Identification And Optical Properties Analysis Of Illegal Cooking Oil Based On Terahertz Time-domain Spectroscopy

Edible vegetable oil is an natural macromolecular compound, with fatty acid and glycerin as raw material, usually extracted from plants seeds, fruit and so on. Vegetable oil is an indispensable subsidiary foodstuff in people’s daily life, which contains a lot of beneficial materials, like minerals, fatty acid and so on. However, driven by enormous profits, some unscrupulous manufacturers obtained a lot of waste or poor-quality oil from catering trade. After simple filtration, purify, they made waste oils into cooking oil, and then re-flowing into the market. Due to the waste oils’ irrational origin, less nutrition, but also contains plenty of harmful substances, so that if we intake the waste oil for a long time that we would be get ill, even life-threatening. Faced with the severe market trend that the waste oil wanton circulation, in order to ensure that people can eat qualified edible oils, we should to strengthen the management of unscrupulous manufacturers and need to develop a testing equipment or method which can test waste oil rapidly, simply and economical.This paper adopts terahertz time-domain spectroscopy which realized that analyzed the waste oil’s optical properties and identify it quickly.Based on the terahertz frequency of biomacromolecules(such as oils and fats) in vibration and rotation, the technology of terahertz time-domain spectroscopy(THz-TDS) can detect and identify the legal and illegal cooking oils rapidly and sensitively. We have analyzed the time-domain or frequency-domain spectra and the optical parameters from three legal oils, three frying oils and one illegal cooking oil in the region of 0.3~1.6 THz. Through comparisons of the absorption coefficient and the refractive index of these spectra from these different samples, we can extract the comprehensive information about the illegal cooking oil. These results show that the THz-TDS spectroscopy can distinguish the differences between the legal and illegal cooking oil effectively, which provides a scientific and effective way to identify the illegal cooking oil.Through analysis the terahertz spectrum of three types oil,we discoveries the result that three types oil have both general and different characteristics,which provides an effective method and basis for identification of illegal cooking oil.The time delay of illegal cooking oil was significantly higher than other types of oil.The refractive index decreases with the increase of frequency,but the refractive index of illegal cooking oil was significantly higher than the regular oils and close to the frying oil.The absorption coefficient gradually increased with the increase of frequency,but the slope of absorption coefficient of illegal cooking oil was significantly higher than other types of oil. The number and position of the absorption peaks before and after frying significant changes have occurred, but the absorption peak of the illegal cooking oil is significantly different from other types of oil.