Understanding the effect of time, temperature and salts on carrageenan extraction from Chondrus crispus

Abstract

Alkali-free carrageenan extraction was performed on dried (around 1 cm size chips) gametophytic and tetrasporophytic Chondrus crispus at varying time and temperatures. For the gametophyte seaweed (containing κι-hybrid carrageenan and its precursors) the first 24 h extraction at room temperature resulted in an almost unrecoverable amount of carrageenan-rich precipitate (CRP) (1.6 ± 0.6 wt% of dry seaweed mass). A higher CRP yield was obtained (6.1 ± 0.6 wt% of dry seaweed mass) when a subsequent 24 h extraction was performed. Washing the gametophyte seaweed for 30 min with demineralized water prior to the first 24 h extraction reduced the conductivity of the seaweed dispersion and surprisingly improved its CRP yield (5.8 ± 0.1 wt% of dry seaweed mass). For tetrasporophytic C. crispus (λ-carrageenan) the first 24 h extraction at room temperature already resulted in a considerable CRP yield (18.6 ± 1.7 wt% of dry seaweed mass) despite the high conductivity of its seaweed dispersion. The CRP yield of gametophytic C. crispus improved with increasing extraction temperature. In the mentioned range of temperature, the maximum yield was obtained after extraction at 90 °C for 8 h (39.2 ± 0.0 wt% of dry seaweed mass). Finally, we observed at 60 °C that addition of different salts to the extraction dispersion prevented carrageenan from being extracted, with calcium salt showing the highest inhibitory effect.