Dehydrated Blueberries by the Continuous Explosion-Puffing Process

A blueberry dehydration process which includes the unique continuous explosion-puffing system (CEPS) is described. A drying study including alternate drying pretreatments failed to increase the dehydration rate. It was found that care during processing was necessary to prevent rupture of the berries as rupture caused bleeding during drying which reduced the drying rate. Optimum operating conditions for CEPS were established for blueberries. Measurements of dried blueberry properties such as bulk density, color, rehydration, and disintegration were used to determine optimum operating conditions for pressure (103 kPa), temperature (190°C), and feed moisture (18.5%) for CEPS.     

胡萝卜脱水的动力学研究

讨论了几个变量对胡萝卜干燥速率的影响,并用不稳定状态扩散方程的标准解分析了降速干燥初始阶段的实验结果。尽管水分迁移机制比较复杂,用Fick定律预测脱水时样品温度与湿含量分布之间的关系仍具有精确性。     

胡萝卜片渗透脱水与真空油炸联合干燥动力学研究

为降低真空油炸果蔬脆片的脂肪含量,提高产品品质,本文研究了胡萝卜片渗透脱水与真空油炸联合干燥动力学,结果表明:随着渗透时间的延长,胡萝卜片的初始水分含量和平衡水分含量逐渐降低,脂肪含量、平衡脂肪含量以及脂肪的吸收速率也逐渐减少,皮尔逊积差相关分析显示:脂肪含量与其初始水分含量具有极显著的相关性(P<0.001);将渗透脱水Fick水分扩散规律和真空油炸一级反应动力学规律相结合,获得了胡萝卜片联合干燥过程中水分与脂肪含量变化的动力学方程,采用非线性回归法确定了方程系数,结果表明方程具有较高的决定系数,能够较好地预测渗透脱水与真空油炸联合干燥胡萝卜片水分和脂肪含量的变化。     

食品的介电特性在食品干燥过程中的在线无损检测技术

选用标准蔗糖、新鲜胡萝卜、葱、蘑菇和生菜为原料,研究干燥过程中原料电特性参数电容和水分含量的变化规律以及它们之间的相关性。结果表明60℃温度下热风干燥几种新鲜蔬菜,其水分含量随着干燥时间的延长而下降,到一定的水分含量后质量不再发生变化,电容的变化趋势与水分的变化相同,质量不变时电容也趋于恒定,两者之间存在极显著的线性正相关性,说明干燥过程中水分含量的测定可以用检测相对应点的电容值来计算,从而实现在线、无损监控食品干燥过程。     

添加胡萝卜纤维素对喷雾干燥荔枝果粉特性的影响

以胡萝卜纤维素作为干燥载体,采用单因素实验和正交实验设计,探讨不同载体添加比例、物料浓度、物料流量、热风温度等喷雾干燥工艺条件对荔枝果粉的含水量、堆积密度、吸湿性、分散性和感官属性等指标的影响。结果表明,荔枝果汁喷雾干燥优化的工艺参数:20 MPa压力下均质15 min,干燥载体胡萝卜纤维素和麦芽糊精添加量分别为15%和22.5%,果汁物料浓度为25%,物料流量为25 m L/min,物料温度为50℃,热风温度为175℃,样品的水分含量为3.24%,堆积密度为0.512 g/m L,吸湿性为0.038%,流动性为53.6°,分散性94 s,感官质量良好。      

Structural properties of dehydrated products during rehydration

The following structural properties of dehydrated apple, banana, carrot and potato were examined during rehydration: true density, apparent density, porosity and specific volume. Samples were dehydrated using five different drying methods: conventional, vacuum, freeze, microwave and osmotic; after which they were rehydrated in an air dryer at 50 °C and 80% air humidity. Structural properties were examined during rehydration to various moisture contents, ranging from 0.01 to 3.5 kg kg^–1 (dry basis). The dehydrated products did not recover their structural properties after rehydration as a result of structural damage that occurred during drying and the hysteresis phenomenon which took place during rehydration. Porosity of the rehydrated products was higher during rehydration than during dehydration. A generalized structural model was used to describe the structural properties, and of the four parameters that were incorporated, only the shrinkage coefficient, which represents volume expansion, changed on rehydration.     

