Enzymatic Preparation And Deodorization Of Large Yellow Croaker Liver Oil

The large yellow croaker(Pseudosciaena crocea)is an important economic fish in the coastal waters of China.It is mainly distributed in the Chinese mainland near the east of Qiongzhou Strait and the west coast of the Yellow Sea.With the increasing production of the large yellow croaker(Pseudosciaena crocea),the yield of its byproducts is higher and higher.If these by-products are not used effectively,it will not only pollute the environment,but also waste resources seriously.The liver of the large yellow croaker(Pseudosciaena crocea)contains a large amount of lipid and protein,and the liver of the large yellow croaker(Pseudosciaena crocea)is a large proportion of its viscera,which has more development potential.Therefore,in order to maximize the utilization of large yellow croaker liver,the nutritional composition of large yellow croaker liver was analyzed,and the optimal process of enzymatic extraction of large yellow croaker liver oil was explored.Meanwhile,the influence of deodorization refining method on volatile components and fatty acids of large yellow croaker liver oil was also studied.The main research contents and results are as followsPart 1: analysis and evaluation of nutritional components in the liver of the large yellow croaker(Pseudosciaena crocea)The nutritional components of the liver of the large yellow croaker were analyzed and evaluated in detail in order to provide basis for the development of nutritional and functional products.The results showed that the content of water,protein and fat in liver was 45.71%,8.25% and 37.97%,respectively.The liver of large yellow croaker is rich in amino acids,and the determination results of fatty acids are also ideal.The content of unsaturated fatty acids is up to 62.63%,in which EPA and DHA account for9.42%.At the same time,the liver of large yellow croaker is also rich in phospholipids,vitamins and trace elements.The contents of heavy metals(such as Hg,as,CD,etc.)were lower than the limit of heavy metals in Chinese fish.The key components of fish liver flavor were aldehydes,ketones and alcohols.Part 2: optimization of extraction process and quality analysis of the large yellow croaker liver oilUsing the liver of large yellow croaker as raw material,the best protease was selected to extract the liver oil of the large yellow croaker.Taking the extraction rate as the evaluation index,the enzymatic hydrolysis conditions were optimized,and its quality and fatty acid composition were analyzed.The results showed that the optimum enzymolysis conditions were as follows: neutral protease 2.5%,solid-liquid ratio 1:2(g/ml),p H 7.3,enzymolysis time 4 h,enzymolysis temperature 50.3 ℃.The results showed that the extraction rate was 78.39%,the quality was better than that of light alkali method,the oil was clear,the acid value was(5.83 ± 0.15)mg/g,the iodine value was(142.65 ± 0.22)mg / 100 g,it contained 13 kinds of fatty acids(5 kinds more than that of light alkali method),and there were 8 kinds of unsaturated fatty acids,among which the content of saturated fatty acid was 19.71 g/100 g,and the content of monounsaturated fatty acid was 62.63 g/100 g.The extraction rate,quality and fatty acid composition of liver oil from large yellow croaker by enzymatic method were better than those by light alkali method.Part 3: Effect of three removal process on quality of large yellow croaker liver oilIn order to develop high quality large yellow croaker liver oil,the quality change of large yellow croaker liver oil during refining process was explored.The physical and chemical properties,fatty acids,IA,IT and volatile flavor components of fish liver oil in different stages were analyzed.The results showed that the acid value of large yellow croaker liver oil decreased by 60.42%,iodine value increased by 1.13 times,peroxide value decreased by 48.03%,and its physical and chemical properties were significantly improved.The relative content of fatty acids increased by 1.14 times,1.28 times and 1.33 times,respectively,and the IA and it values were relatively low,which did little harm to human health.Crude fish liver oil has heavy oil,fishy and sour flavor.Refining can improve its flavor.Degumming can remove the sol impurities in fish liver oil,deacidification can mainly reduce the acid value of fish liver oil,decolorization can significantly improve the color of fish liver oil from reddish brown to light yellow,and decolorization process can also slightly improve the flavor of fish liver oil.Part 4: Effect of different deodorization methods on the quality of Refined large yellow croaker liver oilAs large yellow croaker liver oil has a special fishy smell,in order to effectively remove this bad smell,the decolorized large yellow croaker liver oil was treated by different deodorization methods(rotary distillation,solid phase adsorption,deodorizer,green tea polyphenols).The physicochemical properties,fatty acids,IA,IT and volatile flavor components of the refined large yellow croaker liver oil were analyzed.The results showed that the deodorization process could significantly reduce the oil smell,fishy smell and sour taste.In the comparison of different deodorization methods,the acid value of fish liver oil could reach the lowest 0.24 ± 0.07 mg KOH/g by deodorizing liquid,while the oxidation value of fish liver oil could be effectively reduced by green tea polyphenols(GTP)(1.56 ± 0.19 mmol/kg).Because of its antioxidant activity,GTP can not only inhibit the oxidation of fish liver oil,but also keep its IA and IT values at a low level,which can reduce the probability of hyperlipidemia,coronary heart disease and other cardiovascular diseases.The composition and content of fatty acids are slightly different,but the overall quality is better,which can ensure its nutritional composition and functional characteristics.The overall effect is better.Compared with decolorized fish liver oil,the quality of deodorized fish liver oil has also been significantly improved.This study provides a theoretical basis for the development of large yellow croaker liver and the production technology of fish liver oil with high unsaturated fatty acids and good flavor quality.