| As an important component of biological membrane, lecithin possesses a lot ofnutritional and health care functions, such as delaying senility, lipometabolismregulation, cardiovascular diseases prevention and brain function enhancement. Thereare other researches about its anti-inflammatory, anticancer and boosting animalreproductive ability functions. In addition, as a result of its amphipathic property,lecithin is a good natural emulsifier. Therefore, lecithin is widely applied in food,nutrition, cosmetics, pharmaceutical, animal feeds and other fields. Lecithin sourcesare numerous, most studies focus on soybean lecithin, while egg yolk lecithin contentis highest. Researches on egg yolk lecithin are lesser because of high cost ofproduction. Our country has a large number of poultry resources, so it's necessary tostudy egg yolk lecithin in-depth to improve added value of poultry products andpromote poultry industry development.This research focused on egg yolk lecithin, and main methods and conclusions areas follows:Firstly, egg yolk lecithin extraction procedure was optimized. Acetone was used todeoil first, and ethanol was used to extract lecithin. Optimized ratio of material toacetone was1:9; deoiling time was1.5h through single factor experiment. Egg yolklecithin's yield as index was detected by ultraviolet absorption spectrophotometry.Single factor experiment and L9(34) orthogonal experiment shows that optimalethanol concentration was100%, extraction time was1.5h and the ration of materialto ethanol was1:14. Significant factors were ethanol concentration and ratio ofmaterial to ethanol. Acetone residual content was observed as another index. Optimalparameters that result in minimal lecithin acetone residual were ethanol concentration100%, extraction time1.0h and the ratio of material to ethanol1;10. Significant factorwas ethanol concentration. The extracted lecithin's acetone residual meets thecriterion formulated by2010Pharmacopoeia of People's Republic of China. On thebasis of early research result, water bath heating was replaced by magnetism stirringin the course of ethanol extraction, and the lecithin yield calculated by weigh methodrised to21.61%from original17.30%. Secondly, the purity of extracted egg yolk lecithin was determined. Highperformance liquid chromatography-ultraviolet detector method was used.SHIMADZU LC-2010HPLC was equipped with AGILENT ZORBAX RX-SIL silicagel column. Detection wave was200nm. Simpler binary system of methanol andethanoic acid was used as mobile phase. Flow rate was0.5mL/min. It was relativelylow and reduced mobile phase usage. External standardization quantization was used,and the standard curve linear range was wide and it was10μg/mL~160μg/mL.Detection limit was0.590μg/mL, and quantitative limit was1.968μg/mL. Theprecision, stability and recovery result was good. The purity of extracted egg yolklecithin was62.703%.Thirdly, effect on egg yolk lecithin oxidative stability of extraction procedure andstorage conditions were investigated with peroxide value and2-thiobarbituric acidreaction substance as indexes. Extraction procedure included extraction solvent,ethanol concentration and drying way of ethanol removal, and storage conditionsincluded light and temperature. For the extraction procedure, the best extractionsolvent for egg yolk lecithin was anhydrous ethanol because of its high extractionefficiency and low oxidation degree of product. Blast drying during lecithinpreparation promoted its oxidation when the temperature was lower than45℃, anddrying temperature became the dominant factor at high temperature environment,because egg yolk lecithin's oxidation was promoted significantly when it was over45℃. For storage conditions,354nm ultraviolet light significantly promoted egg yolklecithin oxidation process. Effect of storage temperature on egg yolk lecithinoxidative process was obvious, higher temperature resulted in faster oxidation rateand deeper oxidation degree. While sealing treatment could inhibit egg yolk lecithinoxidation in a certain extent.Fourthly, through accelerated oxidation storage test, this research focused onprotection effect of four kinds of antioxidants on egg yolk lecithin's oxidation, withperoxide value as the index. The results showed that L-ascorbic acid treatment groupwasn't obviously different from the control group, while DL-alpha-tocopherolpossessed obvious protective effect, and added2mg content was better than4mg.Tertiary butylhydroquinone (TBHQ) and2,6-Di-tert-butyl-4-methylphenol (BHT)all effectively inhibited the oxidation process of egg yolk lecithin. The protectiveeffect of TBHQ wasn't distinct with different content, while higher BHT content protected egg yolk lecithin oxidation better.It is expected that the exploration about egg yolk lecithin's extraction, oxidativestability and oxidative protection could provide some reference for additionalresearches and industrialization production. |
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