柱状胡萝卜样品热风微波耦合干燥数学模型

利用热风微波耦合干燥装置研究了柱状胡萝卜样品的干燥特性,一个实验室规模的热风微波耦合干燥装置用来实现此实验目的。基于干燥过程中同时具有传热传质现象,建立了一个数学模型以此来预测干燥过程中样品内温度和含水量的分布。考虑到柱状样品的半径和微波的穿透深度,假定微波中的电场强度在样品内均匀分布。由于表面水分的蒸发而造成的热损失被考虑在内并将其作为模型的一个边界条件,利用数值方法中的隐式有限差分法对模型进行求解。通过干燥尺寸不同的柱状胡萝卜样品得到的实验值和模型的预测值进行比较来对模型进行验证,探讨了微波功率密度和热风温度的影响作用。      

胡萝卜热泵-远红外联合干燥工艺研究

采用热泵-远红外联合干燥工艺对胡萝卜片进行了干燥试验,研究了胡萝卜干燥预处理工艺、热泵干燥温度、远红外线辐射强度及联合干燥时间切换点对干燥速度、干燥能耗和类胡萝卜素损失率的影响。确定了胡萝卜热泵与远红外线联合干燥工艺的最佳工艺参数为:物料热烫时间120s,热泵干燥温度45℃,远红外热源辐射功率为2kW,热泵干燥与远红外切换点为物料含水率为50%。     

远红外真空干燥胡萝卜片过程中温度变化和模型

优化设计了果蔬远红外真空干燥设备,建立了胡萝卜片在远红外真空干燥过程中温度变化的数学模型,在自制设备上对模型进行了验证,反映了胡萝卜片远红外真空干燥的温度变化规律。     

Dehydration of carrots.

The effect of blanching, sulphiting, starching, freezing and sucrose and sodium
chloride dipping before air drying on moisture transport during carrot cube dehydration was studied. The results, interpreted in terms of existing theories combined with physical considerations, provide evidence that factors such as blanching, freezing and sucrose dipping affect moisture transport and product quality.     

Effect of simultaneous infrared dry-blanching and dehydration on quality characteristics of carrot slices

This study investigated the effects of various processing parameters on carrot slices exposed to infrared (IR) radiation heating for achieving simultaneous infrared dry-blanching and dehydration (SIRDBD). The investigated parameters were product surface temperature, slice thickness and processing time. A three-factor factorial design was conducted to determine the influence of processing parameters on moisture reduction, drying rate, residual peroxidase (POD) activities, surface color change and vitamin C retention. High surface temperature and/or thin slices had faster inactivation of enzymes and quicker moisture removal compared to the low surface temperature and/or thick slices. A Middili model performed well for describing drying behavior during the treatment, while a biphasic model and a quantic model fit well for describing the POD inactivation and the surface color change during the process, respectively. The process which produced 1 log reduction in POD activity has resulted in moisture reduction from 40.2 to 88.8 g/100 g, overall color change (ΔE) from 3.17 to 5.13 and retention of vitamin C from 56.92 to 77.34 g/100 g compared to control. It was concluded that SIRDBD could be used as an alternative to produce high quality blanched and partially dehydrated fruits and vegetables.     

甘蓝的新型组合干燥工艺

为了克服单一干燥造成的品质缺陷,提出了一种新型的组合干燥方式,以改善产品的外观品质和复水特性。以甘蓝为研究对象,主要探讨了组合干燥过程中热风温度、干燥转换点的物料含水率、微波强度、渗透处理对干燥特性的影响;并以成品色泽、复水比、Vc保留率为指标,对不同干燥方式获得的产品性能进行了比较。研究获得的组合干燥工艺参数为:70℃热风干燥至物料含水率60%,2.5 W/g微波强度下干燥至40%含水率,25℃下以2.8 g/mL料液比向半干产品中加入28%葡萄糖和15%NaCl混合渗透液处理15 min,最后70℃二次热风干燥至成品。产品的水分活度为0.466,含水量为16.34%,复水比为8.71,Vc保留率为31.05%。结果显示,组合干燥方式干燥速率快,能耗低,产品含有高水分含量、低水分活度,产品品质与真空冷冻干燥的产品相近,是一种工业化生产果蔬干制品的新方法。     

Drying Kinetics and β-Carotene Degradation in Carrot Undergoing Different Drying Processes

