Change Of Cell Structure And Mechanical Properties Of Yellow Peach During The Hot Air-expansion Puffing Drying

Yellow peach belongs to the Rosaceae family,which is rich in nutrients and has high economic value.It is well received by domestic and foreign markets.Due to the sour taste,easy softening and rot after harvest,the yellow peach is usually made into canned yellow peaches,quick-frozen yellow peaches and other products.In recent years,fruit chips have been popular with consumers because it is crispy and delicious.The drying technology can extend the shelf life of products by removing a large quantity of water.At present,the searches on fruit chips mainly focus on the optimization of drying technology and product quality.There are few studies on the influence of cell structure and mechanical properties changes on the texture of products during the drying process.In this paper,yellow peach was used as the research object.Through researching pectin,hemicellulose and cellulose of peach slices cell wall and studying the changes of cell morphology,pore area and fractal dimension,the changes of cell structure was analyzed during the hot air-expansion puffing drying.By studying the stress-strain curve,elastic modulus,viscosity index,and maximum stress changes,the effects of mechanical properties on cellular structure changes were analyzed during the hot air-expansion puffing drying.The results can provide the theoretical basis for further improving the texture structure of yellow peach slices.The results of the study are as follows:(1)Research on cell wall component: With the increase of the temperature and time,the drying efficiency raised gradually and the water content decreased gradually and the content of pectin,hemicellulose and cellulose of cell wall declined significantly during the hot air drying process(P<0.05).The puffing pressure had no significant effect on pectin,hemicellulose and cellulose of cell wall at the same puffing temperature during the expansion puffing drying.(2)Research on cell morphology: During hot air drying,the higher the temperature was and the longer the drying time was,the more obvious the cell shrinkage of the yellow peach slices was.The average pore area and the maximum pore area of cell were gradually reduced.The fractal dimension of yellow peach slices increased gradually,which indicate the complex and irregular cell morphology of the yellow peach slices during the drying process.During the expansion puffing drying,the effect of puffing pressure on cell morphology of yellow peach slices is less when the puffing temperature is 95°C.As the puffing temperature of 105°C and 115°C,the average pore area of yellow peach slices increased first then started to drop,and the maximum pore area was for 0.3MPa.The effect of pressure on the fractal dimension of yellow peach slices was not significant(P>0.05).(3)Research on mechanical properties: The stress of hot air-dried yellow peach slices increased with the increase of deformation,and the rate of stress varied with different drying time.With the extension of the drying time,the elastic modulus increased first and then decreased for 60°C,and increased slowly first and then decreased rapidly for 70°C,and showed a gradual decline for 80°C.The higher the hot air drying temperature is,the faster the maximum viscosity index is.The viscosity index of 60°C/180 min is only 34% of 80°C/180 min.At the same drying temperature,the maximum stress of yellow peach slices decreased significantly with the extension of the drying time.At the same drying time,the maximum stress is 60°C<70°C<80°C,and the maximum stress of the yellow peach pieces decreased gradually with the temperature increasing.The stress of puffied yellow peach slices raised with the increase of deformation.With the increase of the puffing pressure,the elastic modulus,viscosity index,and maximum stress of the yellow peach slices did not change significantly(P>0.05)at the puffing temperature for 95°C.With the increase of the puffing pressure,the elastic modulus increased slowly,the viscosity index decreased gradually,and the maximum stress decreased first and then increased at the puffing temperature for 105°C.With the increase of the puffing pressure,the elastic modulus increased gently,the viscosity index decreased gradually and the maximum stress increased gradually at the puffing temperature for 115°C.