mussel shells

pearls: direct vs reverse spherification

direct spherification

INGREDIENTS:

PROCESS:

  1. prepare the alginate solution
  2. mix and mold
  3. cross-linking in calcium chloride bath
  4. drying and sanding

PREPARE THE ALGINATE SOLUTION

1.

  • Pour water into a tall container with a lid and add the alginate;
  • Mix well with a whisk. It can help you closing the lid and shaking the container for a couple of minutes;
  • Leave the solution in the fridge overnight to make it homogeneous and to let out the air bubbles.

MIX AND MOLD

2.

  • Weight the shells powder and the alginate solution;

With 3 parts of grinded shells (e.g. 30gr) and 1 part of alginate solution (e.g. 10gr) you get a compound you can mold with your hands.

  • Mix well with a spoon to make the mixture as homogeneous as possible;
  • Shape the mixture with your hands into small spheres.

CROSS-LINKING IN CALCIUM CHLORIDE BATH

3.

  • Prepare a 1% calcium chloride solution with water (e.g. 6grcalcium salt in 600mlwater); 
  • Dip the shells composite in the calcium chloride bath for 10-20min;
  • Let it air dry. It is now water resistant (but will absorb water if soaked).

DRYING AND SANDING

4.

  • Let the pearls air drying;
  • Sand them with fine sand paper to reveal the varied texture of the shell fragments.

reverse spherification

INGREDIENTS:

  • 20gr grinded musselshells – nacre layer (recipe to get the nacre here)
  • 0,3gr calcium chloride in 12ml water
  • 8gr sodium alginate in 800ml water -1% (m/v) alginate solution-

PROCESS:

  1. prepare the alginate solution
  2. mix the ingredients
  3. cross-linking in alginate bath
  4. drying

PREPARE THE ALGINATE SOLUTION

1.

  • Pour water into a large container with a lid and add the alginate;
  • Mix well with a whisk. It can help you closing the lid and shaking the container for a couple of minutes;
  • Leave the solution in the fridge overnight to make it homogeneous and to let out the air bubbles.

MIX the ingredients

2.

  • Using a mortar, grind 20gr of nacre;
  • Using the back of a spoon grind 0.3gr of calcium chloride and mix it with 12ml of water;
  • Add the nacre powder to the mixture.

CROSS-LINKING IN alginate BATH

3.

  • Gradually drop the mixture in the alginate bath with a teaspoon in the shape of pearls, gently moving the alginate solution from time to time;

Be careful to keep the drops distant from each other (otherwise they will stick together). A transparent film is formed all around the drop.

    • Let the pearls dipped in the bath for 5-10 minutes.

DRYING

4.

  • Rinse the pearls with the help of a strainer;
  • Let them air dry.

HOW DOES THIS HAPPEN?

alginic acid

Alginic acid is an hydrophilic substance that comes from seaweeds. Its derivatives are called alginates and are commonly used (sodium alginate in particular) as thickeners in food, in pharmaceutical and in cosmetic industry between others.

Alginate is a long, negatively charged, noodle-like molecule. When mixed into a liquid, alginate floats about freely, its elongated structure creating a thick, jelly-like consistency.

cross-linking

Adding a calcium salt to sodium alginate in aqueous medium, calcium alginate is formed, a water-insoluble gelatinous substance. In this process, called cross-linking, positively charged calcium ions link together with alginate molecules. Many calcium-linked alginate molecules form a more solid structure compared to non-crosslinked sodium alginate.

spherification

Spherification is a technique that belongs to molecular gastronomy. It consists in shaping a liquid into squishy spheres, using the ability of sodium alginate to instantly jellify when in contact with calcium salts, like calcium chloride or calcium lactate. This is the same technique used to make the Ooho balls, an alternative way of packaging water.

DIRECT vs REVERSE SPHERIFICATION
In fact there are two different methods to creating such spheres: direct and reverse spherification. For reverse spherification alginate gelling agent is added to the setting bath, while in direct spherification you put it in the base.