Determination Of Phosphatidylcholine Hydroperoxide In Cured Meat And Its Variation During Processing

This paper select phosphatidylcholine hydroperoxide(PC-OOH)as study object and the synthetic phosphatidylcholine hydroperoxide(C16:0/18:2 PC-OOH)as standard to establish the detection method of PC-OOH in cured meat products;And on this basis,the variations of PC-OOH and its contribution to lipid oxidation in the processing of dry-cured Parabramis pekinensis were explored;Finally,the influence of pH,temperature and NaCl concentration on the formation of PC-OOH in phosphatidyl choline oxidation reaction system were studied.The paper divided into three parts,the specific study contents and results were as followed:1.Determination of Phosphatidylcholine Hydroperoxide in Dry Cured Meat Products by Normal-Phase High Performance Liquid ChromatographyA high-performance liquid chromatographic(HPLC)method was established to determine phosphatidylcholine monohydroperoxide(PC-OOH)in dry cured meat products.PC-OOH in dry cured meat samples was extracted with chloroform/methanol(2:1,v/v),followed by determination by high performance liquid chromatography connected to a photo-diode array detector(HPLC-PAD)with synthetic C16:0/18:2PC-OOH as the standard.The chromatographic conditions were set as follows:column,Lichrosorb Si 60(250*4.0 mm,5 ?m);mobile phase,water and n-hexane/isopropanol(3:2,V/V)in gradient elution;flow rate,1.0 mL/min;column temperature,30?;detection wavelength,234 nm.Results showed a good linear relationship was yielded in the range of 20-600 nmol/mL(R2=0.9999),and the detection limit and the quantification limit were 5.8 nmol/mL and 19.4 nmol/mL,respectively.The recoveries of PC-OOH spiked at 32?240 nmol/g were in the range of 79.4?91.9%.The contents of PC-OOH in dry-cured fish,farm sausage A,B and Chinese ham samples were in the range of 92.40?296.99 nmol/g,while smoked meat was not detected.2.Studys of Phosphatidylcholine Hydroperoxide during Processing of Chinese Traditional Dry-cured Parabramis pekinensisDry-cured fish was processed using parabramis pekinensis as material by wet-salting and drying-ripening.In order to explore the change rule of phosphatidylcholine hydroperoxide(PC-OOH)value and the contribution of it to lipid oxidation in intramuscular lipids,the changes in physicochemical indexes,total lipid(TL),neutral lipids(NL),phospholipid(PL),free fatty acids(FFAs),TBARS,peroxide value(POV),conjugated dienes(CD),lipoxygenase(LOX)activities PC-OOH were measured during processing.Results showed that PC-OOH increased significantly during wet-salting and early dry-ripening stages followed by significant decreases until the end of process;LOX was closely correlated with daily variations of PC-OOH,indicating that LOX involved in phospholipid primary oxidation;the proportion of PC-OOH and POV from 1/2 in the begnning decreased to 1/3 in the end,indicating that the contribution of PC-OOH to POV show a downward trend,but PC-OOH has always been a major contributor to POV.3.The Influence of pH,Temperature and NaCl Concentration on the Formation of Phosphatidylcholine HydroperoxideThe effects of pH,temperature and NaCl concentration on the formation of the C16:0/18:2 PC-OOH were studied.In the range of pH 5.5-8.5,C16:0/18:2 PC-OOH value were decreased with the increase of pH in non-enzymatic oxidation system,but in enzymatic oxidation system the value increased in the lower pH followed by decreases with the increase of pH.In the range of 4?-45?,C16:0/18:2 PC-OOH value increased with the increase of temperature in non-enzymatic oxidation system;while in the enzymatic oxidation system,C16:0/18:2 PC-OOH value showed an i trend and thereafter decreased.With the increasing of salt concentration(0%-9.0%),C16:0/18:2 PC-OOH value in four systems were all showed a downward trend after the first rise.The results show that pH,temperature and NaCl concentration have a significant impact on the formation of C16:0/18:2 PC-OOH.