Studies On The Properties And Application Of Silver Carp Enzymatic Hydrolysates

Production of freshwater fish in China ranked first in the world in 2012,freshwater fish production reached 23.3411 million tons.Due to the heavy smell of soil,freshwater fish muscle,protein freeze denaturation in processing and other causes,leading to China's freshwater fish freshness,low processing rates.Silver carp is one of China's four major fish with low price and large output(2012,3.6878 million tons).Currently on the market still dominated by fresh because of the low rate of freshwater fish processing(under 15%),the rate of corruption is 30%,resulting in an enormous waste of resources.Therefore,processing of freshwater fish such as carp and studies on the application to reduce the waste of resources,enhance the economic value of freshwater fish is of great significance.Nutritional value of this product from enzymatic hydrolysis of silver carp,purification and the antioxidant properties of hydrolysates and application in frozen surimi was studied.The powder which using isopropyl by second extraction obtained moisture content for 3.16%,protein content for 91.54%,fat content for 0.55%,and the color of powder is light yellow.The silver carp protein is hydrolyzed by composite protease and alkaline proteinase.Through the automatic amino acid analyzer analysis of their amino acid content,total content of amino acid in fish flour is 905.9 mg/g,the content of 7 kinds essential amino acids is 400.9 mg/g in protein.It has exceeded the World Health Organization recommended 350 mg/g of protein and other amino acids in total reach to the recommended values.The seven kinds of essential amino acid conten in composite hydrolysates and alkaline hydrolysates are higher than the concent in eggs.De-fat powder's amino acid nitrogen is only 0.58%,but alkaline hydrolysate' and compound hydrolysate'amino acid nitrogen are 2.29 times and 3.98 times than that in de-fat powder respectively.AAS and IPC-MS measurement results shows arsenic,lead and mercury pollutants in de-fat powder and hydrolysates did not exceed the standard limit.HPLC result shows the two hydrolysates' eluting peaks mainly focused on retention time periods for 9 min?14 min,corresponding to molecular weight 700?3000 Da.Sephadex G-50 to purify the 30min hydrolysates of composite protease and alkaline protease.The best purification conditions are:composite protease hydrolysates in concentration 20mg/mL,ultra pure water wash off,sample volume 15mL,wash off rate 1mL/min,225nm wavelength detection;alkaline protease hydrolysates in concentration 20mg/mL,and ultra pure water to wash off,volume 9mL on,elution rate 1mL/min,225nm wavelength detection.The alkaline hydrolysates second elution peak's total antioxidant capacity and inhibition of hydroxyl radicals are stronger and composite hydrolysates eluting peaks' resistance to superoxide anion capacity are stronger than the alkaline hydrolysate's.HPLC analysis the three wash off peak finding its molecular volume respectively for:composite protease and alkaline protease hydrolysates product's wash off peak range for 1000?1500Da.The first peak of alkaline protease solutions 30min product ranges for 300?700Da,the second wash off peak of alkaline protease solutions 30min product and composite protease product molecular volume range in 1 000?1500Da,which may have better anti-oxidation properties.Studied the effect on the quality of frozen surimi by 30min complex enzymatic hydrolysis product and 30min alkaline enzymatic hydrolysis product,and compared to the effect by sucrose-sorbitol.Results are displayed that after 4 weeks frozen,2%composite hydrolysates adding group and sucrose-sorbitol group 's gel strength and hardness are raised,other three samples are similar to 0 week's.As the frozen days change,elasticity of the 5 samples were slightly lower,partly reflecting surimi's quality change.In addition,under the condition of frozen,all samples' color are less affected.Scan electric mirror results displayed 5 samples are appeared fish protein gathered phenomenon,and 2%composite enzyme solutions product added group and sucrose-sorbic added group's molecular gathered phenomenon are lighter.Indicates that though has added commercial anti-frozen agent and enzyme solutions product,the quality of surimi still will decresed,but 2%of composite protease solutions product and sucrose-sorbic can delay the bad effect on surimi's quality in frozen.