João P. Trigo1,*, Kristoffer Stedt2, Alina E. M. Schmidt3, Barbro Kollander4, Ulrica Edlund3, Göran Nylund2, Henrik Pavia2, Mehdi Abdollahi1, Ingrid Undeland1,*
1Department of Biology and Biological Engineering – Food and Nutrition Science, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden
2Department of Marine Sciences, Tjärnö Marine Laboratory, University of Gothenburg, Laboratorievägen 10, SE 452 96 Strömstad, Sweden
3Fibre and Polymer Technology, KTH Royal Institute of Technology, SE 100 44 Stockholm, Sweden
4Livsmedelsverket – Swedish Food Agency, Dag Hammarskjölds väg 56 A, Uppsala, Sweden
The seaweed Saccharina latissima is often blanched to lower iodine levels, however, it is not known how blanching affects protein extraction. Therefore, we assessed the effect of blanching or soaking (80/45/12°C, 2 min) on protein yield after pH-shift processing of S.latissima. We also examined the influence of all water treatments and pH-shift processing on the protein/peptide size distribution and chemical composition, including elemental analysis, of biomasses and protein extracts thereof.
Average protein yields and extract amino acid levels ranked treatments as follows; blanching-45°C ~ control > soaking ~ blanching-80°C. Although blanching-45°C decreased protein solubilization yield at pH 12, it increased isoelectric protein precipitation yield at pH 2 (p<0.05). Analysis of the protein/peptide size distribution revealed a higher ratio of large peptides/proteins in the blanched biomass, which could explain the lower protein solubilization yield after blanching. Also, through a dialysis model, we confirmed a link between lower ionic strength after blanching and increased protein precipitation yield. Regarding elemental composition, blanching-45°C yielded a protein extract with 49% less iodine compared with the control extract from non-treated S. latissima. Non-essential elements such as cadmium, lead, and nickel were concentrated after blanching treatments. Nevertheless, iodine is still the element limiting consumption at higher amounts of all biomasses and respective protein extracts. The monosaccharide profile revealed that the up-concentration of those non-essential elements was probably due to an increased proportion of alginate after blanching.
We recommend blanching at 45°C since it is effective at removing iodine and does not compromise total protein extraction yield.