| Lilium has high edible and medicinal value because of an abundantnutrients and biologically active substances.Dryingcan prevent the lily bulb from browning,extend the storage periodand increase the added value.In order to improve the quality of dried lily products,this paper compares the effects of different drying methods on the quality of lilybulbs,studies the microwave vacuum drying characteristics,establishes drying kinetic modelsand optimizes the drying process.The main conclusions are as follows:1.The effects of hot air drying,far infrared drying,vacuum freeze drying,microwave vacuum drying,vacuum drying and sun drying on the quality of lily bulbs were studied.The results showed that the microwave vacuum dried lily bulbs had moderate hardness and the shortest drying time;microwave vacuum dried lily powder had good gelatinization stability,and was not easy to age.Thecolor of vacuum freeze-dried lily bulb and microwave vacuum dried lily bulbwere closest to the color of fresh samples and the rehydration rates of the two were higher.Vacuum freeze-driedlily bulbs and microwave vacuum dried lily bulbs had the highest retention rate of biologically active ingredients,and microwave vacuum dried samples had the highest clearance rate for ABTS free radicals.Vacuum freeze-dried lily bulbs had the highestorderof starch granule surface structure,with the highest crystallinity of25.10%±0.73%.Vacuum freezedried and microwave vacuum dried samples had the highest comprehensive evaluation scores,butthe vacuum freeze-dried lily bulbs had low hardness and dried with long time,so microwave vacuum dryingis an ideal drying method for lily bulbs.2.The effects of different microwave power,vacuum degree,rotation speed and temperature on the dried characteristics of lily bulbs were studied,and the microwave vacuum drying kinetic model of lily bulbs was established.The results showed thatmicrowave power,vacuum degree and temperature all hadsignificant effects on the microwave vacuum driedlily bulb characteristics(P<0.05).The higher the microwave power,the vacuum degree andthe temperature,the faster the drying rate;the rotation speed did notaffect thecharacteristics significantly(P>0.05);Page equation model had the highest fitting degree,and could accurately predictthe microwave vacuum drying process of lily bulbs.Deffranged from 1.63×10-8 m2/s to 5.43×10-8 m2/sunder different conditions,andincreased with the increase of temperature,microwave power,vacuum degree.The value of activation energy(Ea)at different drying temperatures was 17.847 k J/mol.3.The process optimization test results showed that the significanceof each regression model was goodand the misfit was not significant;the optimal drying process is:microwave power 600 W,vacuum degree-0.09 Mpa,temperature 50?55?.Under the conditions,the color,rehydration rate and total saponin content were 66.24±0.41(whiteness),161.87±3.23% and 0.658±0.014 mg/g. |
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