| Lycium Barbarum L.is a kind of characteristic agricultural products as a medicine and food source which has a high health and economical value.It is being planted largely in Ningxia,Xinjiang,etc in China.The moisture content of fresh Lycium Barbarum L.is about 80%,causing the difficulty for storage.Traditional Lycium Barbarum L.drying is natural drying,which needs a large drying area and long drying time,vulnerabled to weather,wind and birds and insects,poor sanitation.Due to the limitation of natural drying,the demand of mechanical drying of Lycium Barbarum L is growing.Our research group tried a various mechanical drying methods of Lycium,including hot air room drying,microwave drying,infrared drying and freeze drying,while this thesis focus on the infrared drying.The purpose of the research is to experimentally study the effect of the infrared drying process parameters on the product quality and optimize the infrared drying technology.The combined drying technology of infrared and other mechanical drying methods is also studied.The research resluts will lay a theoretical foundation for the development of mechanical drying equipment of Lycium.The main research contents and conclusions of this paper are as follows:(1)Color is an important indicator of dried Lycium products since the good color can attract the buying interest.A new method for quantitative characterization of the color of Lycium.was developed and was used in the infrared drying processing of Lycium.The varying trend of R was found to be positive correlation with the moisture content of the dried product.The R value of the dried product was stable in 20-30,and the R value was higher,the more red the Lycium.In the process of infrared drying,the Lycium’s color of the R value was fastest changing in the range of moisture content(wet base)between 0.73 and 0.74.(2)The optimization of medium-infrared drying process.The result of experiment showed that infrared wavelength of the peak absorption of Lycium was 2.927 m,9.780 m.A infrared drying experimental setup was developed and used in the infrared drying of Lycium.Experiemntal results showed that higher the drying temperature,the higher drying rate.The volume shrinkage rate and the content of polysaccharide are increased at first and then decreased;They reach the maximum value at 60 ℃.The color R and the hydration of the Lycium at 50℃ is optimal,and declining with the increasing temperature.When the drying temperature reaches 65 ℃,the surface of the Lycium is easy to form tiny bubbles,and this have a negative effect on the color of Lycium.The product quality of dried Lycium at 60 ℃ is considered to be excellent.(3)The combined drying technology of hot air and medium-infrared drying.In thiswork,it was found that the combination of medium-infrared drying and hot air drying can produce a good effect on the decreased drying rate,increased polysaccharide content,improved hydration and color.40 ℃ hot air drying for 6h-50℃ hot air drying for 3h-60 ℃ infrared drying for the end is the best drying way.(4)The comparison of infrared and microwave drying process.The experimental results showed that microwave heating had the advantages of fast drying,good water retention,high retention rate of polysaccharide,but microwave heating was not uniform,Lycium was easy to over heating The effect of microwave on the color of Lycium was not as good as that of the hot air drying on the R value,the higher the power of microwave,the lower the R value of the dried Lycium. |
