Posts Tagged ‘sodium alginate’

Help needed with densities of hydrocolloids

Wednesday, April 30th, 2008


Photo by Mel B via flickr.com (CC).

Measuring powders by volume has serious limitations (more on this later in an up-coming post), but one great advantage is that for small quantities going by volume can sometimes be more accurate than weighing them. At least when you work in a kitchen and don’t have access to professional lab scales. When a scale shows 0.1 g, the true weight could be anywere from 0.05-0.149 g due to rounding (that’s ± 50%!). Not to mention the fact that cheap balances aren’t always very accurate for such small amounts, even though they feature a 0.1 g resolution.

I’m currently working on a major revision of the collection of hydrocolloid recipes. One thing I would like to include is a table with densities of the hydrocolloids and chemicals used. When the densities are known, it’s possible to give some rough advice for what volume to use (this on-line conversion calculator has the densities of many common ingredients). This could ease small scale preparations. It will also make it easier to calculate the percentage of hydrocolloid used in recipes where the amount is given by volume. I’ve measured the hydrocolloids I have at hand, but I need your help to fill out the table and repeat the measurements I’ve done. With enough measurements I could also do some statistics and make a plot. I’m also interested to see if there is much variation between different brands.

How to determine the density:

  1. Find a suitable measuring spoon, cup, shot glass, container – whatever you have – with a volume of at least 10 mL (I used one of about 30 mL).
  2. Put the empty container on the balance and use the tara function.
  3. Fill completely with water and weigh again. The difference gives you the exact volume (for water 1 g = 1 mL).
  4. Dry the container, put it on the balance and use the tara function.
  5. Spoon the hydrocolloid into the container, tap the side gently once or twice with the spoon and level off.
  6. Weigh the container again and write down the mass of the hydrocolloid.
  7. To calculate the density of the hydrocolloid, divide the mass by the volume you obtained for your container. This gives you the density of the hydrocolloid with units g/mL.

Repeat steps 4-7 for each hydrocolloid you have at hand. I would very much appreciate if you email your results directly to me at webmaster (@) khymos (.) org. Please include the volume you measured (larger volume means more accurate measurement) and which brand you used. It will be interesting to see if the brands differ a lot.

I should add one coment about the products from texturePro: this picture indicates that all (?!!) the texturePro hydrocolloids are mixed with maltodextrin (please correct me if I’m wrong – it could be that this only applies to the cocktailPro kit). And I think the same is the case for several of the Sosa products. This increases the volume and eases the use of a measuring spoon (which comes with every texturePro kit), but unless the exact proportion of hydrocolloid to maltodextrin is known, following other recipes than the onces included with the kit is more or less impossible. Let me know if you have further details on the hydrocolloid/maltodextrin ratio in texturePro or Sosa products.

In advance: Thank you very much for your help!

Hydrocolloid recipe collection

Tuesday, August 14th, 2007

I’m happy to finally announce the first edition of a recipe collection devoted mainly to hydrocolloids. Totaling 111 recipes, it’s available for download as a pdf file (29 pages, 433 kB).

Update: The collection has been revised and is now available for download (more than 220 recipe, 73 pages, 1.8 Mb).

The following text is from the introduction I’ve written to the recipe collection:

A hydrocolloid can simply be defined as a substance that forms a gel in contact with water. Such substances include both polysaccharides and proteins which are capable of one or more of the following: thickening and gelling aqueous solutions, stabilizing foams, emulsions and dispersions and preventing crystallization of saturated water or sugar solutions.

In the recent years there has been a tremendous interest in molecular gastronomy. Part of this interest has been directed towards the “new” hydrocolloids. The term “new” includes hydrocolloids such as xanthan which is a result of relatively recent research, but also hydrocolloids such as agar which has been unknown in western cooking, but used in Asia for decades. One fortunate consequence of the increased interest in molecular gastronomy and hydrocolloids is that hydrocolloids that were previously only available to the food industry have become available in small quantities at a reasonable price. A less fortunate consequence however is that many have come to regard molecular gastronomy as synonymous with the use of hydrocolloids to prepare foams and spheres. I should therefore emphasize that molecular gastronomy is not limited to the use of hydrocolloids and that it is not the intention of this collection of recipes to define molecular gastronomy.

One major challenge (at least for an amateur cook) is to find recipes and directions to utilize the “new” hydrocolloids. When purchasing hydrocolloids, typically only a few recipes are included. Personally I like to browse several recipes to get an idea of the different possibilities when cooking. Therefore I have collected more than 100 recipes which utilize hydrocolloids ranging from agar to xanthan. In addition to these some recipes with lecithin (not technically a hydrocolloid) have been included. Recipes for espumas that do not call for addition of gelatin or other thickening agents have also been included for completeness.
All recipes have been changed to SI units which are the ones preferred by the scientific community (and hopefully soon by the cooks as well). As far as possible, brand names have been replaced by generic names. Most of the recipes have been edited and some have been shortened significantly. In some recipes, obvious mistakes have been corrected. But unfortunately, the recipes have not been tested, so there is no guarantee that they actually work as intended and that the directions are complete, accurate and correct. The recipes have been collected from various printed and electronic sources and every attempt has been made to give the source of the recipes.

Since recipes can neither be patented nor copyrighted, every reader should feel free to download, print, use, modify, distribute and further develop the recipes contained in this compilation. The latest version will be available for download from http://khymos.org/recipe-collection.php and will also be announced at http://blog.khymos.org. Feedback, comments, corrections and new recipes are welcome at recipe.at.khymos.dot.org.

Martin Lersch
Oslo, August 2007

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.; Skjåk-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.; Skjåk-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.