[关键词]
[摘要]
目的 探索恒定相对湿度及阶段降湿对西洋参Panacis Quinquefolii Radix根干燥特性和品质的影响,为提高西洋参根干燥效率和干燥品质提供依据。方法 研究干燥温度为55℃条件下,恒定相对湿度(20%、30%、40%)、阶段降湿40%分别保持1、5、9 h后降为20%及连续排湿干燥条件下对西洋参干燥特性、水分有效扩散系数(Deff)、复水比、收缩比、总皂苷含量及微观结构的影响。结果 恒定相对湿度干燥条件下,相对湿度越低干燥速率越大,相对湿度为20%时比40%时干燥时间缩短了6.8%;阶段降湿干燥条件下,相对湿度40%保持5 h后降为20%相对于连续排湿干燥方式,干燥时间缩短了3.4%,干燥过程出现短暂的升速阶段;水分Deff在1.49×10-10~2.50×10-10 m2/s;复水性主要受物料细胞结构的破坏程度及复水前含水率的影响,且随相对湿度的增大而减小,收缩比随相对湿度的增加而增大,高湿有利于总皂苷含量的保留和转化;微观结构观察结果显示,连续排湿干燥时西洋参根表面结壳硬化,故导致干燥时间延长、复水性降低;阶段降湿干燥有助于西洋参根形成水分子迁移扩散孔道,从而缩短干燥时间,提高复水比;相对湿度40%保持5h而后降为20%时,综合评分最高为0.61±0.01,为最优干燥工艺,此时复水比为2.23±0.12、收缩比为0.26±0.06、总皂苷质量分数为(5.01±0.04)%。结论 阶段降湿干燥方式可提高西洋参根的干燥效率和干燥品质,为热风干燥西洋参根过程中如何调控相对湿度提供理论依据和技术支持。
[Key word]
[Abstract]
Objective Taking Panacis Quinquefolii Radix (PQR) as study object, the drying characteristic and quality was investigated under constant relative humidity (RH) and step-down RH drying method in order to provide foundation for improving drying efficient and quality of PQR. Methods At drying temperature 55℃, the effect of constant RH (20%, 30%, and 40%), step-down RH, when RH 40% was kept for 1, 5, and 9 h and then decreased to 20%, and continuously dehumidification drying conditions on drying characteristic, moisture effective diffusion coefficient, rehydration ratio, shrinkage ratio, total ginsenoside content and microstructure were investigated. Results With constant RH drying condition, the lower the RH was, the higher the drying rate was. When RH was 20%, the drying time was shortened by 6.8% compared with RH of 40%. With step-down RH drying condition, when RH 40% was held for 5 h and then decreased to 20%, the drying time was shortened by 3.4% compared with dehumidification drying method. Also, a transient increasing drying rate phase was appeared. Moisture effective diffusion coefficient ranged from 1.49×10-10 to 2.50×10-10 m2/s. Rehydration ratio mainly depended on the damage degree of the PQR cellular structure and the moisture content before rehydrating. Additionally, the rehydration ratio and shrinkage ratio increased with the increase of RH. High RH was benefit for reserving and transferring of ginsenoside content. The microstructure results showed that under continuous dehumidification drying process, the PQR surface was crusted so that the drying time was prolonged and rehydration ratio was decreased. On the other hand, step-down RH drying method was benefit for porous structure formation, which was helpful for shortening drying time and improving rehydration ratio. When RH 40% was kept for 5 h and then decreased to 20%, the comprehensive score of this drying condition achieved its maximum value as (0.61±0.01). Such drying condition was regarded as the best drying process with the rehydration ratio, shrinkage ratio and total ginsenoside content of 2.23±0.12, 0.26±0.06, and (5.01±0.04)%, respectively. Conclusion Step-down RH drying method can improve PQR drying efficient and quality and such conclusion provided theoretical foundation and technical support for how to adjust RH during hot air drying of PQR.
[中图分类号]
R283.3
[基金项目]
农业部现代农业产业体系中药材加工机械化(CARS-21);即食太行鸡鸡肉制品加工关键技术研究与示范(18227118D);河北经贸大学科研基金国家课题培育项目(2018PY15)