Turkish Journal of Biology

Seasonal Variation in Chemical Constituents of Unextracted Material (Residue) of Gracilaria Verrucosa, After the Extraction of Agar


Muhammed ILYAS




The utilization of algae, particularly from wild stock, as a source of agar is becoming increasingly uneconomical. No alternative is yet available. The phyccocolloid industry depends on algae as the sole source of agar. Many steps have been taken to make it more economical, including the extraction of intermediary metabolites. The present study is the first of its kind on algae collected from the Agean sea (Turkey-Izmir). The unextracted material of algae was recovered during the agar extraction process and called residue. It was at a maximum during the months from November to April (excluding January). The residue was analyzed for organic and inorganic components throughout the year of collection. Inorganic components included ash [soluble (water/acid) and insoluble] Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn. Organic components included protein, lipid, crude fiber and NFE (Nitrogen Free Extract). Different energies (gross, calculated, metabolized) were also computed. An aminoacid profile was determined in the samples of maximum protein value. A thorough analysis of residue throughout the year suggested that the residue colud be used as a feed ingredient itself or as a raw material for the extration of protein.


Agar extraction process, Unextracted material, Protein sources, By-product, Feed ingredient

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