Carrageenan of Eucheuma isiforme (Solieriaceae, Rhodophyta) from Yucatán, Mexico. I. Effect of extraction conditions

The yield and physicochemical properties of carrageenan from Eucheuma isiforme harvested at the Yucatán coast were investigated. Carrageenan was extracted under different alkali concentrations (0, 1, 3, 5 and 7% KOH) and treatment durations (3, 4 and 5 h). Native carrageenan, extracted without KOH, had the highest yield (;44.6%) independently of treatment duration. After alkali treatment, carrageenan yield ranged from 35.3 to 31.8%. No significant differences in carrageenan yield were observed between 1 and 3% KOH. Native carrageenan had low viscosity values (39–57.0 cPs), whereas carrageenan extracted with 1% KOH at 3 and 4 h increased in viscosity (160.0–161.3 cPs). Alkali-treated carrageenan formed very weak gels (-50 g cm-2) in 1.5% solutions. The chemical analysis and FTIR spectra revealed a preponderantly iota-carrageenan extract. Extractions performed with 1% KOH for 3 h produced carrageenan with suitable properties to be considered as a substitute for traditional iota-carrageenan sources.