Study On Analysis Of Moisture Content And Trans Fatty Acid Content In The Edible Oils By FTIR

Edible oil is a daily necessity andindispensable nutrition.As a necessity of diet, edible oil can not only provide a variety of nutrients including required fatty acids for the human body, but also effectively improve the food color, flavor and shape which can increase appetite. With the development of market demand, a series of oil products such as soybean oil, olive oil, rapeseed oil, corn oil, peanut oil, sesame oil, and so on appear on the family tables.It is 30 million tons that vegetable oil is consumed in China per year and more than 20 kilograms of edible oil per person. At present, the quality of edible oil which is evaluated by many indexes including color, odor, moisture and volatile matter, insoluble impurities, acid value, peroxide value and so on is worrying.It is subjective, time-consuming, laborious, and polluting environment in traditional chemical methods, so a new method which is fast and accurateis very important and will be the future development trend. Mid-infrared spectroscopy method takes large advantage in overcoming these problems and shows to be a good means. In this paper, refined edible oil as the research object, to develop research on determination of moisture content and trans fatty acid content in the edible oils by mid-infrared spectroscopy technique.Firstly, FTIR analysis of moisture content in edible oils including soybean oil, olive oil, canola oil, corn oil, and sunflower oil coupled with solvent extraction was examined in this paper and it suggested that acetonitrile is the optimal extraction solvent. When it is less than 300 μg/g, initial moisture in acetonitrile has no significant effect on its extraction capability. The optimal ratio is 1.5~2:1 between acetonitrile and edible oil. When quantitative analysis is based on gap-segment 2nd derivative processed spectra, it is more accurate than others based on differential spectra. It has higher sensitivity in the 1631 cm-1 as opposed to the 3630 cm-1 and 3541 cm-1. Under these optimal conditions, For all the tested samples, FTIR results matched with those determined by Karl Fisher method well, and showed good accuracy and precision(with a SD of ~30, CV of 3%). It is suggested that analysis of moisture in edible oil by FTIR combined with solvent extraction is feasible.Secondly, the auxiliary acetonitrile extraction coupled with D2 O FTIR method, standard spectra recorded at different concentrations of chemicals in the same conditions, then do the spectral subtraction difference spectra obtained at different concentrations of the standard value, then on the second order derivative of the difference spectrum, reading the maximum absorption peak intensity at 1590-1670cm-1, draw the standard curve. Then analyze the impact on the accuracy of different D2 O, the results show that when an excess of D2 O 20-100 times, the error of the measured results were within 5%, but the D2 O optimum dosage of 40 times the measured moisture.The results of the extraction with the assistant of D2 O and analysis showed high precision, good accuracy, low viscosity which means continuous sampling and high flux. It also can significantly improve the baseline absorption and enhancethe split of peaks, which mean better accuracy oftrace analysis in edible oil.Then, methyl trans-linoleic proportionally was added into soybean oil, rapeseed oil, peanut oil to build infrared spectroscopy combined with the establishment of a partial least squares analysis tools model. After the optimization model was determined by selecting the optimal band, it was achieved that rapid and accurate determination of trans fatty acids in edible oils. The results of the comparison analysis showed that modeled at the 990-930cm-1, horizontal attenuated total reflectance Fourier transform infrared spectroscopy and transmission Fourier transform infrared spectroscopy are suitable for rapid determination of trans fatty acids. In contrast, the transmission method showed a significantly better linear relationship and accuracy, a higher sensitivity with samples in which content of trans fatty acidwas <0.5% and a high reference value.