Ms Cecilie Bay Wirenfeldt1,2, Dr Ditte Baun Hermund1, Dr Aberham Hailu Feyissa1, Dr Grethe Hyldig1, Dr Susan Løvstad Holdt1
1DTU Food, Lyngby, Denmark, 2NTNU, Department of Biotechnology and Food Science, Trondheim, Norway
Seaweeds contain 80-95% water, which makes them a highly perishable food product. Drying is used to stabilize foods by removing water, thus increasing their shelf-life. However, the drying method influences the end-quality: chemical, sensory- and physico-chemical properties. The two seaweed species Ulva spp and Fucus vesiculosus are growing as wild populations in the Danish inner waters and are of industrial interest for the use of food production. This study aimed to investigate different drying methods and evaluate their impact on the end-quality of the selected seaweeds.
The methods investigated were hot air drying (50 °C, 1 atm), freeze-drying (-40 to -10 °C, 20 Pa), and microwave-vacuum drying (-40 °C, 10 Pa).
Results showed that the drying methods changed the quality of the seaweeds differently. The F. vesiculosus dried by microwave-vacuum resulted in a lower water content than Ulva spp dried by the same method. In addition, water absorption showed that Ulva spp absorbed twice as much water as F. vesiculosus, explaining why Ulva spp was more resistant to dry (long drying time). Hot air drying and microwave-vacuum drying preserved the valuable pigment fucoxanthin in F. vesiculosus, whereas freeze-drying did not. Sensory profiling also showed that the drying methods did not change the sensory for F. vesiculosus, but the drying methods changed the sensory of Ulva spp (had different profiles between the drying methods).
Overall, we concluded that the choice of drying method affects the overall quality of the dried seaweeds and that one drying method might be more suitable for one type of seaweed than the other.