Effects of instrumental conditions and gel-preparative procedures on texture characteristics of agar gels were studied using force-deformation curves from an Instron Universal Testing Machine. Resolution of the variables -penetration speed, probe size, probe to gel area, Container size, concentration and dissolution time of agars, pouring, gelation and analysis temperatures, and age of gels prior to measurement, -allowed for adoption of a standardized method for texture evaluation. Inclusion of Chlorides of sodium or potassium depressed whereas calcium and magnesium enhanced the gelation capacities of agar. Regression analyses indicated no decisive correlation existed between viscosity, reflecting molecular weight, and the texture characteristics from 25 specimens of agar.
Quantitative and qualitative precipitin tests using antibodies prepared against specific carrageenans from Chondrus crispus were performed on carrageenans that were extracted from plants of known stages in the life cycle of various other species of red algae. Species from three genera in the family Gigartinaceae were studied and it was determined that specific anti-κ-carrageenan serum was precipitated by carrageenans that were extracted from gametophytic plants but not by carrageenans from tetrasporic plants. Carrageenans and related polysaccharides from several species outside of the family did not show this difference.KCl-soluble carrageenan from female plants precipitated less antibody than KCl-insoluble carrageenan, but the soluble fraction that was treated with alkaline borohydride precipitated as much antibody as the insoluble fraction. Alkaline-borohydride-treated λ-carrageenan also precipitated the anti-κ-carrageenan serum. Other polysaccharides that precipitated anti-κ-carrageenan serum include iota carrageenan and furcellaran.Evidence presented from the above precipitin reactions indicates that 3,6-anhydrogalactose is involved in the determinant site of the antigen.
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