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

The green seaweed Ulva fenestrata is a future food candidate, however, both compositional, e.g. protein content, and sensory qualities depend on cultivation and harvest conditions. The aim was to explore sensory qualities of, and consumer attitudes to, U. fenestrata derived from three different cultivation conditions and three harvest times. U. fenestrata was cultivated at sea and in two different land-based tank settings, one mimicking seawater and one with added process water from fishing industry to increase protein content. The seaweed was subjected to sensory analysis performed by an analytical sensory panel and a focus group consisting of consumers. The former assessed the seaweed as dried whole blades (9 samples) and as emulsions (9 samples). Consumers assessed whole blades and a vegan spread enriched with powdered U. fenstrata. All seaweed samples were intensely green; had tastes of umami, salt, bitter, and sour; odours and flavours of grass and fresh seaweed; and had a crispy texture. Cultivation in tanks resulted in a crispier texture than sea cultivation (p<0.001). Protein content increased from 14.4% to 21.6% in tank cultivation with process waters, which increased green colour intensity (p<0.007) and decreased intensity of bitterness (p<0.001). Overall, consumers were positive towards seaweeds as foods.