Effect Of Pediococcus Pentosaceus Enzyme On Gel Properties Of Fermented Silver Carp Surimi

Fermented surimi products have broad market prospects because of its high nutritionalvalue, unique flavor, good storage and excellent security. Gel is an important characteristic offermented surimi products. So scientists focused on the study of gelation mechanism recently.Fermented surimi gel formation mechanism is complex. The effect of acid on fermentedsurimi gel has made a breakthrough. Microbes not only produced acid during thefermentation process, but also produced microbial enzymes and other substances. Because thestarter culture in fermentation is the dominant culture, the effect of its metabolites on surimigel can not be ignored. However, there is little study about the effect of microbial enzymes onsurimi gel. This paper discusses the effects of microbial enzyme on the gelproperties of fermented surimi, to provide a theoretical basis for the formation mechanism ofgelation mechanism on fermented surimi. It is practical significance on optimizing theproduction process and improving the quality of surimi.Firstly, enzyme production capacity was studied. We identified the enzyme activity indifferent pH, studied the effect of inoculation on the enzyme activity, and analyzed therelationship of time and enzyme producing. And then did the isolation and purification ofenzyme. After that, we studied the dnzymatic Properties. The results show that the extractionof the enzyme is a kind of Acidic Protease. The best fermentation time is controlled in20hours,2%inoculation quantity is better. the crude enzyme solution salted out by saturatedammonium sulfate solution with60%saturation level, separated and purified protease withDEAE-Sepharose Fast Flow anion exchange chromatography and Sephadex G-75gelfiltration chromatography. we determined the molecular weight by SDS-PAGE. And foundthe molecular weight is37KDa. Then we analyzed the properties of the protease. theoptimum temperature is35℃, remained stable at20-40℃. The optimum pH is4.0,stay relatively stability in the pH4.0-7.0. metal ions Ca2+have active effects on theprotease, Zn2+, Mg2+and Fe3+showed inhibitory effects. Inhibitors such as SDS and EDTAhave obviously inhibitory effect on the protease.Secondly， added Pediococcus pentosaceus protease to the acidified system, andmeasured the changes of non-protein nitrogen(NPN), TCA-soluble peptides and free aminoacid to research the extent of silver carp protein degradation, while measuring changes in gelstrength. The results show that the contents of NPN, TCA-soluble peptides and free aminoacid were increased，especially Glu, Leu and Ala. At the same time, gel degradation ofsurimi added protease is stronger than the blank sample.Finally, from the molecular level to further study the role of proteases in surimi geldeterioration. Added Pediococcus pentosaceus protease to silver carp actomyosin, andmeasured the changes of TCA-soluble peptides, turbidity and particle size to research theeffect of protease on silver carp actomyosin aggregation. At the same time, the structuralchanges of silver carp actomyosin were analyzed. The result shows that actomypsinaggregation is changed by protease because of the decrease on TCA-soluble peptides,turbidity and the particle size changed smaller. Besides, the secondary structure and tertiary structure of actomyosin had a certain degree of change. Circular dichroism showed a gradualincrease in-helix, it means some change happened on secondary structure. And the shift ofsecond-derivative UV spectra peaks to lower wavelengths at pH4.5. Intrinsic fluorescenceincreased after added Pediococcus pentosaceus protease.