Abstract:
Seaweeds, Eucheuma cottonii, is widely recognized for its nutritional and industrial value due to
its high content of bioactive compounds, including carrageenan. In this study, E. cottonii was
sourced from the coastal area of Mannar, Sri Lanka, where it is cultivated by local seaweed
farmers. Carrageenan, a water-soluble polysaccharide, is extensively utilized in the food industry
as a gelling, thickening, and stabilizing agent. However, E. cottonii's dark brown color and odor
limits its food applications despite its valuable carrageenan and mineral content. This study
optimized decolorization methods to preserve gel strength while effectively removing color and
odor, thereby maintaining functionality. Three 3% solutions, hydrogen peroxide, sodium
metabisulfite andascorbic acid were tested in 24h ambient dips, followed by hot water extraction
at 70-75°C. Hydrogen peroxide exhibited the highest gel strength among the treatments, along
with effective decolorization. According to hedonic scale evaluation, it also achieved the highest
deodorization scores, indicating the greatest reduction in undesirable odor as perceived by
panelists. Further optimization trials tested H₂O₂ concentrations of 0.5%, 1%, and 3% over 24,
48, and 72 hours to determine the ideal balance between decolorization and gel strength. At 0.5%
H₂O₂, the 48-hour dipping method was identified as optimal, achieving effective decolorization
with an L value of 18.58 while maintaining a high gel strength of 0.18N. In contrast, extending the
treatment to 72 hours improved decolorization slightly (L value of 20.21) but significantly
reducedgel strength to 0.11N. This demonstrates that prolonged exposure beyond 48 hours
compromises gel strength despite increased color removal. Treatment duration was strongly
correlated with gel strength at 0.5% H₂O₂ (r = 0.912, p < 0.001), highlighting the critical role of
optimizing dipping time. Therefore, 48 hours was selected as the best treatment duration to
maximize decolorization while preserving the gel strength of E. cottonii, supporting its
application in developing high-quality food products.
