Agar Agar, was generally discovered in 1658 by Tarazaemon Minoya and was extended to other oriental countries in the 16th and 17th centuries from Japan. It was the first phycocolloid, a gelling agent extracted from marine algae, used as a food additive in our civilization. It is extracted from red seaweeds, the Gelidium and Gracilaria species in particular, which encompass the coastlines of many continents.
It is extracted under mildly alkaline conditions, and the extract is purified by filtration through cellulosic media. The purified extract is allowed to cool and gel, and the resulting gel is subjected to pressure, causing it to exude all its water over time. This is known as the gel press method. The dried agar is the ground to the desired particle size and standardized to the desired application properties by blending.
What is it?
Agar occurs as a linear polysaccharide made up of galactose units that has very few sulfate groups. Agar consists of a mixture of agarose, a linear polymer, and agaropectin, which is a heterogeneous mixture of smaller molecules. The agarose molecule alternates D-galactose units and 3,6 anhydro L-galactose units linked with alpha and beta bonds. The agaropectin contains a high percentage(21%) of C-6 carbons on the anhydro unit that contain methoxyl groups and is believed to affect the gelation temperature. As the percentage of methoxyl groups increases, the setting temperature rises. Therefore, gelation occurs at temperatures far below the gel hydration(melting) temperature, a difference of nearly 60 degrees Celsius. This is called temperature hystersis and what makes agar such a unique hydrocolloid.
What do we use it for?
Traditionally, in the Orient, "natural agars" are in the form of strips and squares which are used at home to prepare classic Japanese dishes.and desserts, like Yokan. Lately, the agar that we see in out natural and dietetic food stores is produced commercially and is presented in the form of clear colored powders. These powders seem to produce a more consistent product and leads to many new modern techniques:
- cold-oil spherification (.8%)
- fluid gels (.6% to 1.2%)
- cold clarification(.2%), hot clarification(2%)
- hot jellies (.2% to .5% )
- "noodles" ( .09% )
- disperse in cold liquid and heat while stirring until dissolved, above 90 degrees C.
- High hysteresis; forms gel at 35 degrees C.(95 F.) and melts at 95 degrees C.(203F).
- breaks down in hot acidic solutions; acid should be added after agar is added in neutral pH environment.syn
- not freeze/thaw stable.
- synergy with LBG (9pt agar:1pt LBG); this combination then used at 1% to 1.5% of total volume.
- prevents synersis with LBG.
- low viscosity solution.
.24% to 3%
<u>Further Reading/Research:</u> Hydrocolloids: Practical Guides for the Food Industry (Eagan Press Handbook Series), Andrew C. Hoefler, Martin Chaplin: Agar Agar, London South Bank University, web page.
--Daniel Campagna 13:06, 19 May 2011 (EST)