Research On Correlation Analysis Between Optical Properties And Internal Quality Of Kiwifruit Growth And After Harvest

Kiwifruit is rich in nutrients and contains many amino acids and vitamins that the human body needs.With the improvement of living standards,people pay more and more attention to the quality of fruit.Sugar,firmness and moisture content are the main factors affecting the quality of kiwifruit,while the near-infrared and hyperspectral techniques are commonly used non-destructive testing methods.However,the internal structure of kiwifruit is relatively complex.Traditional near-infrared spectroscopy cannot provide separate information for absorption and scattering,so that the information carried by light cannot be clearly described.In order to study the variation of absorption and scattering characteristics of kiwifruit,and the correlation between absorption and scattering characteristics and physicochemical parameters,a detection system of the optical parameters of kiwifruit tissue was established in this paper.The optical parameters(absorption coefficient,reduced scattering coefficient),quality parameters(total sugar,total acid,firmness,moisture content,SSC),physical parameters(mass,transverse and longitudinal)of ’Huayou’ and ’Hayward’ kiwifruit in different periods were measured.The variation rules of absorption coefficient and reduced scattering coefficient of kiwifruit and its correlation with total sugar,total acid,firmness,moisture content and SSC were studied.The major work and conclusions were as follows:(1)The kiwifruit tissue optical parameters detection system was designed and verified.Based on a single integrating sphere technology,an optical parameter measuring system consisting of an integrating sphere,a spectrometer,and a light source was designed.The optical properties of this system had been tested using intralipid solutions.(2)The absorption coefficient and reduced scattering coefficient of the flesh and skin tissue of ’Huayou’ and ’Hayward’ kiwifruit were studied,during the growing period(from 30 days to 100 days after flowering).The absorption coefficient of kiwifruit flesh during growth period had absorption peaks at 673 nm,975nm,and 1400 nm,and at 673 nm,the absorption coefficient decreased with the growth of kiwifruit.The reduced scattering coefficient spectrum of kiwifruit flesh during growth period was flatter than the absorption coefficient spectrum,and the peak was not obvious.The reduced scattering coefficient of ‘huayou’kiwifruit in the range of 550～700nm and 950～1650nm increased with the growth of kiwifruit.The reduced scattering coefficient of kiwifruit was much larger than its absorption coefficient,and kiwifruit was a highly scattering material.The absorption coefficient and reduced scattering coefficient of kiwifruit skin during growth period were higher than that of the flesh,especially in the range of 550～670nm,the reduced scattering coefficient of skin was about5～10 times of the absorption coefficient of skin.(3)The physicochemical parameters of kiwifruit during growth period were studied,and the correlation between the optical parameters and physical and chemical parameters of the fruit during growth period was analyzed.The results showed that for ’Huayou’ kiwifruit,the best correlation between the absorption coefficient and the total sugar and moisture content appeared in 688-695nm(chlorophyll sensitive area),and the correlation coefficients were-0.73 and 0.66 respectively,and then appeared around 1400nm(water sensitive area),the correlation coefficients were-0.66 and 0.62 respectively.In the range of 690 nm and1090～1340nm,the correlation coefficient between the reduced scatter coefficient of the’Huayou’ flesh and total sugar and moisture content was good,the correlation coefficients were 0.83 and-0.70,and 0.83 and-0.75 respectively.For ‘Hayward’ kiwifruit,the correlation between the reduced scattering coefficient and the total sugar and moisture content was best in the range of 1090～1340nm,and the correlation coefficient were 0.66 and-0.84,respectively.(4)The absorption coefficient and reduced scattering coefficient of the flesh and skin tissue of ’Huayou’ and ’Hayward’ kiwifruit were studied,during the storage period(14 days to84 days after harvest).The change trend of the absorption coefficient of the kiwifruit flesh of’Huayou’ and ’Hayward’ during the storage period was the same,with obvious peaks near the673 nm,975nm,1180 nm and 1400 nm bands.The reduced scatter coefficient of kiwifruit flesh decreased with the increase of storage period,which was opposite to the change trend of the reduced scattering coefficient of growth period.The reduced scattering coefficient of kiwifruit flesh during storage was about 3～5 times of its absorption coefficient.(5)The physicochemical parameters of kiwifruit during storage period were studied,and the correlation between the optical parameters and physical and chemical parameters of the fruit during storage period was analyzed.The results indicated that for ’Huayou’ kiwifruit,the best correlation between the absorption coefficient and total sugar appeared at 702nm(R=-0.53),and the absorption coefficient and firmness(R=0.45)and moisture content(R=0.37)has the best correlation in the range of 660～670nm.For ‘Hayward’ kiwifruit,the best correlation between the absorption coefficient and moisture content and firmness appeared at715 nm and 1650 nm,and the correlation coefficients were 0.4 and-0.47,respectively.In the range of 950～1358nm,the correlation between reduced scattering coefficient and moisture content and firmness were the highest,which were 0.74 and 0.77,respectively.The results showed that the optical parameters of the kiwifruit flesh changed as the kiwifruit matures.The correlation between optical parameters and physical and chemical parameters of kiwifruit during growth period was better than that of postharvest storage,and the correlation between reduced scattering coefficient and physical and chemical parameters was better than that of absorption coefficient.The results of this study have a certain guiding role in understanding the relationship between the optical parameters and physical and chemical properties of fruits and the development of non-destructive testing instruments for fruit quality.