Posts Tagged ‘sphere’

First experiments with sodium alginate

Friday, March 30th, 2007

Here’s some pictures and a video of my first experiments with sodium alginate and spherification. I used sodium alginate from the Texturas series and calcium chloride from a drug store. Needless to say, I’m very fascinated by the texture and the whole process. I have blogged about the chemistry behind previously.

Materials used:
2.0 g sodium alginate
200 g water (with low calcium content!)
50 g blueberry syrup

2.5 g calcium chloride
500 g water

Procedure:
2 g sodium alginate and 200 g water were mixed vigourously in blender. The mixture was then left to stand for some hours to get rid of the air bubbles. 50 g blueberry syrup was then added to the sodium alginate solution. A calcium chloride bath was prepared by dissolving 2.5 g calcium chloride in 500 g water. The sodium alginate/blueberry mixture was dripped into the calcium chloride bath using a plastic syringe with a steel cannula. After 1-3 min the pearls were removed and rinsed with water.

More detailed procedure with pictures and video:
I had to obtain a scale with a 0.1 g accuracy to weigh out 2.0 g of sodium alginate (my first experiments using a normal kitchen scale failed). The model I got cost about $100 and is inteded for school laboratories. Amazon provides several scales with this accuracy.

alginate-1.jpg

I used a blender to dissolve sodium alginate in water. This incorporates a lot of air in the mixture which we don’t want. It could possibly be avoided by using an immersion blender/mixer. However, I just left the alginate solution on the bench and after 3-4 hours the air bubbles had all escaped from the solution.

alginate-2.jpg

Plastic syringes and cannulas can be obtained from your local drug store or pharmacist. I found it was easier to produce evenly sized drops with a sharp cannula (CAREFULL!) than with just the plastic tip of the syringe. This of course depends on the viscosity of the solution. By thickening (with xanthan for instance) you can produce larger drops.

alginate-6.jpg

After 1-3 min the spheres were removed from the calcium chloride solution and rinsed with clean water. I dried the spheres carefully using a kitchen towel or paper.

alginate-7.jpg

alginate-3.jpg

Definitely looks like caviar when presented on a spoon like this!

alginate-4.jpg

Larger spheres were made by filling a small measuring spoon with the alginate mixture (I used a syringe for this so the outsides of the spoon would not be covered with alginate solution) and carefully emptied it into the calcium chloride bath. It takes some trial and error to achieve good results.

alginate-5.jpg

The spheres are suprisingly robust and can be handled without rupturing.

alginate-8.jpg

If cut with a knife, the spheres rupture and the liquid contents flows out.

alginate-9.jpg

The small spheres didn’t taste much, so I could have added more blueberry syrup. The large spheres however had a nice taste. The surprise element when they rupture in your mouth is very nice!

Video on alginates

Sunday, September 17th, 2006

My fellow blogger on molecular gastronomy, Göde Schüler (check out his German MG blog Gourmetrics) found a great video on YouTube. The video shows how a red beet paste mixed with alginate solidifies when dripped into a solution of calcium lactate (this solution is normally clear, the yellow colour comes from extensive use).

Chef Simon (French, click here for babelfish translation) has a nice page on alginates as well. Another french page here (with english translation by babelfish). You can find links to more technical information (free pdf’s) on alginates in the static pages of khymos.org.

The chemical principles put simply are as follows:
Sodium alginate is water soluble and can be mixed with many different fruit/vegetable juices and purés. When dripped into a solution containing calcium ions, each calcium ion (which holds a charge of +2) knocks away two sodium ions (each holding a charge of +1). The alginate molecule contains loads of hydroxyl groups (OH’s) that can be coordinated to cations (that’s ions with a positive charge such as sodium and calcium).

calcium alginate
Figure from Draget, K. I.; Smidsrød, O.; SkjÃ¥k-Bræk, G. “Alginates from Algae” in “Polysaccharides and Polyamides in the Food Industry. Properties, Production, and Patents”, Steinbüchel and Rhee (Ed.), Wiley 2005.

When alginate is coordinated to sodium, it’s a very flexible chain. When sodium is replaced by calcium however, each calcium ion (black dots in the image below) coordinates to two alginate chains, linking them together. The flexible chains become less flexible and form a huge network – a gel. The fun thing is that this happens within seconds after the alginate mixture is dripped into the water bath with the calcium ions.

Two alginate chains
Figure from Draget, K. I.; Smidsrød, O.; SkjÃ¥k-Bræk, G. “Alginates from Algae” in “Polysaccharides and Polyamides in the Food Industry. Properties, Production, and Patents”, Steinbüchel and Rhee (Ed.), Wiley 2005.

Approximate concentrations:

  • Fruit/vegetalbe juice/puré with 1-2% sodium alginte
  • 2% calcium chloride solution (approx. 10g in 1/2 L of water) – because calcium chloride has a slightly bitter taste, it is a good idea to rince these pearls with water before consumption. This is also the reason why calcium lactate is often used in stead (as shown in the video).

Update: The Frog Blog has nice posts with pictures showing how Jay Veregge and Joel Robuchon utilize alginate gels. Also, check out this “caviar” maker for dripping 96 drops of sodium alginate solutions into calcium chloride at once.