아임계 수 및 초임계 이산화탄소로 처리된 진주담치 (Mytilus edulis) 추출물의 물리화학적 특성 및 생리활성 평가

Abstract

Blue mussel (Mytilus edulis), which is a shellfish belonging to the mussel family, is one of the important edible bivalves attached to the coastal reef areas using a byssus of highly adhesive proteinaceous fiber bundles. M. edulis is native to Europe and the Mediterranean, but is currently farmed in coastal areas of Korea, and is mainly used as a minor ingredient for soup or boiled foods. Due to its high protein content, M. edulis are effective in preventing coronary heart disease (CHD) and hypertension disease, and the amino acid composition of the protein contains glutamic acid and glycine, including a high content of taurine, which regulates the liver’s function and causes of Alzheimer's disease. In addition, although the lipid content is relatively low, it is generally well known that it is effective for antioxidant capacity, arthritis, and inflammation by high content of astaxanthin and ω-3 fatty acids. For this reason, it is believed that M. edulis have high potential for commercial development of functional foods or dietary supplements. Recently, there is an increasing number in the feasibility studies of new emerging green technologies since the conventional extraction techniques use a high amount of toxic solvents which compromise the safety of extracts, requiring extra-purification steps for their removal to avoid health risks they may cause upon ingestion. Therefore, in this study, supercritical carbon dioxide (SC-CO2) and subcritical water hydrolysis (SWH) process, which are eco-friendly technologies, were applied to extract physiological active substances. Carbon dioxide (CO2), which is widely used as a supercritical fluid, has characteristics of relatively low critical temperature (31.10°C) and pressure (7.39 MPa) compared to other fluids, and is widely used for separation and purification of heat-sensitive natural materials. In addition, CO2 is colorless, non-toxic, and non-flammable, so there is no residual solvent after extraction and can be reused. Since the extract is easy to separate from the solvent, it has high selectivity with excellent sample recovery. The extraction conditions conducted for SC-CO2 varied for pressure (20, 30 MPa) and temperature (45, 55℃), while the flow rate was kept constant during the experiment (27 g/min). The extracted M. edulis oil analyzed the extraction yield, oil stability (acid value and peroxide value), fatty acid composition, antioxidant activity (DPPH and ABTS), color and TGA. The lipid-free residue extracted by supercritical carbon dioxide was hydrolyzed through a subcritical water hydrolysis process. Subcritical water is one of the chemical reactions generated due to changes in physical properties including dielectric constant depending on temperature or pressure. These properties result in a hydrolysis reaction capable of decomposing peptide bonds, ester bonds and glycosidic bonds without a catalyst. SWH was used for the purpose of enhancing the food functionality and improve yield as well as safety, economics and environmental friendliness. Applied temperatures ranged from 120 to 240°C with the pressure and reaction time fixed at 30 bar and 30 min, respectively. The obtained M. edulis hydrolysates measured hydrolysis efficiency, pH, color, antioxidant capacity (ABTS, DPPH and FRAP), total phenolic content (TPC), total flavonoid content (TFC), total protein, amino acid composition, taurine content and anti-hypertensive activity. As a results, the best extraction yield condition of M. edulis oil extracted by SC-CO2 indicated at 55℃/30 MPa, resulting in the highest yield of 6.02±0.79%. The best conditions of oil stability and antioxidant capacity of M. edulis oil was obtained at 55℃/30 MPa and 45℃/20 MPa, respectively. The oils were characterized for their fatty acid (FAs) composition using gas chromatography, while it was revealed that the major FAs were Palmitic acid, Palmitoleic acid, Electroosapentaenoic acid (EPA), and Docosahexaenoic acid (DHA). Astaxanthin content increased with increasing extraction pressure, it showed the highest content at 45℃/30 MPa with 9.88±0.33 mg ASX/g oil. In addition, the hydrolysis efficiency of M. edulis hydrolysates increased continuously with increasing temperature, showed the highest value of 90.65±0.11% at 240°C. DPPH, ABTS, FRAP, TFC also indicated maximum activity at 240°C with 12.79±0.01 mg TE/g dried sample, 9.52±0.02 mg TE/g dried sample, 4.68±0.08 mg TE/g dried sample, 15.66±0.06 mg QE/g dried sample, respectively, while TPC showed the higest content at 210°C with 7.18±0.20 mg GAE/g dried sample. The total protein content and anti-hypertensive activity reached the highest values at 180°C with 52.87±0.16 g BSA/100 g dried sample and 95.38±0.20%, respectively. From the obtained results, M. edulis extracts recovered using SC-CO2 and SWH is a effective techniques for producing physiological substances and will have important influence in food industry, and is considered to be highly utilized as basic data for use as a material that can be used in various fields.