| Begonia fruit is a kind of fruit with extremely rich nutrients,which is consumed in the world today.Drying is the main way to preserve dried fruit for a long time.The drying method effectively prolongs the shelf life of dried fruit,but due to different texture and biochemical changes,the loss of sensory and nutritional quality is considered inevitable in the traditional drying process.In this study,on the basis of single factor experiment,the response surface method was used to optimize the color difference,hardness,brittleness and water content of crabapple fruit as evaluation indexes.The three quadratic linear regression equations of hot air,microwave and vacuum drying methods were established respectively,and the optimal parameters of the three drying methods were obtained.At the same time,the texture,sensory,nutrition and microstructure of dried crabapple fruit under the optimal parameters were measured and compared.The results are as follows :1.Three factors(drying time,drying temperature and material thickness)were selected in the single factor test.The optimal parameters of hot air drying were determined by Box-Behnken response surface optimization test.The time was 6 h,the temperature was 63 °C,and the material thickness was6 mm.Under these conditions,the hardness of crabapple fruit was 77.00 N,the brittleness was 8.00,the color difference was 44.00,and the moisture content was 8 %.2.Three factors(microwave time,microwave power and material thickness)were selected in the single factor experiment.The optimal parameters of microwave drying were determined by Box-Behnken response surface optimization test.The power was 30 W,the time was 6 min,and the material thickness was 6 mm.Under these conditions,the hardness of dried crabapple was 82.00 N,the brittleness was 8.00,the color difference was48.00,and the moisture content was 4 %.3.Three influencing factors(vacuum time,vacuum temperature,material thickness)were selected by single factor test.The optimal parameters of vacuum drying were determined by Box-Behnken response surface optimization test as follows : vacuum drying time 6 h,temperature61 °C,material thickness 6 mm.Under these conditions,the hardness of crabapple dry fruit was 83.00 N,the brittleness was 14.00,the color difference was 40.00,and the moisture content was 5 %.4.The texture characteristics,sensory quality,nutritional components and microstructure of dried crabapple fruit were compared under the best process conditions of the three drying methods.It was found that the dried crabapple fruit treated by vacuum drying had greater brittleness and moderate hardness than microwave and hot air drying.The comprehensive score of sensory evaluation was vacuum drying(84 points)> microwave drying(74 points)> hot air drying(70 points).The contents of nutrients(polyphenols,carbohydrates,protein,vitamin C,soluble solids and titratable acid)in dried crabapple fruit treated by vacuum drying were higher than those treated by microwave drying and hot air drying.The microstructure of vacuum dried crabapple fruit became loose and porous in the later stage,and the cell deformation was smaller,which was closer to the fresh sample.However,the cell structure of microwave dried and hot air dried crabapple fruit collapsed and contracted compared with vacuum drying.Therefore,the dried crabapple fruit obtained by vacuum drying has better quality. |
