Geographical Origin Discrimination And Quality Control Study Of Chinese Wolberry By Near-infrared Spectroscopy

Chinese wolfberry is good for our health.It can be used both as food and medicine;it is one of the favorite foods for people.However,Chinese wolfberry suffers the differents of qualities which can lead to affect its edible and medicinal purpose.It is necessary to establish an effective automatic detection method for contoling the quality of Chinese wolfberry.The study took Chinese wolfberry from different regions of China as raw materials,acquired the Chinese wolfberry by near-infrared spectrometer and then got the polysaccharide,total sugars and crude fat content by chemical analysis.Near-infrared spectroscopy(NIR)spectral data of wolfberry samples were analyzed with distance-discrimination analysis and cluster analysis to discriminate their geographical origins.Calibrations of Chinese wolfberry were developed and validated for determination of the polysaccharide content,total sugars content and crude fat content using partial least squares technique(PLS).It showed that NIR spectroscopy could be the non-destructive detection of Chinese wolfberry.The main research results were as follows:(1)To develope automatic and quick method to determine the geographical origin of Chinese wolfberry from Zhongning,thirty-five Chinese wolfberry samples from different regions of China were scanned with a near-infrared(NIR)spectrometer.NIR spectral data of wolfberry samples were analyzed with distance-discrimination analysis and cluster analysis to discriminate their geographical origins.The results of the distance-discrimination analysis indicated that good prediction results were achieved with 100%recognition rate of the origin of wolfberry based on the multiplicative scatter correction and standard normal variate transformation of spectral data ranging from 6500cm-1 to 5200cm-1.The wolfberry samples could be clustered into two groups using the Mahalanobis distances combining with the Ward’s method.The wolfberry from Zhongning,Ningxia were classified into one group and those from other regions as one group.The recognition rate was 96.9%.In conclusion,it is feasible to apply NIR to discriminate geographical origin of Chinese wolfberry from Zhongning.(2)For automatic determination of polysaccharide content of Chinese wolfberry,calibrations were developed and validated for determination of polysaccharide content by near-infrared spectrometer.The correlation coefficient(R),root mean square errors of calibration(RMSEC),root mean square errors of corss validation(RMSECV)and the root mean square errors of prediction(RMSEP)of the calibration for polysaccharide were 0.9948,0.0707,0.6844 and 0.0883 in range of 8360～5660cm-1 with first derivative and standard normal variant(SNV).And the number of principal component is 4.(3)Using NIR diffuse reflectance spectroscopy as a rapid and non-destructive method for the determination of total sugars content of Chinese wolfberry,The optimal NIRS modeling method were that pretreatment method was first derivative and standard normal variant(SNV),NIRS region was 6400～4780cm-1 and apply smoothing process(Savitzky-Golay smoothing method and smoothing point 7)to filter noise and the number of principal component was 7.The model parameters were that R value achieves 0.99998,RMSEC was 0.0419,RMSECV was 4.1595 and RMSEP achieved 0.489.(4)The optimal NIRS modeling method of crude fat content were that pretreatment method was first derivative and multiple scatter correction(MSC),NIRS region was 6905～4240 cm-1 and apply smoothing process(Savitzky-Golay smoothing method and smoothing point 5)to filter noise and the number of principal component was 4.For crude fat the correlation coefficients calibration(R2),the root mean square errors of calibration(RMSEC)and root mean square errors of corss validation(RMSECV)and the root mean square errors of prediction(RMSEP)were 0.9889,0.154,0.9246and 0.174,respectively.Therefore,good prediction results were achieved.The results indicated that NIR spectroscopy technique with PLS offers effective quantitative capability for polysaccharide,total sugars and crude fat content in Chinese wolfberry.