採取時期を異にしたマクサ(Gelidium amansii LAMOUROUX)から抽出した寒天ゲルのレオロジ-的研究

概要

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The rheological difference between the agar-agar gels prepared from Makusa (Gelidium amansii) gathered in spring and summer was examined on the basis of vibrational, stress relaxational, and ultrasonic measure- ment. Relaxation curves up to 10hrs for the gels containing 1-5wt% of agaragar were obtained in the temperature range from 25°C to 73°C. The melting temperature of the gels and the intrinsic viscosity of the aqueous solutions were also determined. The summer seaweeds contain larger amounts of sulfate residues than the spring seaweeds. Judging from the values of the intrinsic viscosity, the molecular weight of the agar-agar extracted from summer seaweeds was larger than that from spring seaweeds, The gels prepared from the summer seaweeds show greater values of relaxational modulus, storage modulus and melting temperature than the gels prepared from the spring seaweeds. In the concentrated gels the relaxation spectrum shows a greater value in summer seaweeds than in spring seaweeds at the longer time scale. In the lower concentration, there was not so much greater difference for the relaxation spectrum between the summer seaweeds and spring seaweeds. Therefore, it was suggested that at higher concentration, the molecular weight plays a dominant role in the gel formation, and at lower concentration, the sulfate residue content is also an important factor in the gel formation.
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