【作者】 安可婧；

【导师】 汪政富； 胡小松；

【作者基本信息】 中国农业大学 ， 农产品加工及贮藏工程， 2014， 博士

【摘要】 本文以生姜为原料,采取间歇式以及变功率实现微波均匀化目的,筛选出时间短、能耗小、产品品质高的热风间歇微波耦合干燥(AD&IM),并结合多种前处理(渗透脱水、超高压、二氧化碳浸渍)与AD&IM进行联合干燥,进一步提高干燥产品品质、减小能耗,从而探索出一种高效、节能、保质的新工艺。论文主要结论如下：(1)选取热风干燥、红外干燥、冷冻干燥、微波干燥以及AD&IM进行干燥时间、能耗和品质的对比。结果表明,相比其他几种干燥方式,AD&IM的干燥时间短,能耗小,对6-姜酚、8-姜酚、10-姜酚具有较好的保留作用,其提取物清除DPPH-和ABTS·力最强。因此,选择AD&IM作为最佳干燥方式进行后续研究。(2)采用常压渗透、超声渗透以及真空渗透等前处理方式与AD&IM进行联合干燥。结果表明：相比直接AD&IM干燥,渗透处理使生姜干燥速率降低,而使干燥产品品质提高。常压渗透和脉冲真空渗透提高了干燥样品的复水性。渗透处理后干燥样品的姜酚、姜烯酚含量显著高于直接干燥样品,其中脉冲真空渗透的样品中各姜酚、姜烯酚含量最高。脉冲真空渗透处理对干燥生姜的挥发性成分具有保护作用。(3)采用超高压、冷冻结合超高压、热烫、冷冻等物理方式与AD&IM进行联合干燥。结果表明：高压500MPa处理后干燥样品的DPPH-清除能力、Fe3+还原能力以及ABTS-清除能力最强,显著高于未经高压处理的样品。高压处理后生姜干燥速率显著提高,其中,冷冻结合100MPa、500MPa、热烫处理以及冷处理后样品的干燥时间分别缩短了30%、20%、25%和10%。冷冻结合250MPa和冷冻结合100MPa处理后干燥样品的挥发性成分与鲜姜的最相似。(4)采用一种新型绿色环保的前处理方式——二氧化碳浸渍(Carbonica Maceration,CM)与AD&IM进行联合干燥。CM可以改变细胞的通透性,引发厌氧呼吸,对生姜干燥品质和干燥时间具有积极的影响。结果表明：CM处理后生姜干燥时间显著缩短,其中CM2(0.2MPa、40℃、10h)处理后样品干燥时间可缩短35%。CM处理后干燥样品中各姜酚含量显著升高。其中,CM4(0.2MPa、30℃、10h)处理后6-姜酚、8-姜酚、10-姜酚、6-姜烯酚含量分别是直接干燥样品的2.49倍、1.45倍、1.45倍、1.36倍。综合干燥速率以及姜酚含量、颜色、复水性等品质指标,认为CM2处理联合AD&IM为最优的生姜干燥工艺。(5)本文基于Lambert微波能量吸收定律以及Fick传质第二定律首次建立了一维平板数学模型来预测AD&IM干燥过程中水分和温度的变化规律,模型的相对偏差在10%以内,说明模型可以较好地模拟实际干燥过程,为AD&IM干燥过程的优化和自动控制提供了有效手段。更多还原

【Abstract】 Hot air coupling microwave (AD&IM) drying was adopted for ginger drying, in the meanwhile intermittent and varied power microwave was used to make microwave more homogeneous. Different pre-treatments (osmotic dehydration, high pressure, carbon dioxide maceration) was combined with AD&IM in order to find out the most suitable, efficient, energy saving and best quality preserved approach for ginger drying. The main results and conclusions are as follows:(1) Hot air drying, infrared drying, freezing drying, microwave drying and AD&IM drying were selected to conduct the comparison of drying energy consumption, drying time and quality preserved of dried ginger slices. The results showed that AD&IM drying played an excellent role in retaining6-gingerol,8-gingerol and10-gingerol content as well as its merits of shorter drying time and lower energy consumption. The extract of ginger dried by AD&IM yields the best scavenging ability of DPPH· and ABTS·.(2) The osmosis effectively inhibited enzymatic browning reactions, and had a good protection for color and phenolic compounds of ginger. Dried samples after constant pressure osmosis and pulsed vacuum osmosis had a better rehydration ratio than samples directly dried by AD&IM. Gingerol, shogaol and zingiberone of dried samples pretreated by pulsed vacuum osmosis were significantly higher than those of ginger directly dried by AD&IM. Volatiles of fresh ginger were more similar to those of dried samples with pulsed vacuum osmosis, which suggested that volatile components of dried gingers could be preserved the when pulsed vacuum osmosis was applied.(3) Dried gingers after500MPa high-pressure pretreatment yielded the best scavenging capability of DPPH-and ABTS-as well as Fe3+reducing ability, significantly higher than samples without high pressure processing. Dried ginger with blanching pretreatment ran the second place while dried samples with freeze combing high pressure treatment turned out to be much weaker in terms of above abilities. The drying rate of ginger after high pressure pretreatment was significantly increased, the drying time of dried samples with freeze combing100MPa,500MPa, blanching and freeze pretreatments were shorten by30%、20%、25%and10%, respectively, compared with dried samples without pretreatments. The fresh samples had more similar volatile components with dried samples pretreated by freeze combining with250MPa and100MPa.(4) A new environmental friendly pretreatment was studied, namely Carbonica Maceration (CM). Carbon dioxide can change the permeability of the cell and trigger the anaerobic respiration, which had positive effect on dynamics of AD&IM drying and quality of dried gingers.CM pretreatments can significantly reduced the drying time.The drying time of ginger pretreated by CM2(0.2MPa,40℃,10h) was reduced by35%.In the meanwhile, CM pretreatment significantly improved the content of gingerol and shogaol of dried ginger.The highest gingerol content was found in CM4(0.2MPa,30℃,10h) pretreated samples and its6-gingerol,8-gingerol,10-gingerol and6-shogaol content were2.49,1.45,1.45and1.36times, respectively, of AD&IM dried samples. Dried gingers with CM pretreatment had much smaller colour change with fresh samples, so CM had very good protection for the color of dried samples.(5) Based on the Lambert law of microwave energy absorption and the second Fick law of mass transfer, one-dimensional planar mathematical models were established to predict the moisture and temperature distribution of ginger during hot air coupling with microwave drying.The relative deviations of models were within10%, suggesting models can well simulate the actual AD&IM drying process of ginger. The models can provide effective means for process optimization and automatic control for AD&IM in production application.更多还原