Kristoffer Stedt1, Sophie Steinhagen1, João P. Trigo2, Gunilla B. Toth1, Karin Wendin3, 4, Ingrid Undeland2, Henrik Pavia1
1Department of Marine Sciences, Tjärnö Marine Laboratory, University of Gothenburg, Sweden
2Department of Biology and Biological Engineering – Food and Nutrition Science, Chalmers University of Technology, Sweden
3Department of Food and Meal Science, Faculty of Natural Sciences, Kristianstad University, Sweden
4Department of Food Science, Section for Food Design and Consumer Behaviour, University of Copenhagen, Denmark
Seaweed aquaculture can provide the growing population with a sustainable source of proteins. Sea-based cultivation is an effective method for farming seaweeds on a large scale and can yield high biomass output. The quality and biochemical composition of the biomass is however seasonally dependent, which limits the harvests to certain periods of the year. This study investigates the possibility to extend the sea-based cultivation season of Scandinavian Ulva fenestrata, aimed for food and feed production. We do this by cultivating U. fenestrata, harvested at sub-optimal summer period (with regards to its protein content), in herring production process waters as a post-harvest treatment in onshore tank systems. After 14 days, biomass yields were 30 – 40 % higher in the process waters (213.33 – 228.67 g fresh weight (fw)) compared to in seawater (162.67 g fw). The crude protein content increased by 3 – 4.5 times, from 3.76 % to 11.98 – 16.92 % dry weight (dw). Furthermore, the total amino acid composition (15.30 – 20.69 % dw) indicates that the crude protein content conversion factor of 5 underestimates the true protein content of the biomass. We show that the cultivation of U. fenestrata in herring production process waters generates protein-rich biomass, following food graded standards for heavy metal content. Additionally, no negative sensory attributes compared to when cultivated in seawater were found. The post-harvest treatment extends the cultivation period of U. fenestrata in sea-based cultivations, maximizing the output of sustainably farmed protein-rich biomass.