Mar Vall-llosera Juanola1, Sophie Steinhagen2, Henrik Pavia2, Ingrid Undeland1
1Chalmers university of technology, Biology and biological engineering – Food and Nutrition Science, SE412 96 Gothenburg, Sweden, 2Department of Marine Sciences, Lovén Centre for Marine Sciences – Tjärnö, University of Gothenburg, SE-452 96, Strömstad, Sweden
Green seaweed, such as Ulva spp., has become of interest to the aquaculture industry because of its resilience to nutrient, salinity and temperature variations. However, the biomass rapidly perishes after being harvested due to its high moisture content and abundance in compounds stimulating microbial growth, e.g. cellulose. Thus efficient yet mild methods to preserve the quality of Ulva spp. are needed to facilitate its use as a food ingredient. In the BlueGreen project, tailor-made methods are developed for stabilizing Ulva spp. biomass in terms of its microstructure, texture, colour, volatile compound profile and nutritional properties. In this specific sub-project, brining of Ulva fenestrata was in focus, an area where very little research has been done.
Fresh Ulva fenestrata was subjected to analyses of nutrients (e.g., proteins, fatty acids), colour, texture, pH, salinity, and microbial load. For brining, the biomass was then placed in sealed containers at brine to seaweed ratios of 1:10. The brines were prepared with salt concentrations varying from 2-26 Brix°. The Brix° of the brines, as well as water activity, protein content, fatty acid composition, colour, microbiological load and tensile strength of the U. fenestrata, were then monitored over 2 months or until spoilage occurred. For the microbial load analyses, plate count agar and Marine agar were incubated at 25°C, and Long and Hammer agar were set at 15°C. The colonies were counted, isolated and Gram stained to identify, tentatively, the microorganism on the different brines over time.
Preliminary results reveal that U. fenestrata in salt brines ≥15 Brix° remained at a low coliform counts for >40 days, and the water activity of the seaweed was reduced from the native 0.94 to 0.85. However, salt brine, with 26 Brix°, was needed to retain the greenness of the Ulva blades. Additional results on e.g., microbiology, nutrient composition and volatile compounds will also be presented and discussed.