Study On Compression Damage And Quality Deterioration Mechanism Of Citrus Reticulata Blanco

Aiming at the problem of compression mechanical damage during harvest,storage,transportation and processing of Citrus Reticulata Blanco,this paper starts with the mechanical properties of Citrus Reticulata Blanco and studies the mechanical properties of Citrus Reticulata Blanco under different load conditions.Multi-factor orthogonal test,analyzed the influencing factors of the mechanical property index and determined the main order level of its influence;through the experiment to determine the mechanical parameters of Citrus Reticulata Blanco peel and pulp.With the help of ANSYS finite element software,the mechanical damage of peeled citrus was simulated,and the damage caused by different degrees of compression was quantitatively evaluated by taking damage pictures and MATLAB image processing methods,and a prediction model of the degree of compression damage rate was established.Through damage test and storage test,the effect of different degrees of compression damage on the storage quality of Citrus Reticulata Blanco and its quality deterioration mechanism were studied.This article can provide a theoretical reference for the prediction of damage and the protection during harvesting and processing.The main contents and conclusions of this article are as follows:(1)Through single factor experiment and orthogonal experiment,the mechanical properties of Citrus Reticulata Blanco were studied,and the relationship between each factor and the mechanical properties of Citrus Reticulata Blanco was analyzed.The single-factor results show that the direction of compression,loading rate and type of compression head have a significant effect on the rupture force of citrus,the total deformation energy and the amount of deformation(P<0.01),and the effects of the direction of compression and the type of compression head on contact stiffness were very significant(P<0.01).The regression equations of loading rate and mechanical property indexes are established,and the determination coefficient R~2was greater than 0.8.Correlation analysis results show that the hardness was significantly positively correlated with the elastic modulus and deformation(P<0.05),the ultimate failure force was significantly positively correlated with the total deformation energy(P<0.05),and the elastic modulus was correlated with the total deformation failure There was a significant positive correlation(P<0.01),a significant negative correlation with the amount of deformation(P<0.05),a positive correlation with the total deformation failure energy(P<0.05),and a significant negative correlation with the contact stiffness(P<0.01).Orthogonal test results show that the compression direction,loading rate and type of compression head have different effects on the mechanical properties of citrus.The compression direction had the greatest influence on the hardness and elastic modulus.The loading rate had an important influence on the type of compression head.The total deformation energy,deformation amount and contact stiffness had the greatest influence.A mathematical model between multiple factors and various indexes was established.The regression coefficients for the rupture force,elastic modulus,total deformation energy,deformation and contact stiffness were all above 0.8,and the hardness was 0.74.(2)Through the mechanical property test,the mechanical parameters of the Citrus Reticulata Blanco peel and pulp were determined:the peel elastic modulus was9.842MPa,the Poisson's ratio was 0.47,and the ultimate stress was 1.314MPa.The pulp elastic modulus was 0.305MPa,the Poisson's ratio was 0.42 and the ultimate stress was 0.083MPa.Through the ANSYS finite element software,the simulation of Citrus Reticulata Blanco under different extrusion loads was carried out.The conclusions are as follows:when the compression deformation was 4 mm,the citrus is more likely to not suffer mechanical damage.When the compression deformation was8 mm,the citrus peel and pulp stress were increased,but the possibility of mechanical damage was not high.When the compression deformation was 12mm,the citrus was likely to have internal mechanical damage,and the citrus peel was still intact and not broken.When the compression deformation was 16mm,the peel and pulp of the citrus are subject to a greater degree of mechanical damage,and even the whole was crushed and broken.(3)With the help of the Image Process Toolbox image processing tool in MATLAB software,quantitative evaluation of the mechanical damage of Citrus Reticulata Blanco under different degrees of compression.After a series of image processing processes,the pixel area of the damaged part and the total pixel area of the pulp are obtained,and the ratio of the two is used to obtain the citrus pulp damage rate,and the crush damage of the citrus pulp is quantitatively evaluated.The results obtained are as follows:the greater the degree of extrusion,the greater the damage rate of citrus.The degree of squeezing had a significant effect on the citrus damage rate(P<0.01).The LSD multiple comparison results showed that there was no significant difference in the damaging rate between the 4mm squeezed citrus and the control group of citrus(P>0.05).There are significant differences(P>0.05).Regression analysis was performed on the compression degree and damage rate,compression force and damage rate of Citrus Reticulata Blanco,respectively.The coefficients R~2of the equation were 0.963 and 0.990,respectively.The results showed that the compression degree of Citrus Reticulata Blanco should not be greater than8mm,and the compression force should not be greater than 34.5N.(4)Through the damage test and storage test,the changes of various quality indicators of Citrus Reticulata Blanco during storage period under different degrees of compression damage are analyzed.The main conclusions are as follows:the degree of compression less than 8mm had no significant effect on the hardness,respiration strength,soluble solids(TSS),titratable acid(TA),and acetaldehyde content of Citrus Reticulata Blanco during storage.The degree of compression more than 12mm,significantly reduced the hardness of Citrus Reticulata Blanco during storage,increased the respiration rate,reduced the soluble solids(TSS)and titratable acid(TA)content of citrus,significantly increase the content of ethanol and acetaldehyde,which caused the quality of Citrus Reticulata Blanco declined significantly.The more severe the compression was,the more obvious the quality deterioration was.For citrus with4mm and 8mm compression,the total number of rots was not significantly different from the control group at 40d storage;for citrus with 12mm and 16mm compression,the total rots were significantly more than the control group at 40d storage.Compression will cause some damage to the pore structure of the citrus epidermis.The more severe the extrusion was,the more severe the destruction of the pore structure was.When the extrusion degree is greater than 12mm,the pores of the citrus epidermis have been completely destroyed.