G. Hernandez-carmona et al., Pilot plant scale extraction of alginate from Macrocystis pyrifera. 1. Effect of pre-extraction treatments on yield and quality of alginate, J APPL PHYC, 10(6), 1998, pp. 507-513
In the extraction of alginate from brown seaweeds, the acid pre-extraction
treatment has been considered by many authors as an essential step because
it makes the alginate more readily soluble in an alkaline solution. At pilo
t plant level, extractions were made (i) using formalin treatment prior to
the acid pre-extraction treatment (ii) using different acid treatments so t
he calcium ions exchanged varied from 83% to 4%. The use of formalin treatm
ent gave a product with less color. During the acid pre-extraction treatmen
t, it was possible to reduce the calcium exchanged from 33.4% to almost zer
o with a maximum reduction in alginate yield of 7%. The degree of acid trea
tment was positively correlated to calcium exchanged and yield but negative
ly correlated with alginate viscosity. Using strong acid conditions the vis
cosity was 168 mPa s, while mild acid conditions produced an alginate with
623 mPa s. The direct extraction from calcium alginate to sodium alginate i
s possible because strong alkaline conditions were used, pH 10 at 80 degree
s C for two hours and with a low water volume. The best pre-extraction trea
tment to obtain an alginate with high viscoity is to hydrate the alga with
0.1% formalin overnight, then wash the alga once with hydrochloric acid at
pH 4 using a batch system with continuous agitation during 15 min.