Handheld Nondestructive Detector Assessing Internal Quality Of Kiwifruit Based On Multispectral Technology

Kiwifruit in China has high yield and wide planting area,but its market share in the international market is very low,and the annual loss rate due to early picking or over-ripe rot is high.In order to improve economic benefits,reduce production losses,it is urgent to strengthen quality supervision,realize the real-time detection of kiwifruit internal quality,timely judgment of kiwifruit maturity.The soluble solid content(SSC)and firmness are two important internal quality parameters to judge the maturity of kiwifruit.The traditional method of measuring SSC and firemness is a lossy sampling detection method,which takes a long time and causes certain economic losses.Meanwhile,there is no handheld nondestructive detector on the market for the multiple internal qualities of kiwifruit.Multispectral technology is a lower cost and faster nondestructive detection method developed based on visible/near infrared spectroscopy,suitable for the development of handheld detectors.Therefore,according to the functional requirements of users,the embedded hardware and software system with high integration and stability was developed,and the multispectral probe structure was designed,which is suitable for kiwifruit internal quality detection.Finally,the prediction model of kiwifruit SSC and firmness was established,and the accuracy and repeatability of the detector were tested,realizing the real-time,accurate and non-destructive measurement of kiwifruit SSC and firmness.The main research contents and conclusions are as follows:(1)Developed the embedded hardware program of kiwifruit internal quality nondestructive detector.Firstly,a multispectral probe was developed to detect the internal quality of kiwifruit.The light source was LED with patches of 12 different wavelengths(705,735,740,780,810,835,840,860,880,890,935 and 970 nm).The sensor was TSL2561.Plane-convex lens was used to prevent stray light interference.12 LEDs are fixed around the sensor with the best incident angle and distance through the base.Secondly,according to the demand analysis,the functional modular design is adopted,mainly including the main circuit,multispectrum acquisition circuit,temperature sensing circuit,light source driver circuit,input/output circuit and power management circuit schematic and integrated design.(2)Developed the embedded software program of kiwifruit internal quality nondestructive detector.The embedded software program is programmed by C language and adopts the programming method of directly operating registers,which effectively improves the efficiency of spectrum acquisition.In addition,the program portability is improved through the encapsulation of functions,and different graphic interaction interfaces are designed to make the detector easy to operate and achieve a more friendly human-computer interaction.(3)Three different prediction models are compared and analyzed,and the comprehensive performance of the detector is tested.Multivariate linear regression(MLR),least squares regression(PLSR)and support vector regression(SVR)models were established to predict the SSC and firmness of 1516 kiwifruit samples.The results show that the SVR model is superior to MLR and PLSR model.For the SSC and firmness of ’Huayou’ kiwifruit,RP of SVR model were 0.912 and 0.892,RMSEP of SVR model were 1.309% and 0.864 kg,respectively.For SSC and firmness of ’Xuxiang’ kiwifruit,RP of SVR model were 0.799 and 0.820,RMSEP of SVR model were 1.448% and 1.207 kg,respectively.The model has high accuracy and reliability,and has met the needs of practical production.In the process of testing the performance of the detector,firstly,the reliability of the multispectral data collected by the detector was verified,by comparing the influence of different SSC and firmness on diffuse reflectance.Secondly,through different varieties and maturity kiwifruit internal quality testing,as well as the testing of power supply current and voltage found that the measurement results have good repeatability,and the power supply stability of the detector is high.The detector designed in this paper has low hardware cost,handheld,fast multispectral acquisition speed and high efficiency.The detector weighs only 380 g and can measure a sample in 2 s,with good reliability and repeatability.The research results are used to guide the production,harvesting,sales and processing of kiwifruit and other industry chain internal quality inspection links.