Najmeh Molaahmadibahraseman; Reza Farhoosh; Saeid Johny; Ali Sharif
Abstract
Introduction: Medical benefits of omega-3 fatty acids have led to a lot of research on fish oil. Among marine fish, Kilka has the highest industrial applications. Kilka oil contains significant amounts of omega-3 fatty acids. In the present study, oxidative stability of Kilka fish oil based on the Schaal ...
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Introduction: Medical benefits of omega-3 fatty acids have led to a lot of research on fish oil. Among marine fish, Kilka has the highest industrial applications. Kilka oil contains significant amounts of omega-3 fatty acids. In the present study, oxidative stability of Kilka fish oil based on the Schaal oven test and the use of two phenolic acid derivatives (syringic and vanillic acids) was investigated.Materials and methods: Crude Kilka fish oil was supplied by Khazar company (Babolsar, Iran). All chemicals and solvents used in this study were of analytical reagent grade and purchased from Merck (Darmstadt, Germany) and Sigma–Aldrich (St. Louis, MO). Free radical scavenging activities of phenolic compounds was measured by reading the absorbance of methanolic solutions of the antioxidants containing 1,1-diphenyl-2-picrylhdrazyl (DPPH)at 517 nm. The partition coefficient (log P) of the antioxidants was measured in terms of the maximal UV absorbance of aqueous (0.3 mM) and 50:50 aqueous/acetate buffer (0.1M, pH =5.5) solutions. In order to study the antioxidant activity in lipid systems, peroxide value of the chromatographically purified Kilka fish oil as well as its 10% oil-in-water emulsion containing 200 mg/kg of antioxidants was monitored at 55 °C. Results and discussion: Syringic acid with two methoxy groups showed higher scavenging activity (IC50) than vanillic acid with one methoxy group (54.2 vs. 418.2). Radical scavenging activity in phenolic acids had direct relationship with the type and number of electron donor groups on phenolic ring. Peroxide values changed exponentially. Despite the relatively high polarity (Log P = – 0.65) and high scavenging activity, the performance of syringic acid in Kilkafish oil was degraded as affected by inter-molecular interactions and was not in accordance with the "polar paradox" hypothesis. Antioxidant activity of syringic acid in emulsion increased significantly as compared with oil and it was similar to α-tocopherol. It was concluded that the type of emulsifier and also the way of emulsion preparation as compared with antioxidant had a more prominent role in the oxidative stability of Kilka fish oil.Introduction: Medical benefits of omega-3 fatty acids have led to a lot of research on fish oil. Among marine fish, Kilka has the highest industrial applications. Kilka oil contains significant amounts of omega-3 fatty acids. In the present study, oxidative stability of Kilka fish oil based on the Schaal oven test and the use of two phenolic acid derivatives (syringic and vanillic acids) was investigated.Materials and methods: Crude Kilka fish oil was supplied by Khazar company (Babolsar, Iran). All chemicals and solvents used in this study were of analytical reagent grade and purchased from Merck (Darmstadt, Germany) and Sigma–Aldrich (St. Louis, MO). Free radical scavenging activities of phenolic compounds was measured by reading the absorbance of methanolic solutions of the antioxidants containing 1,1-diphenyl-2-picrylhdrazyl (DPPH)at 517 nm. The partition coefficient (log P) of the antioxidants was measured in terms of the maximal UV absorbance of aqueous (0.3 mM) and 50:50 aqueous/acetate buffer (0.1M, pH =5.5) solutions. In order to study the antioxidant activity in lipid systems, peroxide value of the chromatographically purified Kilka fish oil as well as its 10% oil-in-water emulsion containing 200 mg/kg of antioxidants was monitored at 55 °C. Results and discussion: Syringic acid with two methoxy groups showed higher scavenging activity (IC50) than vanillic acid with one methoxy group (54.2 vs. 418.2). Radical scavenging activity in phenolic acids had direct relationship with the type and number of electron donor groups on phenolic ring. Peroxide values changed exponentially. Despite the relatively high polarity (Log P = – 0.65) and high scavenging activity, the performance of syringic acid in Kilkafish oil was degraded as affected by inter-molecular interactions and was not in accordance with the "polar paradox" hypothesis. Antioxidant activity of syringic acid in emulsion increased significantly as compared with oil and it was similar to α-tocopherol. It was concluded that the type of emulsifier and also the way of emulsion preparation as compared with antioxidant had a more prominent role in the oxidative stability of Kilka fish oil.
