摘要
为了提高切片茄子的干制品质、缩短干燥时间,对热风干燥前的切片茄子进行了乙醇浸渍处理。以不同干燥温度(45、55、65℃)、预处理乙醇体积分数(0、5%、15%)和茄子切片厚度(1.0、1.5、2.0 cm)为试验因素,以干燥时间及干燥后产品的干燥速率、色泽、复水比和微观结构为评价指标进行正交试验。试验结果表明:干燥温度、乙醇体积分数和切片厚度对干燥时间均有显著影响(P〈0.05);综合评价的影响顺序由大到小依次为:切片厚度〉干燥温度〉乙醇体积分数;切片茄子的干燥过程属于降速干燥,通过费克第二定律得到切片茄子的水分有效扩散系数在2.74×10^-9~7.75×10^-9 m^2/s;切片厚度对干燥后茄子片的复水比有显著影响(P〈0.05),复水比随着切片厚度的增加而减少;乙醇体积分数对干燥后茄子片的色泽具有显著影响(P〈0.05),而且可以改变干燥后茄子的微观结构改善物料外观品质。当乙醇体积分数为15%、干燥温度为65℃、切片厚度为1.0 cm时,干燥时间为225 min,复水比为4.93,明亮度为88.24,既有较快的干燥速率又能够得到比较好的色泽。研究表明适宜体积分数的乙醇浸渍预处理能够提高切片茄子的干燥速率、改善色泽,为高品质切片茄子快速干燥提供了理论依据。
Because the eggplant is widely planted all over the country, but the moisture content of fresh eggplant is high and the shelf life is short, so harvested eggplants should be dried and dehydrated in time. How to achieve high-quality dried products is one of the important directions in drying research. Chemical impregnation process is a novel pretreatment technology, and ethanol is chosen as a chemical, which has many advantages, such as fast penetration, easy to evaporate, no chemical residues and harmless to human body, and has been applied to the pretreatment of fruit and vegetable. In order to improve the drying quality of eggplant slices and shorten the drying time, the eggplant slices were dipped in ethanol before hot air drying. The effects of different drying temperature(45, 55 and 65℃), ethanol concentration(0, 5% and 15%) in pretreatment and slice thickness(1.0, 1.5 and 2.0 cm) on drying rate, color, rehydration ratio and microscopic structure were investigated through the orthogonal experiments in this paper. Results showed that drying temperature, ethanol concentration in pretreatment and sample thickness had significant(P〈0.05) effects on the drying processing. In addition, the sample thickness was most significant, followed by drying temperature and ethanol concentration in pretreatment. The drying time decreased with the increase of temperature, increased with the increase of slice thickness of the eggplant, and decreased first and then increased with the increase of alcohol concentration in pretreatment. The whole drying process was a kind of falling-rate drying. According to Fick's Second Law, the water effective diffusion coefficient was determined, which ranged from 2.74×10^-9 to 7.75×10^-9 m^2/s. The sample thickness had greater impact(P〈0.05) on the rehydration ratio compared with the drying temperature and ethanol concentration, and the rehydration ratio decreased as the sample thickness increased. The ethanol concentration in pretreatment had important influence(P〈0.05) on color parameters of dried eggplant slices, but the effects of eggplant thickness and drying temperature on the color and lustre were not significant, which were far less than that of ethanol concentration in pretreatment on the color and lustre. And the pretreatment with ethanol also could change the microstructure and appearance quality of the dried samples. After eggplant was dipped in ethanol with low concentration, its moisture would be faster evaporated and the internal free water would be sent out in the drying process, and the drying rate was improved. And after eggplant was impregnated with high-concentration ethanol, ethanol made eggplant's internal nutrient composition change, which resulted in its structure more compact, and prevented moisture migration in the process of drying. Taking account of the drying rate and quality attributes, drying at 55℃, with ethanol concentration of 15% and sample thickness of 1.5 cm were recommended as the most favorable conditions for eggplant slice drying. In this drying condition, drying time, rehydration ratio and lightness was 225 min, 4.93 and 88.24, respectively. The present findings indicate that ethanol dipping pretreatment can not only enhance drying rate but also improve color attributes of dried products. The results provide a theoretical reference for the rapid drying of high-quality eggplant slices.
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2016年第9期233-240,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(31501548
31360399
31201436)
国家科技支撑项目(2015BAD19B010201)
关键词
干燥
优化
品质控制
切片茄子
乙醇浸渍
复水比
色泽
微观结构
drying
optimization
quality control
eggplant slice
ethanol dipping pretreatment
rehydration ratio
color parameters
microstructure