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Although agar has only recently emerged as a common gelling agent in modern western kitchens, it has been used in asian countries for centuries as their go-to gelling agent. A polysaccharide derived from red algae, agar is a great alternative to gelatin when a vegan or vegetarian gel is needed, or when attempting to gel liquids that normally will break down gelatin because of low pH, high alcohol, or proteolytic enzymes in fresh fruits.
One of the unique qualities of an agar gel is “hysteresis,” meaning there’s a large differential between agar’s setting and melting temperature (95°F/33°C and 175°F/80°C respectively). This makes it possible to serve a warm gel using agar, something that isn’t possible with traditional gelatin based gels.
Agar also sets rapidly above room temperature (95°F/33°C), within a matter of minutes, as opposed to gelatin, which takes 12-24 hours to fully set, once it’s core reaches 59°F/15°C.
The appearance of an Agar gel can range from clear to opaque, depending on what’s being gelled and the quality of the agar, and has a texture that ranges from firm to brittle. If too much agar is used to set a gel, the texture can become “crumbly” and unpleasant, especially since the heat from our mouth is well below it’s melting point.
However, an agar gel can be made less brittle and given an elastic texture with the addition of sorbitol or glycerol, usually around 1% by the weight of the entire gel being set.
One of the big advantages to using an agar gel is its low pH tolerance, with a range of 2.5-10. This makes it possible to set acidic terrines and gels, and is what we used last winter to create a seasonal citrus terrine with a pH of 3.2. This could not be achieved by using gelatin with its pH tolerance of 4-10.
Agar can also create what’s called a “fluid gel;” in this application it’s first allowed to set, and then blended smooth in a blender. When transforming a liquid with the viscosity of water into a fluid gel, usually .3% agar is added (based on the liquids weight), hydrated, allowed to set, and then blended smooth.
For more information, please refer to our next post in our Agar series, “How to Create an Agar Gel Plus Common Pitfalls.”
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