Abstract
Seaweed Kappaphycus alvarezii previously known as Eucheuma cottonii is one of the best sources of kappa carrageenan and is cultivated in Philippines, Indonesia, Malaysia and other countries including India. In the present study, semi-refined carrageenan (SRC) was prepared from K. alvarezii with different concentrations of KOH (6, 12, 18 and 24%) at 80 ± 2°C for 2 h; its sulfate contents were 13.73±0.74, 13.66±0.27, 13.84±0.66 and 14.76±0.18%, respectively, and it was 14.10±0.34% for untreated clean weed (control). The sulfate removal with increasing concentration of KOH used for processing SRC is not statistically significant (p < 0.05). The KCl gel strength of untreated clean weed and 6, 12, 18 and 24% KOH treated weed was 97±10.27, 650±12.11, 637±10.25, 552±18.71 and 526±26.55 g cm-2, respectively. Contents of 3,6-anhydrogalactose were 28.30±0.52, 33.41±0.50, 32.97±0.42, 31.15±0.60 and 31.61±0.17%. FTIR spectroscopy showed that molecules in all four SRC samples are quite similar. Spectral band was at 1257 cm-1 which referred to ester sulfate of 930 cm-1 for 3,6 anhydrogalactose and 848 cm-1 assigned to galactose-4-sulfate. From the present investigation, it was observed that sulfate removal and quality improvement with increasing concentration of KOH for cooking seaweed is not statistically significant; therefore, seaweed can be subjected to lower concentration of KOH treatment (6 to 12%) to produce semi-refined carrageenan on commercial scale. Key words: Seaweed, Kappaphycus alvarezii, KOH treatment, semi-refined carrageenan (SRC), sulfate content, FTIR spectra, gel strength.
Highlights
Carrageenans are sulfated linear polysaccharides extracted from certain red seaweeds of the classFlorideophyceae
Seaweed Kappaphycus alvarezii previously known as Eucheuma cottonii is one of the best sources of kappa carrageenan and is cultivated in Philippines, Indonesia, Malaysia and other countries including India
Spectral band was at 1257 cm-1 which referred to ester sulfate of 930 cm-1 for 3,6 anhydrogalactose and 848 cm-1 assigned to galactose-4-sulfate
Summary
Carrageenans are sulfated linear polysaccharides extracted from certain red seaweeds of the class. They have been extensively used in the food industry as thickening and gelling agent and more. The quantitative analysis of carrageenan or semi-refined carrageenan (SRC) batches is of greatest importance for industry to deliver a standard product and to develop new application based on their unique intrinsic properties. Farming of tropical seaweed Kappaphycus alvarezii Doty (Doty) (previously known as Eucheuma cottonii) in Indian water has been going on for more than a decade (Krishnan and Narayanan, 2010), and Kappaphycus is extensively used for the industrial production of κ-carrageenan (Glicksman, 1983; Hoffmann et al, 1993). SRC was mainly used in pet food and other applications where clarity was not an important criterion. Recently there has been improved method to produce SRC of food grade for human consumption
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