Study On Lily Bulb Drying Based On Blanching Pretreatment Process Optimization

Fresh lily bulbs have high water content and are rich in nutrients such as flavonoids,phospholipids,proteins,polysaccharides,and saponins.If post-harvest treatments such as drying are not carried out in time after harvesting,browning and mildew will easily occur,seriously affecting their appearance and quality.nutrient content.In this paper,taking Hunan Longshan lily as raw material,by studying the browning of lily at different temperatures and blanching time,selecting the optimal blanching temperature and time range,analyzing the water diffusion law of lily bulbs in the process of infrared and hot air drying,revealing Its heat and mass transfer mechanism,and put forward a better drying process of lily,provide theoretical guidance for the processing guidance of lily and the research of related equipment.This research work includes the following contents:(1)Through the blanching pretreatment test of lily,the ideal pretreatment temperature of lily is 95℃ to 100℃,and the pretreatment time is about 4 to 7 minutes.When the temperature is lower than 95℃,the color of the lily will become dark brown after drying,which cannot achieve the effect of blanching pretreatment.Therefore,it is most effective and convenient to control the temperature at 100℃ and the time between 4min and 7min during blanching.(2)The drying rate of lily bulb by hot air is greatly affected by drying temperature.The drying rate of high temperature hot air is faster than that of low temperature hot air.Both drying temperature and blanching time have significant effects on the content of polyphenols and flavonoids in lily after drying.When the wind speed is constant at 2.5 m/s and the initial dry basis moisture content is 232%,the effective water diffusion coefficient of lily in the process of hot air drying at 60 to 90℃ after 4min,5min and 6min blanching pretreatment is 3.63×10-11m2/s-2.7×10-10m2/s.The drying activation energies of lily were 58.77KJ/mol,45.38KJ/mol and 24.75KJ/mol after blanching at 100℃ for 4min,5min and 6min,respectively.Considering the factors such as appearance quality and drying time,the hot air drying at a temperature of 70℃ is selected,and the drying time is 8 hours to obtain a highquality dried lily.(2)The drying rate of lily bulb first increased briefly and then gradually decreased during the whole infrared drying process.When the pretreatment time was the same,the drying time at 90℃ was more than 44.4%less than that at 60℃.Both drying temperature and blanching time had significant effects on the color of lily,as well as the content of polyphenols,flavonoids and starch after drying.When the initial dry basis moisture content is 232%,the effective moisture diffusion coefficient of lily in the infrared drying process from 60℃ to 90℃ after 4min,5min and 6min blanching pretreatment is 5.20×10-11m2/s～9.32×10-10m2/s,the drying activation energies of lily were 33.14KJ/mol,9.86KJ/mol and 7.04KJ/mol after blanching at 100℃ for 4min,5min and 6min,respectively.Based on the effects of drying temperature and blanching time on the quality of lily,the optimal infrared drying process for lily is obtained as follows:blanching in boiling water at 100℃ for 5 minutes,and infrared drying at 70℃ for 6 hours,which can maximize the drying rate and quality of dried lily.(4)Using the Modified Henderson and Pabis model can describe the process of hot air drying and infrared drying of lily.When infrared drying lily,its drying efficiency is higher than that of hot air drying.Under the same pretreatment conditions and drying temperature,the time required for infrared drying is reduced by more than 0.5 hours compared with the time required for hot air drying,and the activation energy required for drying is reduced.43.6%or more,the effective water diffusivity is increased by 43%,and the quality of the color parameters after drying is also better than that of hot air.