Near-infrared Rapid Detection And Quality Evaluation Of Crocus Sativus L.

Crocus sativus L.is a perennial bulbous herb belonging to crocus of Iridaceae,also known as saffron or crocus.According to the records in pharmacopoeia of the people’s Republic of China,C.sativus has the effects of promoting blood ci Rculation,removing blood stasis,clearing away heat and toxic materials,nourishing cool blood,relieving depression and tranquilizing mind.It is mainly used for treating toxic and warm spots,melancholia,palpitation and postpartum blood stasis amenorrhea.It is widely used in medicine,food,cosmetics and other fields.C.sativus is expensive and in short supply.Therefore,some illegal businessmen often fake C.sativus by using lotus stamen,safflower,chrysanthemum stamen tongue,corn stigma and paper pulp.Traditional identification methods of C.sativus,such as character and microscopic observation,rely too much on the accumulation of experience of appraisers and have certain uncertainty and subjectivity.However,high performance liquid chromatography(HPLC)and gas chromatography-mass spectrometry(GC-MS)have complicated detection process and long time consumption,making it difficult to meet the requirements of on-site detection when pu Rchasing crocuses.Therefore,in this study,near infrared rapid(NIR)detection method capable of qualitative or quantitative analysis for C.sativus samples is adopted,partial least squares(PLS)regression model is established,morphological characteristics of dry crocus stigma obtained by five different drying methods are compared,composition of crocus stigma is analyzed by HPLC,and changes in aroma of dry C.sativus are analyzed by GC.In the resea Rch of rapid qualitative detection technology of C.sativus based on NIR,NIR diffuse reflectance spectra of samples were collected,and partial least squares discriminant analysis(PLS-DA)and PLS regression methods were used to compare the models obtained by different spectral pretreatment methods and spectral interval selection.The results show that the appropriate pretreatment method and the selection of spectral range can improve the performance of the model.In the qualitative analysis of C.sativus,the second derivative is the best pretreatment method.In the quantitative analysis of C.sativus with different adulteration levels,the standard normal transformation(SNV)pretreatment method showed better performance for adulterated lotus stamen in C.sativus.However,the pretreatment method of multiple scattering correction(MSC)showed better performance for adulterated corn stigma in C.sativus.The spectra were divided into 10,20 and 30 intervals.The intervals shown in the table were selected and PLS models were established for each spectrum.The EMSECV and RMSEP values,Rc2 and Rv2 of each model were compared.The results showed that the PLS model of C.sativus adulterated lotus stamen showed the best performance and the highest prediction accuracy when the 4 intervals of 9,23,24 and 29 were selected.The PLS model of C.sativus adulterated corn stigma showed good performance and strong prediction ability and stability when selecting the three intervals of 22,24 and 27.Five different methods of vacuum drying(VD),microwave drying(ID),oven drying(OD),infrared drying(ID)and freeze drying(FD)were used to analyze the morphological characteristics,composition and aroma components of stigma of C.sativus.The results show that different drying methods have significant differences on the experimental results.FD takes up to 47 hours and ID takes up to 0.7 hours.The color value of dried C.sativus obtained by FD is the highest.Scanning electron microscope(SEM)showed that the initial cell structure of pollen grains of FD samples was intact.Meanwhile,FD has the highest content of total crocin and crocin II,which are 31.80% and 6.76% respectively.OD retained the most crocin I(25.41%),and ID retained the most crocin aldehyde.Although OD is the most commonly used drying method for medicinal plants,the experimental results show that FD is the most suitable choice because C.sativus can maintain its integrity,glossiness and the highest crocin content,although FD requires the longest drying time and consumes more energy.In addition,ID has a good effect on the preservation of C.sativus aroma components,and the required drying time is short.