Agar or Alginate Spherification – what’s the difference?
Spherification is a BIG topic to cover. It seems so simple when you see them used on desserts, Hors D’oeuvres, and even in drinks. In a sense spheres are simple as they are just small pockets of flavor that you add to a dish for an exciting pop of flavor. But the method is one that has many little intricacies that can be frustrating. For instance acidity can ruin your day when you first get into spherification. So a the first lesson is measure the pH of your flavorful liquid. This can easily be done with litmus test strips or a pH meter. You want the ph to be above 4pH, if the liquid is not above a 4 on the pH scale traditional spherification will not work. You will have to buffer the acidity by using sodium citrate. If you do not buffer the acidity the spheres will not form.
There are a few different types of spherification that you can make. The most common being direct, reverse, and frozen reverse spherification. These are all made using two ingredients, sodium alginate and calcium. In the most basic explanation I can give, here is how spherification works: Sodium alginate is a thickener until it comes in contact with calcium, the calcium makes it gel. So when the little droplets made of sodium alginate come into to contact with a calcium bath they become encapsulated immediately. But there is another type of spherification that is popular and we get many questions about it. This type of spherification contains no calcium or sodium alginate. So it’s not uncommon for us to get the question in our inboxes
“Can’t you just use agar to make spheres?”
Cold as Ice
The answer to the question above technically is yes. But the spheres made from agar are only similar to the spheres made with sodium alginate in that they are spherical. The method of spherification that is known as “cold oil” spherification is quite different than the method used for traditional spherification. Cold oil spherification is where you take a gelling agent (most commonly agar) and add it to your flavorful liquid. You will then need to heat it up to a boil before dropping little droplets into a container of ice cold oil. When the droplets hit the cold oil they will solidify due to the temperature change.
How this differs from sodium alginate spheres is there is no need for a second ingredient. You use the gelling agent, in this case it is agar. Chill the oil and begin making the spheres. They differ from sodium alginate spheres because you will never have a liquid center. This isn’t necessarily a worse method, just different in the end result. These spheres can be mixed into cocktails, after a rinse to remove any excess oil. They could also be mixed into a warm sauce to give a rather striking appearance.
Here are a few tips and tricks to help you make cold oil spherification. Be sure to use refined oil for forming the spheres, do not attempt to use olive oil or it will solidify when you pop it in the freezer. If you want you can store the pearls in a flavored or unrefined oil. These spheres will become waterlogged if you attempt to store them in a water based liquid, so just stick with oil, trust me.
The one downfall of this method is you will never have spheres that have a liquid center. So if you are looking to make spheres that burst when you eat them, this is not the method to do so. However it will make beautiful solid spheres.
Pro Tip: The Gelation Station
One thing I love about this method is the ability to use any gelling agent. Most commonly agar is used, but to be honest agar has poor flavor release and texture compared to some other gelling agents. Gellan gum F happens to be my favorite for this method because of the clarity you can get from the gel. If you want a different texture you can use any hydrocolloid that gels. I would suggest not using gelatin as it takes too long to gel and would just sink to the bottom of the oil and begin to stick together.
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