Trine Kastrup Dalsgaard1,4,5, Louise Juul1,4, Signe Hjerrild Nissen1,4, Ana Julia Valnion1, Marianne Hammershøj1,4,5, Annette Bruhn2, 4, Morten Ambye-Jensen3,4
1 Department of Food Science, Aarhus University, Agro Food Park 48, 8200 Aarhus N, Denmark
2 Department of Ecoscience, Aarhus University, CF Møllers Alle 3, 8000 Aarhus C, Denmark
3 Department of Biological and Chemical Engineering, Hangøvej 2, 8000 Aarhus C, Denmark
4 Centre for Circular Bioeconomy (CBIO), Blichers Allé 20, 8830 Tjele,Aarhus University, Denmark
5 Centre for Innovative Food Research CiFood, Agro Food Park 48, 8200 Aarhus N, Denmark
Sea lettuce (Ulva spp.) harvested in a Danish Fjord was processed in lab and pilot scale. The main goal was to extract protein from the biomass and evaluate it according to yield and food quality. The biomass crude protein content ranged between 6 and 20% of dry matter, concentrating up to 4-fold upon processing with double screw pressing followed by acid precipitation and centrifugation in pilot scale. Depending on season, the protein concentrate showed between 40 and 50% protein of dry matter. Washing of the biomass before processing lowered the ash content in the protein concentrates. The protein concentrates from the pilot study were evaluated in relation to functional properties and in meat analogues in combination with pea protein isolate (PPI). Solubility, foaming and gelling of Ulva protein fractions and PPI were investigated at food relevant pH conditions and a salt concentration of 0.2 M. Solubility of all protein fractions was low (< 20%) but alkaline pH-shift increased the solubility significantly. Depending on the pH, the foaming capacity was either significantly lower or higher, when compared to control. In general, the foam stability increased for PPI and Ulva fractions after alkaline pH-shift. Gelling properties of Ulva protein were assessed at 10% and 30% substitutions in 20% PPI gels. Rheological measurements revealed significantly increased gel strength and stability at 10% substitution. At 30% substitution, gel strength increased significantly but stability decreased. However, the processing needs further improvement for utilising the biomass for food.