EFFECT OF ALKALI PRETREATMENT ON STRUCTURE AND PROPERTIES OF AGAR FROM PORPHYPA HAITANENSIS

This paper reports the changes in properties and structure of theagar from Porphyra haitanensis under various concentration of alkali-pretreatment.Having been treated with concentrated alkali, chemical component and rheologicalproperties of the solutions change remarkably. The content of sulfate ester (SO₃)decrease from 5.8% to 0.12% 3.6-anhydrogalactose increase from 6% to 44. 50%.the gel strength (g/cm²) increase from 0 to 761. It is suggested that the de-esteri-fication of sulfate residues increased the gel forming power. This is caused by the increase of hydrogen bond and of 3.6-anhydro-L-galactose. These two factorsmake agar molecules stablize of double helix structure. The IR spectrum and electron microphotograph show a great difference be-tween agar porphyra and porphyran. 13c-n. m. r. spectra of alkali treated porphyrapolysaccharide further show that the results of alkali treated is agar. This agar aswell as other agar is double helices formed the microcrystalline structure.