Angelina's Advice....

'Agar agar' is a gelatinous substance derived from seaweeds. It has wide traditional culinary uses but has become an important part of the bacteriology lab as well.

Robert Koch is widely regarded as a pioneer of microbiology. He was the first to culture bacteria on the surface of a solid medium. Initially, he used a medium solidified with gelatin. But gelatin tended to melt at slightly higher temperatures and it was not possible to incubate the plates at a higher temperature. Furthermore, many bacteria were capable of attacking gelatin and degrading it. Walther Hesse, an assistant of Koch’s related his difficulties to his wife Angelina. Fanny Angelina Hesse suggested that he try an ingredient which her mother had given her. This ingredient was given to her mother by some friends in Java, Indonesia, who used it frequently in making fruit jams and jellies. This ingredient was called agar agar.

Walther Hesse substituted gelatin for agar agar and found it to give excellent results. Once solidified, agar agar was capable of resisting temperatures above 50 degrees Centigrade. He also found that very few bacteria were capable of degrading agar agar and thus it could serve as an excellent solidifying, yet inert, agent. He conveyed his results to Robert Koch who used agar plates to isolate Mycobacterium tuberculosis. He published his results on 24th March 1882.

From then on, agar plates were widely used the world over for cultivating and isolating bacteria. They are also used to aseptically grow tissue-cultured plants or calluses. Agar agar has been used in Japanese culinary practices as a thickener for making jellies, custards and puddings. Some popular Japanese recipes that use agar are anmitsu and mizuyokan. Agar has also gained popularity (or notoriety) as a new get-slim diet known as the “kanten diet.”

Technically, Agar (China Grass, kanten or Japanese isinglass) is a polysaccharide made up of repeating galactose units. It is an unbranched polysaccharide obtained from cell walls of red algae like Gracilaria or Gelidium or from the seaweed, Sphaerococcus euchema. Commercially, however, it is obtained from Gelidium amansii. Agar agar has been used as a laxative, thickener in soups, jams, jellies and in traditional Japanese desserts. It is also used as a clarifier in brewing industries. Agar agar is also widely used to treat constipation. But studies have revealed that long term use of agar agar as a laxative for chronic constipation can lead to bowel obstruction and esophageal obstruction. It reduces absorption of vitamins, minerals and other nutrients.

Ref: Wolfgang Hesse, (Translatedby Dieter H.M. Groschel), Walther and Angelina Hesse early contributors to bacteriology, ASM news, Vol 58, No.88, 1992. Pg 425-428.