Hot water agar extracts were made from different phenotypes of Gracilaria salicornia and their chemical and physical properties studied. The highest agar yield (12-16% dry weight) was obtained from the phenotype that grows in bundles in intertidal muddy-rocky surfaces (ecotype B), while the lowest yield (6.5-7.8%) came from the phenotype that grows as cushions on exposed intertidal rocky surfaces (ecotype C). Gelling temperatures were generally higher in the extracts obtained from the intertidal phenotypes (ranging from 36 to 38-degrees-C) and lower in those obtained from the sublittoral phenotype (phenotype D) which ranged between 34 and 35-degrees-C. Conversely the melting temperatures were higher in the extracts obtained from the sublittoral phenotype than those of the intertidals. The highest gel strength of 240 g/cm2 was recorded from the extracts of phenotype C whereas the lowest, 78.7 g/cm2, was recorded from the exposed intertidal pool phenotype (A). Highest 3,6-anhydrogalactose and sulphate contents, 19.4 and 1.6% respectively, were recorded from agar extracts of phenotype C while phenotype B had the lowest sugar content (11.1%) and phenotype D the lowest sulphate content (1.25%). The effect of age on the different parameters measured varied from phenotype to phenotype. The influence of macro- and micro-habitats on the quality and quantity of agar from different phenotypes is discussed. |
