Development On Nondestructive Sugar Content Detector For Kiwi Fruits

Kiwi fruit is pretty popular among the public due to its good taste,comprehensive nutrition and rich Vitamin C.Sugar content is one of the essential indicators of kiwi fruit internal quality.Detecting the sugar content of kiwi fruits in the process of production,transportation and consumption can help to control its quality,thus increases economic benefits.The traditional method used to detect sugar content is destructive,in other words,it can only be used for sampling inspection.NIR spectroscopy is with features of non-destruction,high efficiency and low cost.It is widely used in the field of nondestructive testing of agricultural products.At present,there has been much theoretical researches on nondestructive detection of kiwi fruits sugar content by NIR spectroscopy,and good results have been achieved.However,there is no nondestructive detecting instrument on kiwi fruit.Therefore,the purpose of this paper is to use NIR spectroscopy to develop a portable nondestructive detector on sugar content of kiwi fruits.Based on the NIR spectroscopy,key components such as spectral data gathering module,fiber optics probe,light source module,control circuit and control software were selected and designed.The first and second generations of sugar content nondestructive detectors of kiwi fruit were developed based on the spectrum detection devices--USB4000 micro VIS/NIR spectrometer and STS micro NIR spectroscopy.Based on the spectral data of“Xuxiang”kiwi fruit collected using the portable detectors,the partial least squares(PLS)model of kiwi fruit sugar content were established,and the detection accuracy of sugar content in kiwi fruits was tested.The major work and conclusions are as follows:(1)The fiber probe and the light source module were designed for portable nondestructive sugar content detectors of kiwi fruits.Through the test and analysis on the standard reflective fiber probe and the laboratory halogen light source,it was found out that both of them were not suitable for developing portable kiwi fruit nondestructive sugar content detectors.Based on analysis on the structure of kiwi fruit and the light path configuration of spectra collection,the diffuse reflection mode was tested as the best way to collect the kiwifruit spectrum.The fiber probe that could collect diffuse reflection spectrum was designed.Then,the light source module of the portable detector was designed upon micro halogen bulbs.(2)The portable nondestructive sugar content detector of kiwi fruits was developed based on USB 4000 micro VIS/NIR spectrometer,and the sugar content prediction model for“Xuxiang”kiwi fruits was established.The control circuit was designed based on USB 4000micro VIS/NIR spectrometer as spectral collection module and x86 tablet computer as the control platform.The graphical control software was developed by Java programming language.The diffuse reflection spectra of“Xuxiang”kiwi fruit were collected through the detector,and the sugar content prediction model on“Xuxiang”kiwi fruit was established.The correlation coefficient of the calibration set was 0.94.The root mean square error of the calibration set was 1.03~oBrix.The correlation coefficient of the prediction set was 0.95,and the root mean square error of the prediction set was 1.07~oBrix.The prediction model was imported into the detector,implementing the function of sugar content detection.(3)The second generation of the portable nondestructive sugar content detector for kiwi fruits was developed based on STS micro NIR spectrometer,and the sugar content prediction model for“Xuxiang”kiwi fruit was established.Since STS was smaller in size and lighter in weight,the second generation of kiwi-specific diffuse reflective fiber probe was designed based on the STS micro NIR spectroscopy as spectral collection module.The control circuit was designed based on ARM embedded system exploitation board as the control platform.An easier control software was developed by Python programming language.The diffuse reflection spectrum of“Xuxiang”kiwi fruit was collected through the detecting instrument,and the prediction model of the“Xuxiang”kiwi fruit sugar content was established.The correlation coefficient of the calibration set was 0.86.The root mean square error of the calibration set was 0.67~oBrix.The correlation coefficient of the prediction set was 0.83,and the root mean square error of the prediction set was 0.68~oBrix.The prediction model was imported into the detecting instrument,implementing the function of sugar content detection.