Effect of storage conditions on lipid oxidation, nutrient loss and colour of dried seaweeds, Porphyra umbilicalis and Ulva fenestrata, subjected to different pretreatments

Here we evaluated the levels of lipid oxidation products, fatty acids, ascorbic acid and colour of Porphyra and Ulva after oven-drying at 40 °C, and during subsequent storage for ≥370 days under light, semi-light and dark conditions. Part of the seaweed was pre-soaked in freshwater or pre-coated with a whey protein mixture. Controls consisted of freeze-dried seaweeds. Throughout storage there was a moderate development of the lipid oxidation-derived aldehydes, malondialdehyde, 4-hydroxy-trans-2-hexenal and 4-hydroxy-trans-2-nonenal, while there was a great loss of unsaturated fatty acids and ascorbic acid. Light storage and freeze-drying stimulated the fatty acid loss as well as pigment bleaching, seen as increased a*-values. For Ulva, the coating reduced malondialdehyde, 4-hydroxy-trans-2-hexenal and 4-hydroxy-trans-2-nonenal formation during drying and slightly prevented loss of polyunsaturated fatty acids during light storage. Pre-soaking in freshwater had no effect on the seaweed stability, although it reduced the ash content and thereby increased the relative content of ascorbic acid and fatty acids of the biomasses.