Changes in volatiles and sensory profiles during storage of dried Ulva fenestrata: Effects of pre-rinsing and drying temperatures in a large-scale setting

Journal article, 2026

Large-scale oven drying was investigated as a stabilising method for Ulva fenestrata, focusing on odour, taste, volatile organic compounds (VOC), and colour during 550 days of storage. Sea-farmed biomass was either rinsed with tap water or antioxidant solution (AO) prior to drying at 40 °C or 60 °C. During storage, all samples showed an increase in a*-values and percieved loss of greeness, consistent with chlorophyll loss. However, AO-rinsing with 60 °C-drying best preserved colour, with only a 10 % loss of chlorophyll and 15 % reduction in greenness as assessed by the sensory panel. The flavour profile changed over time, especially in non-AO-treated samples, with a decline in seaweed odour, and appearance of “hay-like” and “rosehip soup” notes. In contrast, umami taste remained unchanged regardless of treatment, which was also true for amino acid content. Key VOCs were pentanal, hexanal and heptanal, however, each following a different kinetic pattern during storage. Drying at 40 °C led to greater VOC-formation and green colour loss than 60 °C + /-AO. As an example, hexanal, concentrations were almost 90 % higher after drying at 40 °C versus 60 °C, in both non-rinsed and water-rinsed samples. Altogether, drying at 60 °C is recommended, preferably combined with AO-rinsing if seaweed smell is desired.