Determination Methods For Qualitative Analysis Of Edible Oil Oxidation

Edible oils are highly susceptible to oxidization and decomposition because of inappropriate temperature, light and oxygen during processing and storage. In addition, 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. Therefore, the detecting technique for qualitative analysis of edible oil oxidation is particularly significant. Taken the common edible oils as raw material, peroxide values(PVs)of oils are measured according to the national standard and then established a reference set.The qualitative analysis of edible oils with different oxidation degrees are performed with the application of Fourier infrared spectrum(FTIR) technology and electronic nose(E-nose)technology, respectively, combined with Markov distance discriminating analysis, cluster analysis(CA), principal component analysis(PCA), and linear discriminant analysis(LDA).Some discussions were preceded on the kits which were used for measuring the oil oxidation.The main results are summarized as follows:(1) Taken the common edible oils as raw material, PVs of oils are measured according to the national standard(GB/T 5538-5538 / ISO 3960:2001) and then established a reference set.The qualitative analysis of edible oils with different oxidation degrees are performed with the application of FTIR technology to adjust the optical path and combining with the Markov distance discriminating analysis method. The results of model validation show that the recognition rate of the established discriminant model can reach to 100% at the wave-number range of 3750-3150 cm-1 with the application of PE-FTIR technology combined with Markov distance discriminant analysis.(2) A rapid method for identifying edible oil oxidation was established by obtaining common edible oils as raw materials. The PVs of these oils were then measured according to the national standard(GB/T 5538-5538 / ISO 3960:2001) to establish a reference set.Qualitative discrimination between oxidized and non-oxidized oils was modeled based on an E-nose system combined with CA, PCA, and LDA. Results indicated that the classification model was well built using CA, PCA, and LDA with both calibration model recognition rates100%, and the validation model recognition rates of CA, PCA, and LDA 95.8%, 98.9%, and100%, respectively. Compared with classical methods, this new approach could represent an alternative and innovative tool for rapid and low-cost qualitative analysis of edible oil oxidation.(3) To realize the fast and convenient methods of edible oil detecting, the subject chooses an index of edible oil oxidization to study. We chose PV as an index to evaluate different kinds of oils, and use national standard method to determine the PV of oils. Through the studying of organic solvents, the mix of KI and starch, and its stability, the quality of water, we optimize the conditions of oxidation detecting to ensure the requirement of the volume of Na2S2O3 when edible oil is becoming oxidized. The result indicated that when the organic solvents are adjusted to 30 ml: 10 ml and mixing KI and starch, using tap water, the detecting limit is less than 1 meq/kg. So the kit performs a positive effect in fast detecting about oil oxidization.