The Study Of The Rapid Determination Of Main Physical-chemical Indexes In Rice Based On IR

Rice is one of the staple food crops around the world.With the development of people's life quality,people begin to pay attention to rice cooking texture.During the processing and storage from rice harvest to sale,as time and environment change,the physical and chemical properties of rice slowly change resulting in the corresponding changes in the rice composition,flavor and taste.Nowadays physical and chemical indicators' changes,such as fatty acid value and protein can effectively reflect the rice freshness.However,the methods of testing these indicators are time consuming,laborious,prone to large errors and are not suitable for measuring large quantities of samples.Meanwhile,DRIFTS and NIRDRS play an increasingly important role in the quality control of food,medicine and agricultural products,and have good application prospects.Therefore,this paper focuses on combining FTIR or NIR with partial least squares(PLS)and Lambert-Beer's law to determinate the content of rice fatty acids,rice protein and gel content rapidly.First of all,this paper focused on the prediction ability of brown rice fatty acid by comparing different organic solvents,then we decided the following experiments were carried out using ethanol and n-hexane sequential extraction.It's a useful way to make the sample interference out of the water peak using ethanol extraction and n-hexane anti-extraction.The spectra were collected by FTIR transmission spectroscopy and their characteristic absorption peak of rice free fatty acids at 1714cm-1.Determination of rice fatty acids is relying on oleic acid as a standard curve,and spectra were analyzed by Lambert-Beer's law.Meanwhile,fixed-point interception,subtraction and baseline correction are good for correlation coefficient of curve.According to calculation,the model can well-reflect the level of the fatty acids in rice,and roughly determine the value of the fatty acids in rice,the error is within the acceptable range of national standards.Then,the rapid detection method of rice protein was studied in this paper.The polished rice flour spectra were collected by DRIFTS spectrum and the NIRDRS spectrum and modeled and optimized by PLS,iPLS and BiPLS method.The best mid-infrared model was obtained as R2=0.96975,RMSECV=0.611,RMSEP=0.568.The best near-infrared model was obtained as R2=0.96071,RMSECV=0.405,RMSEP=0.368.Both methods are highly predicting rice protein content,and the results of mid-infrared are slightly better than near infrared.Finally,the rapid detection method of rice consistency was studied in this paper.The 300 spectra were collected by diffuse reflectance spectroscopy and near-infrared and mid-infrared spectroscopy respectively.The partial least squares was used to analyze the results.The best rice consistency near-infrared model was obtained as R2=0.95784,RMSECV=4.85,RMSEP=3.93;The best mid-infrared model was obtained as R2=0.96581,RMSECV=4.73,RMSEP=4.79.In the accuracy validation,the relative error of DRIFTS ia about 1.22%,as well the relative error of NIRDRS is about 0.72%.Both two models can effectively reflect the consistency of rice grains.In summary,the present study effectively analyzed the contents of protein,fatty acid and gel consistency in rice using FTIR and NIR techniques combined with diffuse reflectance,Lambert-Beer's law and partial least squares.All of the studies have achieved some results.Some of the new methods have been established for the determination of rice physical and chemical indicators,and provide new ideas for the application of rice in the infrared spectra.