Studies on Tanzanian hypneaceae: seasonal variation in content and quality of Kappa-Carrageenan from Hypnea musciformis (Gigartinales : Rhodophyta)
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Seasonal effects on yield and quality of kappa-carrageenan from the red alga Hypnea musciformis were investigated in samples collected from natural populations in Oyster Bay, Dar es Salaam during June 1996–May 1997. The mean annual carrageenan yield, gel strength (after treatment with 0.1 M KCl) gelling and melting temperature (± standard deviation) were 25.24 ± 4.44 % dry weight, 171.72 ± 41.42 g/cm2, 54.66 ± 3.12 ºC and 68.62 ± 0.60 ºC, respectively. Carrageenan yield and quality (gel strength) during the SE and NE monsoon seasons were not significantly different (t = 0.55, p > 0.05) and (t = 1.91, p > 0.05), respectively. The reported carrageenan yield and gel strength values were, respectively, about 50% and 40% those of carrageenan from Kappaphycus alvarezii. Although the carrageenan properties from H. musciformis were promising, its natural populations are generally insufficient to sustain the pressure of economic harvesting. Moreover, the extent to which its carrageenan yield and properties could be improved is not known. Suitable methods for mariculture are therefore needed before the resource can be exploited economically.