January | 2011 | Molecular Gastronomy Blog

Molecular gastronomy – oil and viscosity

January 21, 2011 moleculargastronomy 6 comments

Hello everyone,

It’s been awhile since I’ve posted material here on molecular gastronomy. I’m happy to announce that my absence was based on my recent trip to visit Molecular Chefs Jose Andres and Masterchef Ferran Adria!!!

I learned way too much and can’t wait to share with you ALL!

Another great piece of news I’ve got is my new molecular kitchen device.

Here is my new Toy: The Thermomix

Now to bore you with the MAD food science I learned while away. FYI, there are some great recipes past the science if you want to just scroll down. Enjoy!

Oil and viscosity

Molecular viscosity : v = l x c

elasticity: E = kBT/l³

When talking about the elasticity you got to imagine a spring. Imagine how the spring stretches and you will obverse its elastic constant. What makes foods soft, squishy or flow easily is critical to all aspects cooking. It is for this reason that we must examine the properties of elasticity and viscosity when dealing with food.

Here is an example of the elasticity of a raw thaw steak:

Elastic constant of a steak

E = F ⁄ A L ⁄ ΔL

E= 8,000 Pa

The amazing formula is as follows:

E =kT ⁄ l³

Elasticity / / (volume)

Before Cooking (RAW) 8×10³ Before 8.1 nm Before 8.1 nm

After Cooking (Cooked) 5×10⁴ After 4.4 nm After 6.8 nm

The stiffness of a material depends on the length between bonds .

Energy of bonds times their density

Stretching bonds to deform the solid

Units – Energy density

Viscosity

A material is a liquid if the molecules can move around each other

The fundamental quantity that governs this is the time that it takes for molecules to move around their neighbors.

If it takes a long time to move by each other, the material is very viscous.

If it takes a short time, the material is less viscous.

Example: Olive Oil

It takes longer for the molecules to move through olive oil than water because it has a higher viscosity.

Molecular viscosity

length²/time v = l x c

where v = length

c = length ⁄ time

Very important Equations:

Molecular viscosity: v = l x c

elasticity: E = kBT ⁄ l³

Let’s look at the viscosity of hot oil

Hot oil flows faster than cold oil

Viscosity decreases with increasing temperature

Molecules move around each other more easily

Let’s look at how using a thickener helps make liquids thicker

Xanthan Gum makes liquids thicker

Xanthan Gum (E415): makes food thick and creamy; also stabilizes foods to help solids and liquids stay together

You could see Xanthan Gum is sauces, low fat or non-dairy, and dressings.

The reason thickeners works?

Thickener is a polymer

Polymer forms network in the water

This forms a solid gel

Note: The bonds in gels are not permanent

Molecules can move

Molecules must disentangle to move

This is important because it means if you form a gel you could easily manipulate it by shredding it in a thermomix or blender.

doing this will change the viscosity by either a small percentage or a large one.

Let’s get into some recipes with some molecular ingredients:

Soft Creamy Jelly

You will need:

100g of water, fruit juice, or wine.

2.5g iota

100g of olive oil (extra virgin)

Procedure:

You will need to bring water to boil and stir in iota, whisking constantly. Take the saucepan out of the warmer and slowly add the olive oil, stirring constantly.

Pour mixture into molds and allow to cool.