Optimization Of Detection Methods For Illegal Cooking Oil

At present, the harm of cooking oil has widly commanded whole society’s attention. In order to develop the supervision and to ensure food safety, it is very important to establish a simple, rapid, accurate and suitable detection of illegal cooking oil.This paper analyzed the different physical and chemical characteristics of cooking oil and illegal cooking oil, and a rapid detection method of illegal cooking oil was preliminarily established, the results are as follows:1. The sensory properties, moisture, peroxide value and carbonyl value, saponification value, acid value and other indicators of cooking oil, problems oil and illegal cooking oil are detected. Through the analysis and the test results, there are differences between cooking oil and illegal cooking oil in the smell, taste, peroxide value and acid value. According to these indicators, normal cooking oil and crude illegal cooking oil can be preliminarily judged2. The rapid detection and optimization of test paper of acid value. According to the literatures, micro thin layer chromatography with silica gel plate as the carrier was made. The silica gel plate can measure acid value range of illegal cooking oil in 15 seconds. Through the silica gel plate color, we can preliminary judge the oily. Only 0.1 ml sample oil on silica gel plate, acid value range are obtained after the comparison between sample oil color and standard colorimetric board. But this method only when problems oil and illegal cooking oil acid value is greater than 3.95 mg KOH/g, can be identified, what’s more, the contrast of sample color acid value with little difference is not obvious, which is easy to cause miscarriage. This study attempts to optimize color conditions, chromogenic agent, adhesive, chromogenic medium, so that we can solve the limitation of this method, but not succeed.3. The trial production of rapidly detection of peroxide value. According to the principle of oxidation reduction, test kits were made. Through the choice of chromogenic agent and chromogenic time,2 ml sample bottles as the carrier of the peroxide value kit is determined. Then with self-made methylene blue as the indicator, with the help of the needle injection, the results shows that the appropriate color for is 10 minutes.This kit achieved rapid and intuitive testing the effect of peroxide value, it can better to distinguish illegal cooking oil and normal cooking oil. This method, compared with national standard test method, is more simple, convenient, rapid and economic. Compared with the acid value, this rapid detection methods, has the characteristics of sensitive, accurate and stable color. This can applied to field and laboratory detection of illegal cooking oil, problems oilat the beginning of the rapid screening of qualitative.4. Nuclear magnetic resonance (NMR) technique for determining the content of triglycerides. By magnetic resonance imaging the correlation of the relaxation area and content of triglycerides was investigated. By using nuclear magnetic resonance (NMR) technology the content of triglyceride in different sample was detected. Next through analyzing and comparing different oil. Results showed that the size of triglyceride relaxed area was correlated with its content, the correlation equation was y=7056.4x+ 342.05, the correlation coefficient for R2=0.9997. The commercial brand sample triglyceride content of 97% or more.Crude oil pigwash triglyceride content is very low, only 61.07%. But refined cooking oil, the content of triglyceride reached 96.55%, reached the standard of normal oil, but the standard sample is below. Accordingly, normal cooking oil and crude oil has great differences in triglyceride levels, illegal cooking oil after refining triglycerides, its content can reach the standard of normal grease. The method doesn’t need solvent, nondestructive testing can be performed, compared to solid fat content measured by NMR to identify cooking oil, the easier and faster, and is less affected by temperature, but the current optimized nuclear magnetic resonance (NMR) is only applicable to crude illegal cooking oil for quick detection.