Superheated steam drying, which is an airless drying technology, has recently received much attention as an alternative to conventional hot air drying, which is a relatively oxygen‐rich drying process and causes much product quality degradation. However, because most food products are damaged when subjected to superheated steam at atmospheric or higher pressures, lowering the dryer operating pressure is preferred. In this study, the effects of a low‐pressure superheated steam drying (LPSSD), vacuum drying, and hot air drying on the drying and degradation kinetics of β‐carotene in carrot were investigated experimentally. LPSSD and vacuum drying led to less degradation of β‐carotene in carrot than in the case of hot air drying. The empirical models, which can describe the experimental data of β‐carotene degradation in carrot undergoing different drying techniques, were also proposed. β‐Carotene degradation in carrot depended more on the carrot temperature than its moisture content in all cases.     

胡萝卜片微波真空干燥动力学数值拟合

为了探索微波功率密度对产品微波真空干燥(MVD)的影响,本文在干燥特性的基础上,进行了胡萝卜微波真空干燥动力学方程的数值模拟,然后利用遗传算法进行胡萝卜多功率组合的微波真空干燥优化研究。结果表明,单一微波功率密度干燥下,微波功率密度越大,胡萝卜片干燥速率越大,干燥时间越短,产品越易焦糊;在4种常见的薄层干燥及其延伸模型的数值拟合对比研究中,发现基于wang延伸模型1(即MR=aexp(-ktⁿ)+c)能很好的表征不同功率密度下胡萝卜片微波真空干燥过程的脱水情况。进一步以三条(分别为20、5和0.6 W/g)不同微波功率密度下的胡萝卜干燥动力学方程为对象,通过遗传算法优化并获得了多功率密度连续微波真空干燥组合工艺参数;经验证,该工艺加工的胡萝卜片干基水分含量(0.078±0.005)g/g,没有焦糊;相比0.6 W/g单一微波功率的干燥结果,不但产品减少了收缩和焦糊现象,而且干燥效率提高了4.77倍。采用计算机遗传算法可以达到优化多功率组合的微波真空干燥加工工艺的目的,减少实验工作量,还可以获得计算机数值模拟模型,为实现微波干燥加工过程信息化提供技术支撑。     

2‐Furoylmethyl amino acids,hydroxymethylfurfural, carbohydrates and β‐carotene as quality markers of dehydrated carrots

BACKGROUND: Processing of vegetables in the food industry usually includes dehydration as a preservation process. Industrial convective air drying of carrot can involve steam blanching of the raw product after peeling and cutting, and different stages of dehydration (first space, second space and final drying). Although the shelf‐life of carrot is significantly extended, important changes in its chemical composition can take place during dehydration since high temperatures and long times are used. This research is a preliminary study to evaluate the usefulness of β‐carotene, carbohydrates, hydroxymethylfurfural (HMF) and 2‐furoylmethyl amino acids (2‐FM‐AA) as quality markers of dehydrated carrots. RESULTS: A considerable decrease in β‐carotene and reducing carbohydrates was observed during dehydration. HMF, absent in raw carrots, increased during the whole drying process and the highest formation was found during the steam blanching stage. 2‐FM‐AA of lysine, arginine, γ‐aminobutyric acid and alanine were progressively originated up to the second space and decreased during the final drying. CONCLUSION: The combined use of HMF and 2‐FM‐AA seems to be advantageous for the assessment of the optimal processing conditions to obtain high‐quality dehydrated carrots. Copyright © 2008 Society of Chemical Industry     

Effects of microwave and infrared drying on the quality of carrot and garlic

The effects of microwave and infrared drying on the quality of carrot and garlic were studied and compared with the effects of conventional hot air (tray drier for carrot and fluid bed drier for garlic) drying. The quality of carrot and garlic were evaluated by instrumental and sensory analysis. Rehydration, moisture content, water activity, particle density, bulk density, porosity and colour values were obtained for microwave, infrared and hot-air dried vegetables. In addition, total moisture content versus time was represented by drying rate curves of carrot and garlic samples. Finally, free moisture content versus drying rate were compared for the three different drying methods.     

