Effect Of Fish Skin On Gel Strength And Structure Of Surimi Gels

Fish skin is the main by-product in the processing of aquatic products.In order to improve the utilization ratio of fish skin,the possibility of adding fish skin to surimi products was analyzed.The effects of fish skin addition ratio on the gel properties and protein structure of Alaska pollock surimi were investigated,the correlativity of surimi gel parameters after adding fish skin was dissected.The main results are as follows:(1)A light gray colored dermis was prepared from haddock skin for addition to surimi under the following processing conditions: soaking in 0.001 mol/L acetic acid solution for 3 h to remove impurities such as fish scales and epidermis to obtain the dermis.Then,immersing in0.05 mol/L acetic acid solution for 3 h and crushed into mud.After crushing into a puree,it was added to surimi by 0,5,10,15,and 20% and mixed evenly as surimi with added skin.(2)The gel properties were characterized by gel strength,texture,water holding capacity,whiteness and pH.It was found that the gel strength,texture,water holding capacity and whiteness of surimi gels decreased with the addition of fish skin.When the fish skin addition ratio was 5%,the gel strength,springiness and water holding capacity of surimi gel did not decrease significantly(P>0.05),while the hardness decreased significantly(P<0.05).Therefore,the fish skin addition ratio should be less than 5%.The addition of Transglutaminase(TGase)improved the gel properties of surimi gels,and had little effect on whiteness.(3)The effects of haddock skin on gel intermolecular force,protein structure,thermal stability,protein molecular composition and microstructure of surimi gels were investigated by using Fourier transform infrared spectroscopy,Differential scanning calorimeter,Scanning electron microscope and Sodium lauryl sulfate polyacrylamide gel electrophoresis.The data showed that the addition of fish skin and TGase had little effect on the solubility of hydrogen bonds and protein structure.Hydrophobic interactions and disulfide bonds decreased with the increase of the fish skin addition ratio,while hydrophobic interactions and disulfide bonds increased when TGase was added.The first and third thermal denaturation temperatures of surimi decreased with increasing fish skin addition ratio,while the second thermal denaturation temperature did not change significantly(P>0.05).Fish skin hindered the cross-linking between myosin heavy chains in surimi gels,resulting in a loose and porous gel network structure.The addition of TGase then promoted the cross-linking of myosin heavy chains to form a more dense gel structure.(4)The gel samples of 5 different additives were prepared.The gel strength,sensory evaluation and folding test were measured separately,and then correlation analysis was performed between each index.The results showed that mixed gel with the addition of fish skin was fragile after folding and had great effect on sensory score,while the addition of TGase improved the folding effect.mixed gel with the addition of fish skin,and the addition of fish skin had a greater effect on the sensory score of surimi gels.After correlation analysis,it was obtained that tissue status was highly significantly and positively correlated with color and sensory scores(P<0.01);sensory scores showed a highly significant positive correlation with color(P<0.01);gel strength showed a significant positive correlation with folding test(P<0.05).According to the above results,we should pay attention to the effect of fish skin on gel properties and control the addition ratio of fish skin in surimi.