Study On The Preparation Of Rapeseed Protein And Its Effect On The Gelation Of Silver Carp Surimi

Rapeseed protein is of high nutritive value,and its amino acid composition is sound and reasonable.Rapeseed protein has many favorable functional properties,such as the water-holding and oil-adsorbing capacity,foaming property,emulsifying property,and so on,but it has not been made the most at all.Improving the extraction ratio of rapeseed protein is of great importance on the reduction of produce costing and the increase of economic benefit.Besides,if the rapeseed protein can be added into the surimi acting as a new type additive,it is possible to not only change the residual rapeseed meal into the useful resource,which can realize the effective utilization of the excellent resource,but also develop a new kind of surimi food to diversify the surimi food variety.Firstly,this thesis makes analysis on the rapeseed meal,adopts the alkali-solution method to extract the rapeseed protein,uses the acid-isolation method to precipitate the rapeseed protein,and optimizes the corresponding technology.Secondly,this thesis researches the influence of pH value on the functional properties of rapeseed protein.Thirdly,this thesis investigates the influence of the addictive amount of rapeseed protein on the color,water-holding capacity,texture properties,puncture property,gel strength and rheological properties of silver carp surimi,and via the chemical acting force,SDS-PAGE and microstructure,the acting mechanism of the influence of rapeseed protein on the surimi gel properties.Finally,on the condition of the optimal addictive amount of rapeseed protein,this thesis researches the impact of the number of freezing-thawing circulation on the surimi gel properties.The relative results and conclusions are as follows:(1).The research analyzes the composition of the rapeseed meal.The experiment results are in the following: in the rapeseed meal,the content ratio of crude protein is45.54%,and thereinto,the content ratios of the albumin,globulin,prolamin and glutelin are 33.76%,26.22%,5.04% and 20.59% of the crude protein,respectively.The contents of phytic acid,tannin and glucosinolate are 2.62%,0.92% and 39.75umol/g,respectively.The rapeseed protein is obtained by the alkali-solution and acid-isolation method,and the optimal extraction condition determined by the orthogonal experiment,expressed as:p=11,the extraction temperature of 50?,the liquor-to-material ratio of 20 m L/g,and theextraction time of 100 min.Under this above condition,the extraction ratio can be reached to 90.98% and pI=5.The solubility of rapeseed protein presents the change trend of first reduction and later increase as the rise of pH,and it reaches to the minimum at pH=5 with the value of 6.28%.The change trend of the water-holding capacity is the same with that of the solubility,and also,the water-holding capacity reaches to the minimum at pH=5with the value of 1.16g/g.The emulsifying properties present the change trend of first reduction and later increase as the rise of pH,and it is the worst at the isoelectric point.When the pH varies from 5 to 8,the foaming ability of rapeseed protein is relatively weak,and the foaming stability is the best at pI.When the pH varies between 6.5 and 11.0,the foaming stability increases as the rise of pH.(2).The rapeseed protein is obtained under the optimal extraction technology condition,and the thesis researches the influence of the addictive amount(0,0.5%,1%,1.5% and 2%)of rapeseed protein on the quality of the surimi.After the add of the rapeseed protein,the water-holding capacity,breaking force,hardness and storage modulus(G')present the change trend of first increase and later reduction as the rise of the rapeseed protein addictive,and all reach to the maximum values at 1.5%.Besides,the relative indexes of the experimental group are all higher than the corresponding blank group.As the continuous rise of the addictive,the values of L* and whiteness W reduce gradually,the values of a* and b* increase gradually,and the elasticity and breaking distance lower gradually.The research result of chemical acting force indicates that the rapeseed protein improves the gel properties of silver carp surimi by forming the disulfide bond and hydrogen bond.The research result of SDS-PAGE and microstructure show that the rapeseed protein may act as a kind of inactive physical filler and does not improve the gel properties of surimi by crosslinking with surimi protein.Combining with all above factors,it can conclude that adding 1.5% rapeseed protein is able to improve the gel properties of surimi ideally.(3).Under the condition of the freezing and thawing cycle,this thesis researches the influence of rapeseed protein on the TBA value,volatile basic nitrogen,color,water-holding capacity,TPA index and gel strength of the silver carp surimi.The experiment result shows that in the process of the freezing-thawing cycle,the TBA value,volatile basic nitrogen,a* value and b* value increase as the increasing number of the freezing-thawing cycle,while the L* value,W value,TPA index and gel strength reduce as the increasing number of the freezing-thawing cycle.After the addition of rapeseed protein,the water-holding capacity,TPA and gel strength of the silver carp surimi in the experimental group are all higher than the blank group.