八角热风干燥水分变化及品质分析

Moisture Transformation and Quality Analysis of Star anise During Hot Air Drying

为了探究八角的干燥特性及内部水分扩散机理,本研究以热风温度(50、60和70℃)和预处理方式(杀青和不杀青)为实验变量,对八角进行了热风干燥实验,同时进行低场核磁共振检测和品质分析。结果表明,八角干燥过程基本处于降速干燥阶段,且干燥时间与热风温度呈负相关关系,杀青处理可以降低干燥时间。经低场核磁共振T_(2)谱检测,发现新鲜八角含有3个波峰,经干燥加工处理,不易流动水峰会分离出来1~2种波峰,这部分增加的波峰为大分子有机物。通过对八角干燥过程中的各峰面积和各组分占比进行研究,发现干燥加工主要除去的水分为不易流动水,而结合水、大分子有机物和小分子有机物的质量变化很小。杀青预处理对干燥过程八角的波峰分布影响甚微,但增加了八角的干燥速率。通过对八角品质的分析可以得到:经杀青预处理,干燥后的八角色泽更好,复水能力更强,但皱缩率更大,且热风温度越高,八角的复水能力越大,但会导致皱缩率也增大。

To explore the drying characteristics and the moisture diffusion mechanism in drying process of the Star anise,the hot-air experiment and low-field nuclear magnetic resonance(LF-NMR)of the Star anise were carried out and the quality of dryed Star anise were analyzed,where the experimental variables were drying temperature(50,60 and 70℃)and pretreatment(blanching).The results showed that the drying process was basically in the falling rate period.The drying time was negatively correlated with the drying temperature of the hot air,and the blanching process could reduce the drying time.Three peaks were found in the fresh Star anise through low-field nuclear magnetic resonance.Through the drying process,it was found that 1~2 kinds of peaks could be separated from the water peak which was not easy to flow,and those were macromolecular organic matter.According to the area of each peak and the proportion of each component,most of the water removed from the Star anise in the drying process was non-flowing water,and there was a small change in the mass of the bound water,macromolecular organic matter and small molecule organic matter changed little.The pretreatment had little effects on the peak distribution of Star anise during the drying process,but the drying speed could be shortened.The quality of Star anise was showed that the dried Star anise was brighter in color,stronger in the rehydration rate,but greater in shrinkage rate after blanching.And the higher the hot air temperature was,the higher rehydration rate but higher shrinkage rate the dried Star anise had.