The Development Of Portable Detection Device And Model Study For Fruit Sugar Content And Shelf Life

Near-infrared reflectance spectroscopy(NIRS)could provide powerful technical support for rapid nondestructive detecting the internal quality of agricultural products.Portable detection instrument has been widely favored by people for characteristics of small size,low price,portability and simple operation.The feasibility was discussed for enhancing the detection accuracy by optimizing structural parameters for the portable infrared detector.The paper took mass fruits as research objects to recorded near infrared transmittance spectroscopy.The optimal structural parameters have obtained finally.Besides,the feasibility of qualitative detection of pear shelf life was investigated by near infrared diffuse reflectance spectroscopy.These models which were established by near-infrared reflectance spectroscopy were comparative analyzed,the least squares support vector machine(LS-SVM)and partial least squares(PLS)discrimination models of pear shelf life were established.At the same time,the optimal qualitative detection model of pear shelf life was conducted.Finally,the portable detection instrument has been designed and developed by the best structural parameters which obtained from the experiment,and the function of the portable detection instrument were tested by experiments.The analysis of both experimental methods and conclusions of this study were described as below:(1)The influence on the accuracy of probe with different structural parameters was investigated for detecting sugar content of apples by near-infrared reflectance spectroscopy.The spectrums were recorded with different structural parameters by self-designed instrument.Eight tungsten halogen lamps were installed in probe.The power of each lamp was 1.5 watt.The light sources were installed around the samples,and the detector received light from the bottom of the fruit cup.Meanwhile,two structural parameters light source angle?and distance between light source and probe W were analyzed for investigation of the influence of the response properties of visible-NIR spectra.The partial least square regression model and least squares support vector machine model were built with the spectra,by comparison,partial least square regression model obtains better performance.The best performance was improved with the root mean square error of prediction(RMSEP)set of 0.334°Brix and the correlation coefficient of prediction set of 0.924 when the spectral were recorded with illumination angle for 45,and the distance between probe and light source was 15mm.The research can provide technical support and reference basis for portable detection designing.(2)The relationship between the related indexes of quality and shelf life of pears was explored for detecting sugar content of pears by near-infrared reflectance spectroscopy.The near-infrared reflectance spectrums of pears were recorded by self-designed instrument.The NIR spectra response properties of the pears in different shelf life were analyzed.Then the principal components analysis(PCA)?discrimination partial least square(DPLS)and least squares support vector machine(LS-SVM)were developed for the discrimination of shelf life of pears.According to the principle of minimum misjudgement rate,through the comparison of three models prediction,the LS-SVM model which was established by 16 kernel variables as input and the linear kernel functionas variable is the best model,and the misjudgment ratio decreasing to 0%.The study established an accurate prediction model of fruit quality in shelf-life,it had great significance for the quality monitoring and shelf life prediction of fruit shelf life.(3)A micro STS spectrometer was used as a spectral acquisition unit for portable instrument.After selecting the core components such as the core board and circuit board,the circuit design,the layout of the optical system and the integration of the software were carried out.Finally,a near infrared detector for detecting the internal quality of fruit was designed and developed by ourselves.The instrument has the advantages of small size,low cost,high detection precision and short detection cycle.Taking the apple as the research object and using Portable instrument to do the Test verification,the partial least squares prediction model of apple soluble solids content was established by using it,the prediction correlation coefficient is 0.911 and the root mean square error is 0.532°Brix.Based on the microspectrometer of STS,the results show that it is feasible to detect fruit internal quality by using portable fruit internal quality detection which was designed and developed by ourselves.