Study On Gel Characterization Of Tilapia Myofibrillar Protein Affected By Konjac Glucomannan And Fattiness

Surimi sea food is aquatic high protein food based on fish as raw material, and through a series of processing. Because of its delicious, nutritious and convenient characteristic, the consumption of surimi sea food is increasing rapidly. Myofibrillar protein is a major component of surimi to form an elastic gel, the surimi gel properties are directly related to the structure and the nature of it. However, it is still lack of comprehensive and deep awareness about the myofibrillar protein complex gel formation mechnism currently. The intermolecular interactions beween polysaccharides and proteins and superamolecular structure in composite gel is the bonc linked gel properties and gel mechanism. It can provide theoretical foundation and guidence to develop new products through studying polysaccharide-protein supramolecular structure and gel mechanism.In this study, we acquired different molecular weights Konjac glucomannan(KGM) through radiating the KGM with different radiation dose. Then, adding the different molecular weights KGM into myofibrillar system, resulting the myofibrillar-KGM composite gel. By measuring the composite gel gel strength, water holding capacity, gel whiteness, rheology, microstructure and other parameters, we can explore the influence mechanism of different molecular weight KGM on myofibrillar protein gel properties. The dynamic rheology results show that from the rheological dynamic curve of the overall trend we can see that between 20℃ and 40℃, the storage modulus of the composite gel system showing a steady upward trend, and between 40℃ and 50℃, the gel system storage modulus decreased rapidly, when the temperature over 50℃, the composite gel system rapidly rises to a certain level, and then maintence a steady state. When the adding amount of KGM is the same, the composite gel with adding of KGM of 53 k Da molecular weight showed a relatively high storage modulus. However, the storage modulus of composite gel with KGM of 923.8k Da molecular weight was significantly higher than other groups before 40℃. The textural result showed that 307.8k Da,169.0k Da,53.0k Da KGM can significantly improved the strength of the composite gels in 95℃, improving 2%~4.6%. The composite gels heated-induced had a higher whiteness. 923.8k Da,307.8k Da,169.0k Da KGM were beneficial to the water-holding capacity of composite gels in 95℃, improving 7%~29%. Scanning electron microscopic show that with the decreasing of KGM Molecular Weight,the pore of composite gels decreased. It’s not conducive to increase the composite gels strength when the pore of composite gels too big or too small.It can be concluded that medium molecular weight KGM is more beneficial to increase the strength and improve the water holding capacity.Next, in this experiment the pre-emulsified corn oil and lard were added to myofibrillar protein system, and studyed the mechanism of emulsified oil on composite gel gel strength, gel whiteness, water content, the microstructure and other aspects. Rheological results showed that: with the adding amount increase of emulsified oil into myofibrillar protein system, the composite gel storage modulus scales upward trend emerged. Corn oil-myofibrillar protein composite gel storage modulus was significantly higher than the control group storage modulus, but significantly lower than the emulsified lard- myofibrillar protein composite gel storage modulus. It was found that when oil dosage was 1% or 2%, the gel strength of corn oil-myofibrillar protein composite gel was significant(p<0.05) lower than lard-myofibrillar protein composite gel, but still significant(p<0.05) higher than the control group. It was also can be concluded that the gel water holding capacity, gel whiteness also significantly higher than the control group. Microstructure observation demonstrated that there were many voids in the three-dimensional structure of myofibrillar protein gels without the adding of emulsified oil and the pore was significantly reduced with the adding of emulsified oil, indicating that part of the emulsified oil particles filled in the spatial structure of the protein. This result coincided with that composite gel with the adding of fat can can increase the gel strength, water holding capacity. The experimental results showed that, it was possible that lard can be instead of corn oil in surimi products processing production process.This results have a certain theoretical significance in improving the quality of surimi sea food and the adding of KGM and oil in surimi products. Meanwhile preliminary elaborated the impact mechanism of KGM and oil on myofibrillar protein gel, thus laying the theoretical foundation for the next further study.The gel strength composite gel system, water retention gel whiteness, rheology, microstructure of composite gels can be effected by different molecular KGM. Medium molecular weight KGM is benifical for the keeping of water-holding capacity and improving the gel strength. And the composite gels gel strength, gel whiteness, water-holding capacity, microstructure can also be effected by emulsified oil. It is possible that lard can be instead of corn oil in surimi products processing production process. This thesis make the foundation of further study of gel mechanism.