Effect of alkali treatment time and extraction time on agar from Gracilaria vermiculophylla

Agar extraction from integrated multitrophic aquacultured Gracilaria vermiculophylla: Evaluation of a microwave-assisted process using response surface methodology

“…For wild G. vermicul-ophylla, Villanueva et al (2009) reported a content of 3,6-AG (42.5 ± 0.9%), in the agar traditionally extracted, similar to that of the agar obtained in this work with MAE. These results are also in agreement with those presented by Arvizu-Higuera et al (2008) for the same wild species collected in Mexico (44.4 ± 0.7%). Pearson's correlation analysis revealed that all gel properties were correlated positively with 3,6-AG content (gel strength, r = 0.67 (p < 0.01); gelling r = 0.70 (p < 0.01) and melting r = 0.64 (p < 0.01) temperatures), except the sulfate content which was negatively correlated (r = -0.81 (p < 0.01)).…”

“…New populations of G. vermiculophylla seaweed are new established in Ria de Aveiro (northwestern Portugal), and con-sequently, intensive studies are being conducted to the best knowledge and potential use of this marine alga (Villanueva et al, 2009). Several studies were published concerning traditional extraction method of agar using G. vermiculophylla (Arvizu-Higuera et al, 2008;Mollet et al, 1998;Orduña-Rojas et al, 2008a,b;Villanueva et al, 2009). This species may also be used in IMTA sys-tems, which is in fact under study at the moment by Maria H. Abreu from CIIMAR and co-workers in Coelho & Castro Aquacul-ture, Rio Alto, Portugal, with promising results so far (unpublished data).…”

“…In addition, the tradi-tional agar extraction method from G. vermiculophylla grown in IMTA systems originated significantly lower yields when com-pared with biomass from the same species harvested directly from Ria de Aveiro, Portugal: 29.4 ± 0.9% (Villanueva et al, 2009). Orduña-Rojas et al (2008a,b) and Arvizu-Higuera et al (2008) reported optimum yields of 9.6% and 16.5%, respectively, for G. vermiculophylla using 1.5-2 h of extraction in boiling water. Fig.…”

“…15% lower gel-ling temperature (40.7 ± 0.2 °C) than agar extracted from the same biomass aquaculture samples by the traditional method (48.1 ± 4.2 °C) but, once again, a gain in reproducibility was achieved. Using a 2 h extraction with the traditional method, Villanueva et al (2009) reported gelling temperatures in the range of 31.0-35.8 °C for G. vermiculophylla harvested directly from Ria the Ave-iro (Portugal) and Arvizu-Higuera et al (2008) reported a maxi-mum gelling temperature of 37.8 °C. Orduña-Rojas et al, 2008a,b indicated 41.8 ± 3.6 °C as optimum gelling temperature for the same species and a lower value for Gracilaria longissima, 37.5 ± 2.0 °C, after a 1.5 h traditional extraction.…”

A review of extractions of seaweed hydrocolloids: Properties and applications

“…As shown in Table 3, the content of 3, 6-AG and gel strength (GS) in agar and carrageenan were significantly increased after the treatment. This treatment is carried out due to commercial demand which requires high gel strength (>800 g/cm 2 ) [59]. But there are some drawbacks regarding the treatment as the treatment eventually lowers the extraction yields, due to the degradation of polysaccharides which gives low molecular weight polymer [58,[60][61][62].…”