Evaluation The Quality Of Fresh Tea Shoots By Near Infrared Spectroscopy

At present, the quality of fresh tea shoots is usually appraised by sensoryevaluation, which leading to injustice results vulnerable to subjective factors. At thesame time, it is also the premise of the standardized processing to differentiate theclassification of fresh tea shoots.By selecting the contents related to the quality of fresh tea shoots, quality indexis firstly presented in this paper to evaluate the quality of fresh tea shootsquantificationally.Although it is used to solve the problem of being difficult quantify qualityevaluation of fresh tea shoots by quality index, the traditional chemical methods aretime consuming and laborious, and can not be used for online analysis. Near infraredspectroscopy (NIRS) has been widely used in petroleum, pharmaceutical, tobacco,beverage and food industry due to the advantages of saving time and the convenient.This paper attempts to apply NIRS combined with chemo-metric methods toconstruct calibrate models to predict the quality of fresh tea shoots, in order toproviding an accurate and fast method for tea shoots’ acquisition and processing. Anovel analyzer equipped with a NIRSystem for prediction of fresh tea shoots qualitywas designed by transferring the humidity, total nitrogen and crude fiber NIR models.Huang shan mao feng tea is a product of geographical indication, a method iscalibrated to discriminate the origins of fresh tea shoots by obtaining the featurespectral regions. NIR analysis method for the determination of the contents isaccepted by all over the world, this paper attempts to develop a standard method fordetermination the contents of humidity, total nitrogen and crude fiber in fresh teashoots by near infrared reflectance spectroscopy.The detail results list as follows:1. The formula of quality indexAfter selecting the contents related to the quality of fresh tea shoots, the formulaof quality index was presented: quality index (QI)=(humidity content×totalnitrogen content)÷crude fiber content. QI has positive relationship with fresh teashoots quality and it can evaluate the quality of fresh tea shoots quantificationally.2. NIR analysis models of contents and quality grades in fresh tea shootsHumidity near infrared prediction model. When the full spectrum was dividedinto23sub-interval and MSC mean pretreatment method was used,12sub-interval was selected as feature spectral regions of humidity by biPLS algorithm, and thehumidity LS-SVM model was calibrated with four PCs (accumulating contributionas99.69%) input. The results were that Rcv=0.993, RMSECV=0.006%, Rp=0.989,RMSEP=0.010%.Total nitrogen near infrared prediction model. When the full spectrum wasdivided into21sub-interval and MSCmean pretreatment method was used,10sub-interval was selected as feature spectral regions of nitrogen by biPLS algorithm,and the total nitrogen LS-SVM model was calibrated with four PCs (accumulatingcontribution as99.91%) input. The results were that Rcv=0.997, RMSECV=0.004%,Rp=0.991, RMSEP=0.011%.Crude fiber near infrared prediction model. When the full spectrum was dividedinto24sub-interval and MSCmean pretreatment method was used,6sub-intervalwas selected as feature spectral regions of crude fiber by biPLS algorithm, and thecrude fiber LS-SVM model was calibrated with three PCs (accumulatingcontribution as99.93%) input. The results were that Rcv=0.989, RMSECV=0.102%,Rp=0.973, RMSEP=0.142%.Quality index near infrared prediction model. When the full spectrum wasdivided into24sub-interval and mean pretreatment method was used,5sub-intervalwas selected as feature spectral regions of quality index by biPLS algorithm, and thequality index LS-SVM model was calibrated with four PCs (accumulatingcontribution as99.86%) input. The results were that Rcv=0.984, RMSECV=0.0109,Rp=0.980, RMSEP=0.0152.Quality grade near infrared prediction model. When the full spectrum wasdivided into24sub-interval and MSC pretreatment method was used,4sub-intervalwas selected as feature spectral regions of quality grade by biPLS algorithm, and thequality grade LS-SVM model was calibrated with four PCs (accumulatingcontribution as99.73%) input. The discrimination results were100%in calibrationand prediction sets.3.Near infrared analyzer for the quality of fresh tea shootsBased on the NIR models of humidity content, total nitrogen content and crudefiber content of fresh tea shoots, a novel analyzer equipped with a NIRSystem andgrating spectrophotometer for prediction of fresh tea shoots quality was designed byS/B transferring method through cooperation with Hefei Meiya OptoelectronicTechnology Co., Ltd.. The analyzer could obtain the QI value of fresh tea shoots within one minute, which realized the online quality evaluation of fresh tea shoots,removing the influence of human factors.4.The origin discrimation of fresh tea shootsNear infrared spectroscopy and back propagation-artificial neural network (BP-ANN)model in conjunction with backward interval partial least squares (biPLS) algorithm were usedto determinate the geographical origin of fresh tea shoots in this paper. The tea shoots werecollected from three cities of Hefei, Huangshan and Lu’an. The regions in the near-infraredspectra relevant to geographical origin (12493cm-1to12138cm-1,10700cm-1to10345cm-1,9627.3cm-1to9276.3cm-1,6788.5cm-1to6437.5cm-1,4659.4cm-1to4308.4cm-1and4304.5cm-1to3953.5cm-1) were selected using biPLS algorithm. The first six principal componentsthat explained99.98%of the variability in this spectral data were then used to calibrate theBP-ANN model for determination of the geographical origin of fresh tea shoots. Thediscrimination results were100%.5. Determination of inclusion of fresh tea shoots using near infrared reflectancespectroscopyThe near infrared spectroscopy technology for determination of the inclusioncontent is a new approach to be recognized worldwidely. At present, Europe, UnitedStates and the International Grains Council Organization have developed sieries ofnear infrared monitoring standards. But in the field of tea trade, it is a research gap.Based on the work of determination of the contents of humidity, total nitrogen andcrude fiber, this paper attempts to develop a NIR standard for determination of thethree ingredients in fresh tea shoots.