Determination of quality of fish fillets coated with transglutaminase enzyme

In this study, the effect of spraying microbial transglutaminase (MTGase) at various levels on the quality of mackerel fillets was investigated. Mackerel (Scomber scombrus, Linnaeus, 1758) species were used as a research material. The surfaces of the filleted fish were coated with enzyme solution (1, 4, 7 and 10 units MTGase) and the samples without enzyme were regarded as control group. Fillets are placed into the foam plates and stored at 4±2°C. pH value, total volatile basic nitrogen (TVB-N), totox value, microbial growth (TMAB, TPAB, yeast and mould, coliform bacteria), sensory changes (odour, texture, appearance), colour values (L*, a*, b*) of mackerel samples were analyzed on 2 day intervals during refrigerated storage. The increase in pH values was similar with TVB-N increment due to accumulation of basic compounds. The increase in the MTGase concentration suppressed the rise in pH values. The treatment with 7 unit MTGase was affective in hindering the formation of TVB-N compounds. Control treatments had highest values than samples treated with MTGase at the end of the storage. As a result of totox value, which gives information about lipid oxidation level by considering primary and secondary oxidation products, the increase in MTGase concentration had positive effect on hindering the formation of lipid oxidation. More successful results were obtained with enzyme treated samples comparing to control fillets. The increase in microbiological growth was suppressed with the transglutaminase enzyme spraying to the fillets of mackerel. The best results were obtained with the addition of transglutaminase enzyme in the concentration of 7 unit MTGase in terms of the inhibition of TMAB, TPAB, coliform bacteria and yeast and molds. The most suitable samples for the growth of microorganisms were control samples and the samples treated with 1 unit MTGase. Biochemical composition of fish and the concentration of enzyme influenced the refraction of light. Lowest L* values were determined in T10 samples, whereas control samples had the highest values. The difference between the treatments was significant (p<0.01) in a* and b* values. The highest a* scores were determined in T10 samples, meanwhile the highest scores for b* was determined in T7 samples. Panelists, who were chosen from Akdeniz University Faculty of Fisheries for sensory analyses, preferred the samples treated with 7 unit MTGase in terms of odour, texture and appearance evaluations. Considering to all parameters, it can be said that T7 samples were more affective in keeping the quality of mackerel fillets comparing to other MTGase treatments and control samples. It is important to use the correct concentration regarding of the increasing MTGase. KEY WORDS: Mackerel, Transglutaminase, Quality changes, Shelf-life