Research On The Improvement Of Methods For Determination Of Peroxide Value In Edible Oils

Edible oils are recongnized as one of three essential nutrients in human diets,which not only provide essential fatty acid and energy for human body,but also promote the absorption of fat soluble vitamins.However,edible oils are oxidized during processing and storage such as autoxidation,decomposition,condensation,and polymerization because of inappropriate temperature,light,oxygen during storage.The initial oxidation products that accumulate in oils are hydro-peroxides,which may subsequently break down to form lower-molecular weight compounds,such as alcohols,aldehydes,free fatty acids,and ketones.These compounds for long-term intake have damage in health.Traditional methods for oil oxidation detection involve complicated procedures,large amounts of organic solvent,and are time-consuming.In this paper,calbrations of peroxide value model waswere developed and verified by using different common edible oils as experiment material basing on ultraviolet spectrophotometry,near-infrared spectroscopy,electrical conductivity.The main results are as follows:(1)To establish an ultraviolet spectrometric method for the determination of peroxide value(PV)in edible oils,PV determination calbration was developed by using edible oils as experiment material,based on the stoichiometric reaction of hydroperoxides with the triphenylphosphine(TPP)in oil to produce triphenylphosphineoxide(TPPO),which reveals a measurable absorption band at 264 nm and 266 nm,respectively.Simulating TPP and hydrogen peroxide reacts TPPO reactions,different peroxide value sample and common edible oils were taken to validate this model.The proposed method was correlated with national standard method,proving that there is no significant difference in the results.Therefore,developed method could serve as an alternative to the tradition method,for the determination of PV in edible oils.(2)Basing on the stoichiometric reaction of hydroperoxides with the triphenylphosphine(TPP)in oil to produce triphenylphosphineoxide(TPPO),Near-infrared transmission spectroscopy was used for rapid determination of peroxide value of edible oils.The quantitative calbration was developed in range of 4650～4500cm-1 by partial least squares(PLS).Different peroxide value sample and common edible oils were taken to validate it,the result indicated that rapid detection of peroxide value in edible oils with NIR was feasible compared with national standard method.(3)The electrical conductivity method for determination of peroxide value in edible oils was developed based on electrical conductivity change value of aqueous phase during reaction.PV determination model was established by using rapeseed oil as experiment material,improving of national standard method.Different peroxide value samples and common edible oils were taken to validate this model by comparison and analysis of PV determined by the conductivity method and iodimetry.The proposed method was correlated with national standard method,there is no significant difference in the results for different type oils.(4)The accuracy and maneuverability of ultraviolet spectrophotometry,near-infrared spectroscopy,electrical conductivity method for determination of peroxide value were compared according to the analysis of required equipment,sample weight,The reagents used and security,convenience for operation,the accuracy.The results showed practical applications should be comprehensive consideration to choose the suitable method.