方小明, 张晓琳, 王 军, 张 茜, 肖红伟, 刘嫣红, 巨浩羽, 梁 珊, 高振江. 荷花粉真空脉动干燥特性和干燥品质[J]. 农业工程学报, 2016, 32(10): 287-295. DOI: 10.11975/j.issn.1002-6819.2016.10.039
    引用本文: 方小明, 张晓琳, 王 军, 张 茜, 肖红伟, 刘嫣红, 巨浩羽, 梁 珊, 高振江. 荷花粉真空脉动干燥特性和干燥品质[J]. 农业工程学报, 2016, 32(10): 287-295. DOI: 10.11975/j.issn.1002-6819.2016.10.039
    Fang Xiaoming, Zhang Xiaolin, Wang Jun, Zhang Qian, Xiao Hongwei, Liu Yanhong, Ju Haoyu, Liang Shan, Gao Zhenjiang. Vacuum pulsed drying characteristics and quality of lotus pollen[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(10): 287-295. DOI: 10.11975/j.issn.1002-6819.2016.10.039
    Citation: Fang Xiaoming, Zhang Xiaolin, Wang Jun, Zhang Qian, Xiao Hongwei, Liu Yanhong, Ju Haoyu, Liang Shan, Gao Zhenjiang. Vacuum pulsed drying characteristics and quality of lotus pollen[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(10): 287-295. DOI: 10.11975/j.issn.1002-6819.2016.10.039

    荷花粉真空脉动干燥特性和干燥品质

    Vacuum pulsed drying characteristics and quality of lotus pollen

    • 摘要: 为了缩短花粉的干燥时间,保证干燥品质,将真空脉动干燥技术应用于干燥新鲜荷花粉,研究了真空保持时间(15、12、9、6和3 min)、干燥温度(45、50、55、60和65 ℃)对干燥动力学、水分有效扩散系数、干燥活化能的影响,并运用Weibull分布函数模拟了花粉真空脉动干燥特性曲线;此外还研究了真空保持时间、干燥温度对花粉蛋白质含量以及微观结构的影响,并对干燥前后的花粉进行了色差分析。试验结果表明:Weibull分布函数能够很好地描述花粉的真空脉动干燥过程,结合尺度参数、形状参数计算出花粉真空脉动干燥水分有效扩散系数在2.154 2×10-11 ~6.254 3×10-11 m2/s之间;干燥活化能为20.88 kJ/mol,表明新鲜荷花粉干燥每脱除1 kg水所需要的启动能量为1 160.00 kJ;试验参数范围内,随着真空保持时间的减少,干燥后花粉蛋白质质量分数呈现先增加后减少的趋势;当干燥温度为45 ℃,真空常压脉动比为12 min: 3 min时花粉蛋白质质量分数最高,为18.43%;扫描电镜结果显示,随着干燥温度的升高,花粉颗粒间致密程度降低,形成孔隙结构,这有助于干燥中水分的扩散迁移,花粉颗粒微观结构的完整性随着干燥温度的升高而降低;干燥前后花粉未发生色泽劣变。荷花粉真空脉动干燥的较佳参数为真空常压脉动比为12 min:3 min,干燥温度为45℃。研究结果为花粉真空脉动干燥技术的应用提供了理论依据和技术支持。

       

      Abstract: Pollen is the male reproductive material of plants and contains abundant nutrient substances, such as protein, polysaccharide and lipid of pollen, which are good for health-promoting. Drying is an essential processing step for pollen preservation since it can prevent the growth of microorganisms and decrease a lot of the moisture-mediated deteriorative reactions, and thus prolong the shelf-life of pollen. Currently, the traditional drying method for pollen is the natural sun drying, due to its low capital investments and operation simplicity. However, traditional natural sun drying possesses severe disadvantages, such as long drying time, rewetting or rotting caused by bad weather, contamination by dust and insects, non-uniform drying, and color deterioration due to long exposure to solar radiation. Furthermore, there are also some other drying technologies for pollen, such as hot air drying, vacuum freeze-drying and microwave drying. These drying methods all have some advantages and disadvantages which influence the drying rate and quality. Therefore, in order to improve the drying process and enhance the quality of pollen, the traditional drying technique should be replaced by more efficient, safer and more controllable industrial drying methods. Vacuum pulsed drying is a novel drying technology which can increase the drying rate and improve the product quality compared to traditional hot air drying. In current work, the vacuum pulsed drying technology was employed to dry lotus pollen and the effects of vacuum keeping time(15, 12, 9, 6, and 3 min) and drying temperature(45, 50, 55, 60, and 65 ℃) on the drying characteristics and quality of pollen were explored. It was found when the vacuum keeping time was 12 min, it obtained the least drying time. The drying time decreased with the increasing of drying temperature. The Weibull distribution model was applied to the drying process and the results were analyzed. The scale parameter α and shape parameter β were used to calculate moisture diffusion coefficient and drying activation energy. The results showed that the moisture diffusion coefficient varied from 2.154 2×10-11 m2/s to 6.254 3×10-11 m2/s, and the drying activation energy was 20.88 kJ/mol, which meant that removing 1 kg water needed about 1 160.00 kJ energy. In terms of dried quality, there was no color deterioration after vacuum pulsed drying. No significant change of b was found between the color of fresh pollen and dried pollen. It was found that the protein content of dried pollen initially increased and then decreased gradually with the decrease of vacuum keeping time. When the drying temperature was 45 ℃, and the pulsation ratio of vacuum keeping time to atmosphere keeping time was 12 min∶3 min, it obtained the most protein content of 18.43%. The vacuum keeping time and drying temperature all had significant influence on the protein of pollen. With the increasing of drying temperature, the microstructure became more porous which could significantly influence the texture. Larger number of pores and large pore size could enhance the moisture migration rate. It was also found that the integrity of pollen grain decreased with the increasing of drying temperature, for higher temperature caused more damage to the microstructure. The current work provides theoretical and technical reference for applying vacuum pulsed drying technology to pollen drying process.

       

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