Objective The aim is to: obtain a detailed knowledge of the mechanisms of aggregation of proteins in frozen fish in order to allow better prediction of fish quality in terms of texture, nutrition and food safety; examine the interaction and aggregation of myofibrillar proteins from selected fish species by direct and less empirical techniques such as nuclear magnetic resonance (NMR), radiolabelling, immunocytochemistry and electron microscopy; and relate the changes in the structure and denaturation of proteins over a period of time in frozen storage to changes in physical and chemical, rheological and sensory properties.The project examined the nature of aggregation including myofibrillar protein protein, protein formaldehyde and protein lipid interactions in gadoid fish namely cod (Gadus morhua) and hake (Merluccius merluccius) in frozen storage at -20 C and -30 C.Systematic studies on cod muscle using transmission electron microscopy (TEM) showed that with whole muscle stored at -20 C the formation of aggregates appeared earlier than at -30 C and was accompanied by crosslinking, formation of microaggregates and ring shaped structures. The aggregation is suggested to be due to sodium dodecyl sulphate (SDS) soluble noncovalent covalent bonds initially and after 7 months due to covalent linkages possibly other than disulphide bonds. The Dmax value obtained from TEM morphometric studies of the deformation of the hexagonal arrangement of the myofilaments can be used to monitor changes with storage at -20 C and -30 C. Immunocytochemistry studies using electron microscopy were accomplished with polyclonal antibodies to myosin and actin.Formaldehyde interacted with a number of amino acids. The binding of myosin antibodies to myosin was reduced in the presence of formaldehyde. Hake actomyosin was affected irreversibly and to a greater degree on frozen storage and in the presence of formaldehyde than chicken actomyosin. The aggregates recovered from cod stored at higher temperatures of -10 C produced fluorescent compounds which may be associated with lipid oxidation products and which require further characterisation.Analysis of proteins by gel filtration indicated an increase in the low molecular weight proteins, initially 55 000 - 160 000 daltons followed by an increase in small molecules of less than 5000 daltons. Although the changes occurred faster in samples stored at -20 C compared with -30 C, the samples at both storage temperatures were comparable after 8 months. Clearly prolonged frozen storage leads to proteolysis. An increase in the alkali soluble protein was noted only after 5 months storage at -20 C, and increasing amounts of low molecular weight substances and myosin heavy chains were identified after 8 months. Amino acid analysis confirmed the presence of mainly myosin in the aggregates.Organoleptic changes in the stored fish at -20 C and -30 C were apparent after 158 days.Commercially important lean galoid fish are susceptible to protein denaturation and aggregation in frozen storage resulting in toughening of muscle and unpalatability. There is no satisfactory explanation for the development of aggregation as yet. It is proposed to examine in detail the nature of aggregation including myofibrillar protein, protein-formaldehyde and protein-lipid interactions in gadoid fish, namely cod (Gadus morhua) and hake (Merluccius merluccius). The studies will be undertaken on freshly caught fish and over a period of time in frozen storage at -20 C and -30 C. Systematic studies in both model systems and intact tissue will be undertaken using a powerful range of nonempirical techniques, namely tritium or carbon-13 NMR; radiolabelled TMAO to monitor the formation of formaldehyde; and immunocytochemistry combined with modern electrophoretic, chromatographic and rheological techniques to clearly define the nature of aggregation and its effect on amino acids and organoleptic properties. The research is in 4 phases: the nature of myofibrellar interactions in muscle; the distribution and quantification of formaldehyde formation in fresh and frozen fish; the changes in individual fish proteins on frozen storage; and the characterization of frozen fish proteins. Fields of science natural scienceschemical sciencesorganic chemistryaldehydesnatural sciencesbiological sciencesbiochemistrybiomoleculesproteinsnatural sciencesphysical sciencesopticsmicroscopyelectron microscopynatural sciencesbiological sciencesbiochemistrybiomoleculeslipidsnatural scienceschemical sciencesorganic chemistryamines Programme(s) FP2-FAR - Community research and coordination programmes (EEC) in the fisheries sector, 1988-1992 Topic(s) Data not available Call for proposal Data not available Funding Scheme Data not available Coordinator UNIVERSITY OF SURREY EU contribution No data Address GU2 7XH GUILDFORD United Kingdom See on map Links Website Opens in new window Total cost No data Participants (4) Sort alphabetically Sort by EU Contribution Expand all Collapse all CSIC-INST DEL FRIO Spain EU contribution No data Address C/ José Antonio Nováis, 10, Ciudad Universitaria 28040 Madrid See on map Links Website Opens in new window Total cost No data INIP-INSTITUTO NACIONAL DE INVESTIGACAO DAS PESCAS Portugal EU contribution No data Address Lisboa See on map Total cost No data Ministry of Agriculture, Fisheries and Food (MAFF) United Kingdom EU contribution No data Address 135 Abbey Road AB9 8DG Aberdeen See on map Total cost No data UNIV MADRID COMPLETENSE-CENTRO MICROSCOPIA ELECTRONICA Spain EU contribution No data Address Madrid See on map Total cost No data
