Agar-agar is prepared from hot water extracts of various species of Gelidium and differs somewhat in its composition according to its origin. It is sold commercially in the form of strips about eighteen inches long, varying in thickness from that of a straw to that of the finger. It contains about 60 per cent. of carbohydrates, principally in the form of galactosan and pentosan.
Saiki1 did a series of beaker experiments in order to determine its digestibility and obtained negative results, not only with saliva and pancreatic amylase, but also with an intestinal extract containing very active invertin. The digestibility was but little increased by preliminary treatment with dilute acid. He also found that agaragar was very resistant to the action of the ordinary intestinal bacteria. Only one of three strains of the
Bacillus coli communis caused gas production in agar-agar media, and that only to a slight degree.
MORSE JL. AGAR-AGAR IN THE TREATMENT OF CONSTIPATION IN CHILDHOOD. JAMA. 1910;55(11):934–936. doi:10.1001/jama.1910.04330110034010
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