Sea lettuce (Ulva fenestrata) as a rich source of cobalamin (vitamin B12) – both as processed whole biomass and as an extracted protein ingredient

The seaweeds Ulva fenestrata and Palmaria palmata are promising food items; however, it remains unclear whether both contain true vitamin B12 and how post-harvest processing, storage, and protein extraction affect this vitamin. UHPLC-UV-MS/MS analysis revealed that untreated Ulva contained 681 ± 37 ng B12/g dry weight (dw) - 22 times more than Palmaria. Biomass soaking (16 °C, 3 min) in freshwater did not affect B12 content, but blanching (60 °C, 3 min) reduced its content in Ulva by 45 % (dw basis) and 61 % (protein content basis). Oven-drying and freeze-drying equally preserved B12; both techniques maintained B12 content during room-temperature dark storage for 4.8 months. Protein extraction via a new method (Trigo et al., 2025) resulted in a dried ingredient containing 60 % more B12 than untreated Ulva, and 29 times more than red meat on a moisture-equivalent basis. All Ulva samples - including the protein ingredient - qualified for the EU nutritional claim "High in Vitamin B12".