酶解生产微胶囊胡萝卜速溶粉工艺研究

胡萝卜在我国大部分省市均有种植,其β-胡萝卜素、维生素、矿物质含量丰富。本文利用微胶囊技术将经酶解处理的胡萝卜加工成一种速溶产品。利用液态果胶酶PectinexUltraSP-L和PectinexSMASHXXL酶解胡萝卜浆,提高了胡萝卜汁的产量。结果表明,果胶酶PectinexUltraSP-L最佳用量(以胡萝卜浆重量计)为0.09ml/kg胡萝卜浆液,PectinexSMASHXXL最佳用量0.18ml/kg胡萝卜浆液,最佳温度50℃,酶解时间2h,酶处理后出汁率能提高到82.8%。加入15%玉米油,3%乳化剂,3%酪朊酸钠和40%糊精微胶囊化后喷雾干燥得到胡萝卜速溶粉。该产品既能直接加水冲调饮用,也能作用一种成分加入到其它配方食品中,应用范围得到了进一步的扩大。     

MATHEMATICAL MODELLING of MOISTURE, VOLUME and TEMPERATURE CHANGES DURING DRYING of PRETREATED APRICOTS

Simultaneous heat and mass transport in dehydration of apricots is presented. the moisture variation of apricots, pretreated with various combinations of sodium-meta-bisulphite and ethyl oleate solutions, was analyzed by Exponential and Page equations. Use of ethyl oleate in addition to sodium-meta—bisulphite as a pretreatment solution was observed to decrease drying times of apricots. the system of differential equations determining the unsteady-state temperature distribution was solved. Thermophysical properties were taken to be moisture dependent. the variation of volume upon drying (shrinkage) was introduced into the solution by taking space intervals to be variable in the apricot side while they were taken to be constants in the stone side. the dominant mass transfer mechanism was diffusion while diffusivity of water changed depending upon the pretreatment solution. Comparison between predicted and experimental data shows good agreement for both moisture and temperature variation of the apricots throughout the drying process.     

Effect of Osmotic Dehydration and Air Drying on Physicochemical Properties of Dried Kiwifruit and Modeling of Dehydration Process Using Neural Network and Genetic Algorithm

In this study, effect of osmotic dehydration and hot air-drying conditions on shrinkage, rehydration capacity, and moisture content of dried kiwifruit was investigated and artificial neural network and genetic algorithm were applied as an intelligent modeling system to predict these physicochemical properties. Kiwifruit slices were immersed in osmotic solutions (30%, 40%, 50%, and 60%) at different temperatures (20, 40, and 60 °C) and were dried at 60, 70, and 80 °C for 5, 6, and 7 h. The results showed that increasing drying time and temperature caused an increase in shrinkage, while rehydration capacity and moisture content were decreased. Neural network model with one hidden layer, four inputs (operating conditions) was developed to predict three outputs (shrinkage, rehydration capacity as a well as moisture content) and genetic algorithm was used to optimize network structure and learning parameters. Artificial neural network models were then tested against an independent dataset and results showed the ability of optimized intelligent model to estimate shrinkage, rehydration capacity, and moisture content with high correlation coefficients (0.94, 0.93, and 0.96, respectively). Moreover, sensitivity analysis indicated that the most sensitive input variable toward such predictions was drying time.     

Fixed and Incremental Levels of Microwave Power Application on Drying Grapes under Vacuum

ABSTRACT: Microwave vacuum drying has been investigated as promising potential for high-quality dried fruits. In this study, a batch microwave vacuum dryer was used to understand the effect of levels of microwave power on the drying characteristics and moisture content of grapes. Thompson seedless grapes were treated 1st for 30, 60, and 90 min at fixed levels of 500, 750,1000,1250, and 1500 W at a reduced pressure of 2.7 kPa and then treated by 3 staged microwave power levels: a higher level of power during the initial stages of dehydration and 2 subsequently lower levels of power applied as the moisture content decreased. A typical temperature profile was found during the drying process, linearly increasing at the start of drying, followed by a nearly constant value during the drying period while water was evaporating. The total specific energy estimated by the energy balance model was 0.97 to 1.01 W-h/g of fresh grapes and agreed well with the experimental specific energy of 0.85 to 0.90 W-h/g for the fixed power tests. The multiple regression results showed that the specific energy was the most influential parameter on the final moisture content of grapes both in fixed and incremental power levels. Further research is needed to further improve the process with high efficiency and good product quality using product temperature as a control measure. Keywords: microwave vacuum dehydration, specific energy, fruits, grapes