Electron spin resonance (ESR) study on free radical transfer in fish lipid-protein interaction

✍ Scribed by Saeed, Suhur; Fawthrop, Susan A; Howell, Nazlin K

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 142 KB
• Volume: 79
• Category: Article
• ISSN: 0022-5142
• DOI: 10.1002/(sici)1097-0010(199910)79:13<1809::aid-jsfa440>3.0.co;2-v

✦ Synopsis

Oxidised lipids interact with proteins causing undersirable changes in the nutritional and functional properties, including a loss of amino acids, cross-linking and damage to proteins and DNA. Proteins including egg lysozyme, egg ovalbumin, ®sh myosin and amino acids arginine, lysine and histidine were exposed to oxidised lipids methyl linoleate and oil extracted from Atlantic mackerel (Scomber scombrus). A strong central singlet signal was induced in the proteins and amino acids which was detected by ESR spectroscopy and assigned to the carbon radical (g value range 2.0021± 2.0049); with ovalbumin and ®sh myosin a down®eld shoulder, attributed to the sulphydryl group (g value 2.014±2.017), was also observed. The above changes in the proteins were accompanied by an increase in ¯uorescence indicating the formation of cross-links. Synthetic antioxidants such as butyl hydroxytoluene (BHT) and butyl hydroxyanisole (BHA) as well as natural antioxidants ascorbic acid and a-tocopherol inhibited the development of both the free radical signal and ¯uorescence when added to the proteins prior to incubation with oxidised lipids; the central singlet signal attributed to the carbon radical was reduced by 10±50%. This paper clearly indicates direct free radical transfer from oxidised lipids to amino acids and proteins which results in protein denaturation and the formation of insoluble aggregates in ®sh ¯esh on storage.