Design And Implementation Of Apple Sugar Detection Based On Infrared Spectrum

As a decisive factor in measuring the quality of apple,the sugar content is usually considered by consumers,apple growers,suppliers and quality supervision departments.Yet,the traditional apple testing method is unsatisfactory due to its destructive,time-consuming and complicated characteristics,which does not meet people's needs.But nowadays,the near-infrared nondestructive testing technology,with high efficiency,convenience and nondestructive quality,represents the trend in testing the sugar content of apple.Based on the near-infrared spectrum quantitative principle and electronic technique,Red Fuji apple as the research object and sugar content of apple as testing index,a real-time,fast,low-consuming and low-cost testing system is studied and designed in this paper.First,the micro fiber optic spectrometer is adopted to collect near-infrared diffuse reflection spectrum of apple.Then,a correlation analysis is made between near-infrared diffuse reflection spectrum and the actual sugar content of apple,thereby determining the near-infrared characteristic wavelength of sugar content-980 nm.Meanwhile,the diffuse reflection light intensity signal,produced when irradiating the apple surface with 980 nm laser diode as the light source,can be detected by the photoelectric detector.Then based on the experiment,it establishes a prediction model of sugar content that is correlated to diffuse reflection light intensity signal and verifies the model.It turns out that the correlation coefficient r of actual sugar content with predicted value is 0.752,with root-mean-square error standing at 1.182.Second,it designs and develops the light path,hardware circuit and system software of this test system.Among them,the light path,including emitted light source and receiving detector,is to collect the near-infrared diffuse reflection light signal of apple.The hardware circuit consists of the light signal processing which is to receive and process the light intensity signal data,and the temperature compensation measuring environment temperature.The system software is to control the light intensity signal emission,collection and temperature measurement by interrupting key;gain the sugar content of apple through inverting the received light intensity signal with the prediction model preset in the system;then,to compensate the sugar content measurement according to the external temperature.In this way,the sugar content value of apple can be displayed on LCD screen.Finally,the sugar content of several apples is tested by the system under different temperature,and a comparative analysis is conducted between test result and actual value.As shown in the experiments under different illumination,temperature,repeatability and system accuracy test,the absolute value of absolute error of system can be controlled within 2Brix%(sugar content),the average value of absolute value of absolute error keeps within 1.5Brix%,the absolute value of relative error within 18%,and the root mean square error is 1.521.Therefore,the stability and accuracy of system achieves a nondestructive effect in testing the sugar content of apple.