F.

The recipes to obtain the materials inside the e-book are easy but it’s important to note the main concept: the tie between culinary ingredients and non-culinary materials. An ingredient is a material! Do you know that we temper chocolate in the same way we quench titanium/nickel alloy to obtain shape-memory metal? The rank of temperature is of course different. In the case of chocolate, I get new properties (crunchiness and shiny exterior) but the process is the same: quickly cool a material (or an ingredient) previously heated to permit an atomic reorganization of the material (or the ingredient).

I believe that cooking is not only about nourishing our body but about material change of states (from water you get ice cream or a crystallize material!) and about control of shelf life of material (you make jam to conserve fruit as cheese to conserve milk!).

Material change of states and control of shelf life of materials are two important topics in material sciences.

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