Kiwifruit Quality Detection Technology Based On Rheological Properties And Dielectric Properties

Kiwifruit,also known as "King of Vc",is very popular among consumers owing to its sweet and soft taste with a pleasant scent and plenty of nutrients.China is the world's largest producer of kiwifruit,ranking first in the world in terms of area and production.The yield of kiwifruit in the province of Shaanxi alone exceeds 50%of the total kiwifruit production in the country.The quality of kiwifruit affects its economic value and plays an extremely important role in the process of storage,transportation and processing.However,the existing quality detection technology of kiwifruit has the disadvantages of long time,complicated operation,fruit damage,and inability to monitor fruit quality in real time.Based on the factor analysis method to extract the quality features of kiwifruit,the stress relaxation characteristics,creep characteristics and dielectric properties of kiwifruit were studied and the kiwifruit quality prediction model was obtained.The conclusions are as follows:1.The quality features of 16 indexes of kiwifruit were extracted by factor analysis,including Vc,soluble solids,?E,hardness,cohesiveness and elasticity.2.The optimal conditions for testing the stress relaxation features of kiwifruit are:deformation amount is 0.5mm,loading time is 50s,loading speed is I.Omm s-1.The result showed that seven-component Maxwell model has the best effect on the stress relaxation behavior of kiwifruit and R2 can reach to 0.999.There was also a strong correlation between the quality features of kiwifruit and the stress relaxation characteristics.The correlation coefficient between equilibrium elastic coefficient Eo and kiwifruit quality index was higher than other stress relaxation parameters(P<0.01),indicating that the mathematical model of stress relaxation can accurately predict the quality features of kiwifruit.The parameters can well reflect the quality characteristics of kiwifruit.Quality features of kiwifruit such as Vc,soluble solids,?E,hardness,cohesiveness and elasticity can be predicted well by using the ridge regression method to establish the mathematical model with stress relaxation parameters,and the decision coefficients of the model to the validation set are 0.882,0.880,0.869,0.691,0.733 and 0.814,respectively.Therefore,these results draw the conclusion that the stress relaxation characteristics can be used to predict the quality features of kiwifruit.3.The optimal conditions for testing the creep characteristics of kiwifruit are:load is 11 N,loading time is 30 s,loading speed is 1.0mm s-1.The creep behavior of kiwifruit can be described by the four-element Burgers model with and R2 can reach to 0.989.The correlation between Vc,?E,hardness,cohesiveness and elasticity is very significant(P<0.01)with the elastic parameters Ei and E2,the viscous parameters ?1i and ?2 and second order of elastic parameters,which proves that the strong relationships between the quality features of kiwifruit and the creep characteristic parameters so that the creep characteristic parameters can reflect the characteristic quality of kiwifruit well.The stepwise regression method is used to establish the mathematical model of the creep characteristic parameters and its quadratic term and the quality features of kiwifruit,Vc,soluble solids,?E,hardness,cohesiveness and elasticity can be predicted well.The decision coefficients of the model to the validation set are 0.938,0.813,0.883,0.941,0.860,and 0.851,respectively.Therefore,the results draw the conclusion that these creep characteristics can predict the characteristic quality of kiwifruit.4.Both SPA algorithm and GA-PLS algorithm can effectively extract feature frequency and promote data reduction.The dimensional reduction effect of SPA is better,and GA-PLS has better effect in modeling.The spectrum can better characterize the dielectric properties of kiwifruit during neural network modeling.The optimal model selection for the six characteristics of Vc,soluble solids,?E,hardness cohesiveness elasticity,are SPA-NN,GA-PLS-NN,SPA-NN,GA-PLS-NN,GA-PLS-NN,GA-PLS-NN,respectively.The model can predict the six characteristic indicators well and the decision coefficients of the verification set can reach to 0.971?0.922?0.934?0.984?0.908 and 0.954respectively.It is indicated that the dielectric properties can reflect the quality of kiwifruit and lay a foundation for the detection of kiwifruit quality.The stress relaxation,creep and dielectric properties of kiwifruit can predict their quality with fast,efficient and non-destructive features.This research provides a theoretical basis for the rapid detection of quality in kiwifruit picking,storage,transportation and processing,and is of great significance to the development of kiwifruit industry.