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Electron spin resonance (ESR) study on free radical transfer in fish lipid–protein interaction
Author(s) -
Saeed Suhur,
Fawthrop Susan A,
Howell Nazlin K
Publication year - 1999
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/(sici)1097-0010(199910)79:13<1809::aid-jsfa440>3.0.co;2-v
Subject(s) - chemistry , amino acid , histidine , ascorbic acid , electron paramagnetic resonance , biochemistry , lysine , radical , food science , physics , nuclear magnetic resonance
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, fish 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 fish myosin a downfield 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 fluorescence 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 α‐tocopherol inhibited the development of both the free radical signal and fluorescence 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 fish flesh on storage. © 1999 Society of Chemical Industry