The toxicity of oil and harmful substances in oil include mycin, pesticide residues and veterinary drug residues. Mycomycin refers to a toxic substance produced by fungi. People and livestock eat food or feed containing mycomycin, which will lead to mycomycin poisoning. The source of mycomycin in oil is the infection of pathogenic fungi during the growth of oil crops. Mycomycin has strong lipophilicity and then deposits in oil products. There are also mycomycin infections during the processing, storage and transportation of oils and fats. The common mycotoxins in vegetable oil are aflatoxin, trichosporene, emetic toxin, brown aspergillin A and zearalenone. The toxic effects of pesticides are reflected in two aspects: on the one hand, pesticides can effectively eliminate and control the growth of pests and diseases; On the other hand, the use and abuse of pesticides will lead to environmental pollution and ecological imbalance, leading to pesticide residues in food and endangering human health. The main veterinary drugs used in animal husbandry production are antibiotics, hormones and parasiticides. Commonly used qualitative and quantitative analysis and detection methods mainly include gas chromatography, liquid chromatography, infrared spectroscopy, fluorescence spectroscopy, Raman spectroscopy and so on. Especially in the determination of pesticide residues, it is an effective means to connect different detectors according to the types and properties of pesticides, such as hydrogen flame ionization detector, nitrogen and phosphorus detector, electron capture detector and mass spectrometry detector.
In recent years, reports on detecting adulteration of edible oil are common. Chromatographic technology can effectively identify the adulteration of edible oil. As a national standard method in People's Republic of China (PRC), gas chromatography is a commonly used detection method, which is mainly based on the different fatty acid composition and content of different vegetable oils. After adulteration of peanut oil, the composition and content of fatty acids will change accordingly. By measuring the composition ratio of fatty acids in oil samples, compared with pure peanut oil, the content and types of doping can be determined. In addition, spectral technology is also widely used. However, these methods still have some defects, such as expensive instruments, long analysis time, complicated sample treatment and consumption of a lot of toxic reagents.
In this experiment, spectrophotometry was used as a detection method to detect whether peanut oil was doped with other kinds of edible oil, without any sample pretreatment, only a very small amount (300? L) The oil sample to be tested can be directly analyzed to determine whether it is adulterated or not and its adulterated content. At the same time, compared with the national standard method, the experimental results are satisfactory. This method is simple, rapid and efficient. Based on the different freezing points of oils and fats at low temperature and the different structures of fatty acids contained in different oils and fats, a rapid and simple method for judging peanut oil adulteration was established by monitoring the curve of absorbance of oil samples to be detected at low temperature with time. The influence of cooling temperature on the curve was investigated, and the characteristic absorption peak of the curve was analyzed qualitatively and quantitatively. The test time for a single sample is 25 minutes. Accurately measure 0.5mL of adulterated oil (brown heavy oil, soybean oil, rapeseed oil, corn oil and cottonseed oil) respectively, put them in different containers (colored bottles), dilute them with pure peanut oil to 10ml, and shake them evenly for 15 minutes to make the diluted solution more uniform, thus preparing samples with adulteration content of 5%. Then accurately measure 1.0mL, 2.0mL and 3.0mL of adulterated oil, respectively, to obtain oil samples to be tested with adulterated contents of 10%, 20% and 30%, and pure peanut oil samples without adulteration. Take 300? L put the sample to be tested in a plastic sample cell (cell thickness 0.5cm, volume 1mL), put the sample cell in a constant-temperature heating tank at 37℃ for 10 min, then quickly transfer the sample cell to a detection tank (T=3.0℃), and continuously detect the samples passing through the cuvette every 0. 125 seconds. Record the original light intensity I0 when the cuvette is just put into the detection tank, that is, t=0, and record the light intensity I at other times during the detection process to obtain the absorbance-time curve. Repeat the analysis for each sample and take two averages.