Isolation of a natural antioxidant from shrimp waste

Abstract

Shrimp waste samples were extracted with a variety of organic solvents. Each fraction was measured for antioxidant activity by determining the rate of oxidation of β-carotene-linoleic acid in an emulsion system. An ethanol extract exhibited the highest antioxidant activity. Purification of the most active fraction was accomplished by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Antioxidant activity was not significantly effected by heating at 100°C for 4 hr or 30 days storage at 4°C. Purified antioxidant samples were further analyzed by several spectroscopy methods such as Fourier transformed-infrared spectroscopy (FT-IR), mass spectrometry and nuclear magnetic resonance (NMR). The antioxidant was characterized as an ortho-disubstituted benzene. The content of antioxidant in shrimp waste was estimated to be 1.80 ppm. Antioxidant from shrimp waste was extracted and partially purified by silica gel glass column chromatography. Two species of rockfish (Sebastolobus alascanus, Sebastes ruberriumus) were treated with crude antioxidant solution respectively, while rockfish fillets (Sebastes alutus) were treated with different concentrations of antioxidant solutions from the column chromatography. Higher a* values were found in rockfish samples treated with antioxidants compared to the control without antioxidant during iced storage. Furthermore, rockfish fillets treated with 0.20%, and 0.50% (w/v) antioxidant had lower 2-thiobarbituric acid (TBA) values compared to the control group of rockfish fillets (Sebastes alutus). Crude extract (0.50% w/w), and purified antioxidant (0.10%, 0.20%, and 0.50% w/w) from shrimp waste were applied to sablefish mince and evaluated for their effectiveness to inhibit oxidative and hydrolytic rancidity of mince samples. Treatments with crude extract (0.5%), partially purified antioxidant (0.2%, 0.5%) had a significantly lower TBA, and peroxide value (PV) compared to the control group during refrigerated (4°C) and frozen storage (-20°C). The results from free fatty acid values suggested that antioxidant from shrimp waste had no effect on hydrolytic rancidity in sablefish mince.