Abstract:

The storage condition of dried wakame, which contained 57.9% alginate, with a D-mannuronic acid to L-guluronic acid ratio of 1.92, was investigated. The water sorption isotherms of dried wakame and sodium alginate qualitatively resembled each other, but showed slight qualitative difference above A_w 0.70. The amounts of water absorbed in a monomolecular layer of dried wakame and sodium alginate were 4.4 and 5.1 (g H₂0•100 g^-1 solids), respectively. It was suggested from the results obtained in this study that the water absorption of dried wakame was attributable to the presence of alginate, the main structural component of wakame.
From the differential scanning calorimetry (DSC) thermograms of dried wakame and sodium alginate, only a single endothermic peak was observed between 20 and 90ºC for both samples. The endothermic peak temperatures decreased linearly with increasing water activity. The degradation of chlorophyll followed pseudo-first order reaction. The rates of chlorophyll degradation profoundly faster above the DSC endothermic peak temperature of wakame compared with those below the endothermic peak temperature, suggesting that the stability of chlorophyll in wakame depends largely upon the state of alginate.

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Date 1996/12/01

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