Study On Microwave Drying Characteristics And Process Optimization Of Fresh Ginger Slices

Ginger is widely used as a medicinal and edible herb in many countries because it is rich in many nutritional and medicinal substances.Fresh ginger contains more than90%water,microbial decay,water loss and shrinkage,cold damage,etc.lead to its short shelf life,drying is an effective way to extend its storage life.In this paper,the drying test was conducted using a drum microwave dryer with ginger as the research object.The drying characteristics of fresh ginger slices under different drying conditions were investigated using single-factor tests,mathematical models were established,energy efficiency analysis was conducted,and the effects of different drying conditions on the quality of ginger slices were further investigated,and finally the response surface optimization test was used to optimize the drum type microwave drying process for fresh ginger slices,and the results and conclusions of the study are as follows:（1）The drying process of ginger slices can be roughly divided into three stages:"rapid rise,slow decline,and rapid decline."The duration of the speed up stage is very short,and the main drying process is speed down drying;The higher the microwave power,the smaller the loading capacity,and the smaller the thickness of ginger slices,the greater the drying rate,and the shorter the drying time required.（2）The effective diffusion coefficient of water in the drying process of ginger slices increases with the increase of microwave power and thickness of ginger slices,but decreases with the increase of loading capacity;The drying efficiency increases with the increase of microwave power and loading,but decreases with the increase of ginger slice thickness;The unit energy consumption decreases with the increase of microwave power and loading capacity,and decreases with the increase of ginger slice thickness.The microwave power increased from 600W to 1800W,the effective water diffusion coefficient increased from 8.754150×10^-10 m²/s to 5.398393×10^-9m²/s,the drying efficiency increased from 26.46%to 40.56%,and the unit energy consumption decreased from 16.89 MJ/kg to 9.01 MJ/kg;The thickness of ginger slices increased from 1 mm to 7 mm,the effective water diffusion coefficient increased from 1.732592×10^-10 m²/s to 7.993228×10^-9 m²/s,the drying efficiency decreased from 43.31%to26.58%,and the unit energy consumption increased from 5.41 MJ/kg to 15.24 MJ/kg;The loading capacity increased from 200 g to 500 g,the effective water diffusion coefficient decreased from 6.241385×10^-9m²/s to 1.296911×10^-9m²/s,the drying efficiency increased from 30.05%to 42.43%,and the unit energy consumption decreased from 12.43 MJ/kg to 6.23 MJ/kg.It can be seen that increasing microwave power and loading capacity,reducing the thickness of ginger slices,can improve drying speed and efficiency,and reduce unit energy consumption.After fitting and analyzing nine thin layer drying mathematical models,it was found that Page model was the most suitable for describing the precipitation process of fresh ginger slices drying under different microwave power,and Midelli model was the most suitable for describing the precipitation process of fresh ginger slices drying under different loading amounts and ginger slice thickness.（3）With the increase of microwave power and loading,the total color difference?E and browning index BI of ginger slices first decreased and then increased,while the rehydration ratio,gingerol content,and ginger essential oil extraction first increased and then decreased;When the microwave power is 1200 W,the total color difference value?E and browning index BI values are smaller,respectively 17.39 and 86.00,and the loading capacity is 300g to 400g of ginger slices,the total color difference value?E and browning index BI values are lower;When the microwave power is 1200 W and the loading capacity is 350 g,the rehydration ratio of ginger slices is 3.19;When the microwave power was 1600 W and the loading capacity was 300 g,the gingerol content was higher,which was 2.52%and 2.86%,respectively;When the microwave power was 1000 W and the loading capacity was 300g,the extraction rate of ginger essential oil was 1.66%and 1.72%,respectively.As the thickness of ginger slices increased,the total color difference?E and browning index BI gradually increased,while the rehydration ratio,gingerol content,and ginger essential oil extraction first increased and then decreased;Ginger slices with a thickness of less than 4mm have a better color,with a total color difference?E of less than 17.30,and a browning index BI of less than 76.02;The thickness of ginger slices increased from 1 mm to 7 mm,the rehydration ratio decreased from 3.66 to 2.11,and the extraction rate of ginger essential oil decreased from 1.65%to 0.96%;When the thickness of ginger slices was 6 mm,the content of gingerol was the highest,2.79%;With the increase of microwave drying time,the total color difference?E and browning index BI of ginger slices gradually increased,the rehydration ratio and gingerol content first increased and then decreased,and the extraction rate of ginger essential oil gradually decreased.（4）In the process optimization of microwave drying of ginger slices,the Box-Behnken experimental design of the Design-Expert 13.0 data analysis software was used,with microwave power,loading capacity,and thickness of ginger slices as influencing factors,and drying efficiency,ginger rehydration ratio,gingerol content,and ginger essential oil extraction rate as inspection indicators.A response surface optimization experiment of three factors and three levels was conducted,Finally,the optimal microwave drying process conditions for fresh ginger slices were obtained as follows:microwave power 1256 W,loading capacity 355 g,and ginger slice thickness3.3 mm.