Identification Of Raisins By Infrared Spectroscopy

There are many kinds of raisins,and the quality of raisins from different producing areas is quite different.Therefore,the rapid and accurate identification of raisins from different producing areas and types has great reference value for consumers and businesses.In this dissertation,184 raisins from Turpan,Hami,Gansu,Qinghai were identified by"Tri-step infrared spectroscopy"（Fourier transform infrared spectroscopy（FTIR）,second derivative infrared spectroscopy（SD-IR）,two-dimensional correlation infrared spectroscopy（2D-IR））and multivariate statistical analysis（principal component analysis（PCA）,cluster analysis（HCA））.The results of original spectra and second derivative spectra showed that the original spectra of raisins from different producing areas and species were similar,mainly composed of glycosides,polysaccharides and flavonoids.The second derivative spectra of raisins from different producing areas and varieties are quite different in the range of 1800～900 cm^-1.The second derivative spectra of black beauty and black currant from different producing areas are significantly different in the range of 1700～1600 cm^-1,1700～1600 cm^-1and 1380～1320 cm^-1,respectively.The strongest peak of Turpan red fragrant imperial concubine at 1055 cm^-1and the peak shift in the region of 1200～1180 cm^-1.Turpan green fragrant imperial concubine has a significant difference in the intensity of raisin absorption peak between Turpan green fragrant imperial concubine and other producing areas in the range of 1800～1250cm^-1and 1160～970 cm^-1.The results of two-dimensional correlation infrared spectroscopy show that there are significant differences in the position,intensity and cross peak of automatic peaks of black beauty in the range of 983～1104 cm^-1,1107～1252 cm^-1,1344～1415 cm^-1and1433～1550 cm^-1,black currant in the range of 1110～1255 cm^-1and 1267～1507 cm^-1,red Xiangfei in the range of 812～957 cm^-1and 1455～1713 cm^-1,and green Xiangfei in the range of 809～1140 cm^-1,1147～1375 cm^-1and 1428～1755 cm^-1,Different kinds of raisins in Turpan have great differences in the position,intensity and cross peak of automatic peak in the range of 876～1084 cm^-1and 1185～1500 cm^-1.The results of principal component analysis and cluster analysis show that,The second derivative spectral data of 1700～1600 cm^-1area are selected for black beauty and black currant from different producing areas,and the second derivative spectral data of 1800～900 cm^-1area are selected for red Xiangfei and green Xiangfei from different producing areas for multivariate statistical analysis（principal component analysis and cluster analysis）.The accuracy of classification of raisins from different producing areas and types is 100%,and the process is simple,In the selected areas,the use of cluster analysis can realize the separate classification of Turpan raisins.The work of this paper shows that the combination of"Tri-step infrared spectroscopy"and multivariate statistical analysis can be used to distinguish raisins from different producing areas and species,which is expected to provide a fast and simple identification method for the study of raisins.