Effects of preservation on protein extraction in four seaweed species

Using either freshly pulped or preserved seaweed biomass for the extraction of protein can have a great effect on the amount of protein that can be extracted. In this study, the effect of four preservation techniques (frozen, freeze-dried, and air-dried at 40 and 70 degrees C) on the protein extractability, measured as Kjeldahl nitrogen, of four seaweed species,Chondrus crispus(Rhodophyceae),Ascophyllum nodosum,Saccharina latissima(both Phaeophyceae) andUlva lactuca(Chlorophyceae), was tested and compared with extracting freshly pulped biomass. The effect of preservation is species dependent: in all four seaweed species, a different treatment resulted in the highest protein extractability. The pellet (i.e., the non-dissolved biomass after extraction) was also analyzed as in most cases the largest part of the initial protein ended up in the pellet and not in the supernatant. Of the four species tested, freeze-driedA. nodosumyielded the highest overall protein extractability of 59.6% with a significantly increased protein content compared with the sample before extraction. ForC. crispusextracting biomass air-dried at 40 degrees C gave the best results with a protein extractability of 50.4%. Preservation had little effect on the protein extraction forS. latissima; only air-drying at 70 degrees C decreased the yield significantly. Over 70% of the initial protein ended up in the pellet for allU. lactucaextractions while increasing the protein content significantly. Extracting freshly pulpedU. lactucaresulted in a 78% increase in protein content in the pellet while still containing 84.5% of the total initial total protein. These results show the importance of the right choice when selecting a preservation method and seaweed species for protein extraction. Besides the extracted protein fraction, the remaining pellet also has the potential as a source with an increased protein content.