Bioactive compounds in farm-raised sea vegetables

Bioactive compounds in farm-raised sea vegetables

Summary

Sea vegetables consumption has seen an increase in the West, partly due to growing awareness of their health benefits. Bioactive compounds are often associated with various health promoting effects including high antioxidant capacity, anti-inflammatory, anti-cancer and anti-aging. Sea vegetables are considered to be high in bioactive compounds, and this project aims to focus specifically on total phenolic content (TPC) and antioxidant capacity of fresh farm-raised sea vegetables grown in Maine. Effects of minimal processing such as blanching and freezing on bioactive compounds in sea vegetables are poorly investigated. Moreover, the amount of bioactive compounds present in sea vegetables can vary within different parts such as blade versus stipe. Therefore, this research project will assess the effects of minimal processing treatments (blanching/freezing) and source of edible plant tissue (blade/stipe; in species where there is a clear distinction between their parts) on Sugar kelp, Dulse, Alaria and Gracilaria. The results of this project will provide sea vegetable farmers with information to market their products. Fresh, fresh frozen, blanched and blanched frozen samples will under go 1,1-diphenyl-2-picrylhydrazyl (DPPH), Ferric reducing antioxidant power (FRAP) and TPC analyses. A small consumer panel will be used to determine optimal blanching (80C for 1min or 100C for 5s) treatment for the sea vegetables under consideration. Blanched samples will be evaluated immediately after processing whereas the frozen samples will be stored at -20C for one month.

Objectives/Performance Targets

Objective 1: Determine total phenolic content (TPC) and antioxidant capacity in four species of fresh farm raised sea vegetables.

Objective 2: Determine the effects of minimal processing (blanching and freezing) on the stability of TPC and antioxidant capacity of the sea vegetables.

Objective 3: To determine if any significant differences exist in TPC and antioxidant capacity between blade and stipes of the sea vegetables.

Objective 4: To compare the data for farm raised products with data for wild harvested sea vegetables in the scientific literature.

 Objective 5: To communicate research results to interested members of the aquaculture and seafood communities in the Northeast region.

Accomplishments/Milestones

Objective 1: Literature review is in progress to inform development of appropriate methods to extract bioactive compounds from sea vegetables. In addition, methods for TPC, DPPH and FRAP are also being reviewed in the literature. In January 2016, multiple trials will be conducted to establish a robust lab protocol for all the above analyses.

Objective 2: We determined the optimal blanching methods (temperature and duration) based on sensory evaluation. Since it was October and the only crop available was Gracilaria, it was used to make seaweed salad after blanching by two different methods; 80C for 1min or 100C for 5s. Twelve panelists familiar with seaweed products conducted difference tests on the seaweed salad samples. Results showed that the panelists could not detect any significant difference between seaweed salads samples made with the two different blanching treatments. The 80 C for 1 min blanching treatment was selected based on two considerations; the sensory evaluation showed us that there were no detectable differences between the two treatments and because this specific treatment has been used previously to blanch sea vegetables (McHugh and (FAO) 2003; Boulom et al. 2014).

Gracilaria samples were received in early November. All the samples were immediately processed as fresh, fresh frozen, blanched or blanched frozen in triplicate. The fresh and blanched samples were immediately freeze-dried whereas both the frozen treatments were freeze-dried after 1 month’s storage. The fresh and blanched treatments will show immediate effects (if any) of processing and the frozen treatments will assess storage effects on minimally processed samples. At this point, all the Gracilaria samples are freeze-dried and stored at -80C until further analysis.

We are currently developing a protocol to conduct antioxidant (DPPH and FRAP) and total phenolic analysis. Three other species will be processed and analyzed, as the crops are available.

Note: Although the initial aim was to use aquacultured Gracilaria, due to failure of crop this season we used wild Gracilaria to continue the project.

Impacts and Contributions/Outcomes

Work on this project will start in full swing in Spring 2016.

Collaborators: