Determination Of Fatty Acid Value Of Paddy By Infrared Spectroscopy Method

Paddy is an important source of dietary intake in China.The fatty acid value is a key index to measure the quality of paddy.At present,the national standard method has the disadvantages of ethanol extraction,long analysis time and the difficulty for automatic operation.It is of great significance to develop new method to rapidly detect the fatty acid value of paddy,which would be helpful for the quality guarantee of paddy product,the quality control of grain storage enterprises and the quality supervision by goverment department.In this thesis,infrared spectroscopy methods were used to detect the fatty acid value of paddy,which have the advantages of short analysis time,good versatility and wide application.Firstly,the diode array near infrared spectrometer was used to scan paddy and brown rice powder,and the diffuse reflectance spectra was obtained.The calibration model was constructed and optimized by the analysis software.The results showed that the fatty acid value model of paddy with near infrared reflectance spectroscopy was better than that of brown rice flour,and the residual predictive deviation was 3.45.It can be used for direct quantitative detection of fatty acid value of paddy,which could reduce the complicated pretreatments of paddy husk,grinding powder and so on,and greatly save the detection time.Secondly,the fatty acid value was measured by Fourier transform infrared spectroscopy combined with Lambert Bill's law.After the paddy husk and grinding powder,four kinds of organic solvents were used to extract fatty acids.It is found that the extraction of free fatty acids with methanol or ethanol simultaneously had a large amount of water,and triglycerides were extracted simultaneously with hexane or toluene extraction,which interfereed with the infrared spectrum,resulting in high experimental error.The results showed that after solvent extraction of fatty acids from brown rice the influencs on absorption peak of Fourier transform infrared spectroscopy were quite large and the fatty acid value could not be quantified.The method needed to be improved further.Finally,the fatty acid value was measured by diffuse reflectance Fourier transform infrared spectroscopy.By scanning the samples of brown rice flour,the spectrum was collected.The calibration model was set up,and then the model was optimized by the partial least square method to improve the calculation accuracy.The results showed that the relative error between the infrared detection value of 150 mesh rice flour and the national standard method was quite low(1.63%),and the linear correlation coefficient(R2)was 0.9965.The accuracy was good.It can be used for the detection and analysis of fatty acid value of daily paddy.In general,new infrared spectrum-based methods were developed for detecting the fatty acid value of paddy.The feasibility of two methods was confirmed.The near infrared diffuse reflectance spectroscopy can be used to detect paddy directly,and the diffuse reflectance Fourier transform infrared spectroscopy can be used for the detection of brown rice flour.