Attenuated Total Reflection Mid-infrared Spectroscopy Combined With Chemometric Methods For The Determination Of Food

With the increasing precision of dietary nutrient recommendations,consumers are paying special attention to the content of nutrients in foods,and the quantitative analysis of food ingredients is increasing.The traditional physical and chemical analysis method has a long analysis time and heavy contamination of reagents.Searching for fast and green detection methods has become a hot spot in food analysis.Near infrared spectroscopy(NIRS)has developed rapidly in quantitative analysis in recent years,but it is mostly used to determine a large number of ingredients in food.The mid-infrared signal is stronger than near-infrared,but it is more commonly used for qualitative analysis.Therefore,this paper explores the application of mid-infrared spectroscopy in quantitative analysis of trace components in food in order to become a method for rapid detection of food.Firstly,the method was proved feasible by the determination of soluble protein in potatoes,then it was further applied to the determination of selenium in rice flour,selenium in selenocystine form and selenium in tea.The following conclusions were drawn:(1)Determination of soluble protein content in potatoes.The Principal Component Regression(PCR)model of the original spectrum after 7-point smoothing and first derivative processing is better and has better prediction ability.The relative deviation is less than 20%,accounting for 70.37%,and the higher content(>5 mg/g)can reach 92.86%,which can basically meet the requirements of preliminary rapid prediction,it shows that the combination of mid-infrared spectroscopy and chemometrics can be used as a method for rapid detection of food ingredients.(2)Selecting 1600-650 cm~-11 as the characteristic band of selenomethionine,the PLS model was established after the first derivative treatment of the original spectrum,the linear fitting coefficient between the predicted value and the real value can reach over 0.98,the relative deviation is as high as 87.5%or more within 20%,and the relative deviation of 72.29%is within 10%,the prediction is accurate.The1600-650 cm~-11 was selected as the characteristic band of selenocystine.The original spectrum was processed by the second derivative to establish the PLS model.the linear fitting coefficient between the predicted value and the real value could reach more than 0.95,the relative deviation between the predicted value and the real value was more than 75%within 20%,and the relative deviation between the predicted value and the real value was more than 92%within 20%for the samples with the concentration of 18 ug/100g,and the high concentration prediction was even more accurate,it is indicated that the attenuated total reflection mid-infrared spectrum can quantitatively analyze trace amounts of selenium in food.(3)The prediction of organic selenium and inorganic selenium in tea is not ideal,but the prediction effect of organic selenium is better than that of inorganic selenium.The ingredients we tested were trace components and were highly susceptible to other factors.Therefore,it is necessary to increase the sample size,expand the range of selenium content,correct the natural sample with the spiked sample,and use the multiple attenuation total reflection accessory to collect the spectrum to improve the signal-to-noise ratio during the test,and consider the secondary influence factor and other means,in order to improve the stability of modeling and prediction.In summary,the attenuated total reflection mid-infrared spectroscopy combined with chemometrics method is partially feasible as a fast and accurate green food detection method,but the determination of some trace components or some components with weaker mid-infrared absorption remains to be further explored.