Study On Hot Air Drying Characteristics Of Yam

Yam is popular among people because of its great nutritional value,and it can be used both as a vegetable and as a health food.However,the water content of yam is high,and the harvest season of yam is concentrated,which is not suitable for storage.Therefore,it is of great significance to study the drying of yam.The drying of yam mostly stays in the study of hot air drying at constant temperature.In this paper,the constant temperature hot air drying test and variable temperature hot air drying test were carried out on the test bench.The slice thickness of yam was set at 5 mm.Under the condition of constant temperature drying,the characteristics of hot air drying with different constant temperature(45??50??65?)and hot air velocity(0.4m/s?0.7m/s?1.0m/s)were studied.Under the condition of variable temperature hot air drying,the drying characteristics of variable temperature hot-air drying were studied in the range of(40?-60??45?-65??50?-65?).By comparing the drying time,drying rate,rehydration rate,drying energy consumption and quality of yam under two drying methods,it is concluded that the drying time of variable temperature drying is a little longer than that of constant temperature drying,but the energy consumption of variable temperature drying is less than that of constant temperature drying,and the quality of yam is lower than that of constant temperature drying.About the quality of yam after drying,a series of problems appeared in constant temperature drying,such as blackening phenomenon,drying shrinkage phenomenon and hardening phenomenon,which is greatly improved by using variable temperature drying.And variable temperature drying is better than constant temperature drying in rehydration rate.Summarize the test data and analyze,the conclusion of the experiment is as follows: When the slice thickness is 5mm,and the wind speed is 0.7 m/s,the optimum temperature range is from 45? to 65?,and the rising temperature is 2? per hour.By summarizing and arranging the test data of yam hot air drying at variable temperature,a mathematical model-page model,which is suitable for hot air drying of yam,has been established.It can provide a theoretical basis for the drying process and batch production of yam by changing temperature and hot air.The time required for drying can be calculated from the allowed safe storage moisture content of Chinese yam.It can avoid the adverse effects of long drying time and too short drying time on the quality of Chinese yam,and can reduce the number of experiments in the actual drying process,and avoid the waste of energy and resources.