Research On Detection Method Of Phosphatidylcholine Molecular Species In Milk Powder

Lecithin is the basis material of life, suitable for the all ages of crowd, especially children, pregnant women and the old man. Lecithin was applied to milk powder, can convenient for people to supplement lecithin, in particular, children have single diet, they were more suitable for adding lecithin through the way of milk powder. On account of lecithin as a kind of food additivein exists in food, when was spraied in milk powder, the dosage of lecithin was required between0.2%to0.3%in total dry weight of milk powder. In a general way, allow additives under0.4%. For the limits of the content of lecithin in milk powder, establish a sensitive, effective and rapid detection is great significance in guarantee food security.Nowadays, research on lecithin was main have three procedures, the first was isolated lecithin from soybeans or egg yolk, through purified, and then analyzed the content of lecithin. But most of detection can only separated which calls lecithin in the broad sense, such as phosphatidylcholine and phosphatidylethanolamines and so on, to lecithin in the narrow sense which was phosphatidylcholine, can’t require a satisfactory consequence. In fact, as a result of sn-1and sn-2of glycerin phospholipid molecules, which was esterificated by all kinds of combination of natural fatty acids, so phosphatidylcholine is generally represent the breed of molecules form.In this paper, analyzed fatty acid of phosphatidylcholine through gas chromatographic, and then make use of this way to set up a menthod to detect different kinds of phosphatidylcholine molecular, was depend on high performance liquid chromatography-mass spectrometry. Compare to two different methods of methyl, with response value as parameters, after that choose a way which suitable for phosphatidylcholine. Method of alkali catalyst was the final choice.Use mass spectrometry detector, study phosphatidylcholine repeatly, then found that different phosphatidylcholines possess same son ion clips, were184.1and125, corresponding collision voltage were respectively35v and80v. According to analyze the structure of phosphatidylcholine, can be seen that fracture of the two ion clips all in its characteristics which all phosphatidylcholine have it, if make sure this deduction, can use mass spectrometry detect each phosphatidylcholine molecules. Using C18column, analyzing through single factor experiment, finally selection was acetonitrile-methanol (5:5, v/v), elution with same gradient. Weak wash should be consistent with mobile phase, because the weak wash can enter the system, weak wash different to mobile phase will affect the experimental results. The optimize method can detect mixture of components at the same time, and qualitative and quantitative. Result of detection have a good linear, detection limit was1μg/L, the linear range was10to1000μg/L (R=0.99936), retention time of all the phosphatidylcholine less than5min.Analyze and study high performance liquid chromatography-ultraviolet examination method, using C18column for analyze. Through detection of different standard of phosphatidylcholine, found that ultraviolet detector can’t separate the two different standard of phosphatidylcholine, they have the same retention time. For the standard of mixed phosphatidylcholine also have not result which we want, and change the mobile phase can’t make any different, but the method of HPLC-UV to total content og lecithin have good effect. The result of this study obtain a suitable mobile phase is n-hexane-isopropyl alcohol-water (31/62/7, v/v/v), wavelength is205nm, detection limit is0.1mg/mL, linear range is0.5to50mg/L (R=0.9967).The paper also study method about that was extracted phosphatidylcholine from milk powder, choose lodz method and chloroform-methanol respectively to extracted fat from milk powder. Through the experiment, it is known that lodz method and chloroform-methanol(2:l, v/v) method were all suitable for extract fat from milk powder, can get same content of fat, but chloroform-methanol method is more suitable for high combined content fat of sample and high contents of phosphatide of sample, the finally selection was chloroform-methanol method. Fat of extraction was washed by acetone, so as to removing other oil and impurities which fat contains, and then extracted by ethanol, further purificated phosphatidylcholine, with methanol as dilution solvent of sample, the solution was used to test analysis. Final conclusion is that:under normal temperature, with acetone washing the fat after extraction for4times, then use40℃ethanol wash phosphatidylcholine, repeated it4times, for further purificat phosphatidylcholine.