Sensory aspects and consumer attitudes and preferences of sea lettuce (Ulva fenestrata): impact of protein level, harvest time and cultivation conditions

Seaweed is a promising source of sustainable future food containing high quality proteins. Protein content and other qualities of farmed sea lettuce (U. fenestrata) are dependent on cultivation conditions and treatments. To provide sustainable and tasty seaweed products, consumers’ experience and attitudes are important. Although consumers are generally positive toward seaweeds as food an increased understanding of sensory qualities of seaweeds in food applications need to be explored. The aim was to explore sensory qualities and consumer attitudes of the sea lettuce and the impact of cultivation conditions, harvest time and protein content. Sea lettuce was cultivated in three settings: i) sea-based farm, ii) land-based tank with sea water and iii) land-based tank with salt brine from fish processing industry. Harvesting occurred at three different time points and crude protein content was measured. After drying and milling, the seaweed was mixed into 5% o/w emulsions forming 9 samples. Whole dried seaweed leaves formed another 9 samples. All samples were evaluated by a trained analytical sensory panel. In addition, three samples (one from each cultivation type) were assessed by consumers. Cultivation of sea lettuce with addition of salt brine gave a crispy texture. A later harvest time increased sourness. High protein content increased saltiness and intensity of green colour. A major part of the sensory attributes expressed both for whole leaves and for emulsions, respectively, correlated significantly with each other. However, the emulsions seemed to pronounce the sensory attributes, which may be of importance when developing food products. The general sensory description of sea lettuce as food is coherent with earlier studies of Ulva species. However, the impact of cultivation, harvest time and protein content on sensory qualities of sea lettuce have not been investigated in earlier studies. In line with other studies, Swedish consumers appreciated the seaweeds as food.