Evaluation of lipid and protein oxidation during processing and storage of fatty fish mince
Special Symposium - Innovations in Food Technology (LMC Congress)
Innovations in Food Technology - Poster Session (LMC/Food - P1)
Keywords: oxidation, fatty fish mince
The production of mince from fatty fish species has the potential to provide high nutritional value products with appreciable level of omega 3 polyunsaturated fatty acids. Unfortunately, omega 3 fatty acids are very sensitive to oxidation. Protein fraction is also sensitive to degradation during processing and storage of fish products. Compounds formed by alteration of the lipid and protein fractions have a deleterious effect on nutritional and physico-chemical properties of the products.
The objective of the study was to evaluate oxidative reactions that take place in both lipid and protein fractions of fish mince during processing and storage of fish products, but also to identify critical factors that can lead to deleterious quality loss during storage.
Horse mackerel mince- products were produced by mimicking the washing steps in the surimi production. Three products were obtained 1) horse mackerel mince, 2) mince with intermediate fat content and 3) mince with a low fat content. These products were characterised by their qualitative and quantitative differences in their lipid and protein fractions but also by their initial level of oxidation. In order to evaluate oxidative degradations during storage, the different products were stored for up to 96 hours at +5oC and for up to 6 weeks at -10oC. Development of primary and secondary lipid oxidation products were evaluated at regular intervals during storage. Protein modifications were determined by measuring protein solubility, carbonyl groups and free thiol groups content. In order to identify if specific proteins are oxidised during processing and storage, gel electrophoresis and western immuno-blotting against protein carbonyls groups were performed.
For both storage temperatures, levels in primary and secondary lipid oxidation compounds varied most in the first part of the storage period, 24h hours for 5°C and 2 weeks for -10°C, but remained stable thereafter. During the first part of the storage period, oxidation developed differently in the different minces while the three minces showed the same oxidation pattern during prolonged storage. The samples stored at 5°C were more heavily oxidized than samples stored at -10°C. A decrease in protein solubility was also observed in the first part of the storage period for all products and for both temperatures. Free thiol contents decreased during storage of the products indicating formation of disulfide bonds, which might be responsible for protein aggregation. Protein carbonyls groups, developed during processing of the intermediate and low products to reach a maximum at T0. Per after, carbonyl content remained steady during storage at 5°C of these two products. In contrast, the mince presented low level of carbonyls at T0 but protein oxidation developed very rapidly during storage at 5°C and the carbonyl reached their maximum after 12 hours storage. Western immuno-blotting showed that high molecular weight proteins oxidized very rapidly during processing while low molecular weight proteins were not oxidized at T0. However, protein oxidation progressed during storage and low molecular weigth proteins were also oxidized in the different products after 96 hours of storage at 5°C.
Lipid and protein oxidation seemed to develop simultaneously during processing and storage of fish mince but it is necessary to investigate to which extent these reactions are linked.
Presented Wednesday 19, 13:30 to 15:00, in session Innovations in Food Technology - Poster Session (LMC/Food - P1).
