Oxidative stability of protein concentrates from the green seaweed Ulva spp.

Protein extracted from Ulva spp., a green seaweed, is gaining attention for food applications due to its promising amino acid composition. However, limited information is available on the oxidative status of these extracts upon their production, and on their oxidative stability during storage. This study investigated the oxidative stability of three protein concentrates (PCs) from Ulva spp. stored under dark and light conditions for 120 days. PCs were produced in pilot-scale from wild Ulva spp. (PC Wild) and from the corresponding pulp (PC Wild pulp). Because these pilot-scale PCs were brown, indicating loss of chlorophyll and oxidation, lab-scale processing of cultivated Ulva sp. (PC Cultivated) was carried out for comparison. PC Wild and PC Wild pulp showed increased levels of volatile oxidation products compared to the primary biomass, whereas PC Cultivated showed values similar to its primary biomass, indicating that the lab-scale process was less harsh than the pilot-scale process. Differences in processing or in the balance between pro- and antioxidants in the primary materials could have contributed to these observations. Under light storage conditions, both PC Wild and PC Cultivated showed a greater loss of monounsaturated fatty acids and all PCs had increased levels of oxidation, indicating photooxidation. Lipid hydroperoxide values and volatile compounds reached higher levels on day 0 than on day 120, pointing to a turnover of both primary and secondary oxidation products and likely formation of cross-linked complexes.