How does Raman spectroscopy identify edible oil?

What are the pain points of traditional chemical analysis?

The quality of edible vegetable oil, adulteration detection and quantitative analysis of key physical and chemical indicators of fats and oils are research hotspots in the field of food testing. Traditional chemical analysis methods have limitations such as complicated operations, costing the same time, and polluting the environment. There is an urgent need for a fast and accurate method.
Testing means to determine its quality.

What are the application areas of Raman spectroscopy?

Raman spectroscopy, as a spectroscopic detection method that has received widespread attention in recent years, has been successfully used in petrochemical, medical, pharmaceutical, archaeological identification, food safety, environmental protection and other fields.

Advantages of Raman spectroscopy

Raman spectroscopy is a rapid detection method that has developed vigorously in recent years. It has the advantages of fast, efficient, pollution-free, no pre-processing, and non-destructive analysis. It has been widely used in many fields! Compared with near-infrared spectroscopy, Raman
The spectral peaks are clear and sharp, rich in information, and have a certain physical meaning. They are usually the characteristic frequency bands of each component to be measured in the Raman spectrum. The components can be analyzed by the characteristic Raman peaks of the sample.

How to use Raman spectroscopy to analyze edible vegetable oil?

The Raman spectrum information of edible vegetable oils is very rich. The "one C one C one" in the oil structure has a greater contribution to the molecular vibration in the Raman spectrum. The main difference of fatty acids in different types of vegetable oils is their quantitative changes.

Raman spectroscopy is used to analyze the quality and physical and chemical properties of edible vegetable oil, and a rapid analysis method for the identification of edible vegetable oil varieties is proposed.

Experimental research

Vegetable oil samples were purchased from supermarkets and grain and oil wholesale markets, including 12 samples of soybean oil, 8 samples of palm oil, 5 samples of canola oil, 5 samples of olive oil, 5 samples of corn oil, 4 samples of camellia oil and 4 samples of peanut oil.

The Raman spectral measurement system was used to measure 43 samples of edible vegetable oil. Austro-tiancheng Raman spectrometer was used for the spectrometer. The central wavelength of the laser was 785nm, the measured room temperature was 200C, and the spectrometer integral time was 5s.

Figure 1. Raw Raman spectrum of vegetable oil

It can be seen from the original spectrum that the characteristic peaks of the Raman signal of edible oil are more prominent, but at the same time, due to the interference of noise and fluorescence, the original spectrum has a baseline drift, and there are some interferences in the signal.
The Raman spectrum is preprocessed. The figure below is the preprocessed spectrum of vegetable oil Raman spectrum.

(A) Spectrum after baseline correction (B) Spectrum after normalization

Conclusion

A rapid identification method for edible vegetable oil based on Raman spectrum. Based on the use of known edible vegetable oil samples to construct a training sample database, automatic type identification is performed on samples of unknown edible vegetable oil varieties. The experimental results show that using the two-point method of edible oil unsaturation for feature extraction, the clustering effect of each category of samples is better, and the class spacing is larger.

The rapid identification method of edible vegetable oil based on Raman spectroscopy can accurately realize the classification of pure edible vegetable oil varieties, which lays the foundation for the follow-up research on the adulteration of edible vegetable oil.