Characterization of Carrageenan Extracted from Hypnea bryoides in Oman
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Carrageenophyte red seaweed from Oman, Hypnea bryoides, extracted using three different processes: an aqueous, a mild alkaline, and a more vigorous alkaline extraction was investigated. The resulting extract precipitated by alcohol was subject to chemical and rheological measurements. The total carbohydrate [ranged from 36.78 to 41.65 g/100 g], and ash [39.04 to 43.11 g/100 g] were the most abundant components in H. bryoides and contrary to the two, lipid content was found at a minimum [ranging from 2.95 to 3.38 g/100 g]. Alkali treatment with NaOH allowed complete conversion of kappa (κ) carrageenan form as detected by FTIR analysis. Total yield by alkali treatments gave higher yields (33%) compared with aqueous treatments (12%). However, subsequent aqueous treatment produced mixed carrageenan (μ and κ) with higher molecular weight compared with the alkali treatments which produced single carrageenan form (κ) with molecular weight of 4.1 × 105 Da. The effects of thermal history on gel–sol and sol–gel transition were investigated by differential scanning calorimeter (DSC) and rheology on a pure sample and 1.5% κ-carrageenan mixture added with 30 mM KCl. Transition temperatures from DSC and rheology showed comparable results and were in good agreement with those previously reported.
KeywordsHypnea bryoides Algae Seaweed Phycocolloids FTIR
This work was supported by HM Sultan Qaboos Trust Fund (SR/AGR/FOOD/05/01, PI: B Soussi), University of Gothenburg and the Swedish Research Council (K2005-73-00536, PI: B. Soussi). The authors thank Barry P. Jupp for the valuable discussions; Rabea Al Maqbaly, and Suleiman Al Sheili for their technical assistance.
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