微波真空干燥胡萝卜片过程中收缩变形的数学模型研究

研究胡萝卜片微波真空干燥过程中物料的收缩变形,利用正交试验,得出各因素对胡萝卜片干燥变形的影响程度大小及因素之间的相互影响关系,通过数学回归,得到胡萝卜片微波真空干燥过程收缩变形的数学模型方程,并对方程的显著性检验以及参数进行了综合优化,提出了胡萝卜收缩变形较小的微波真空干燥工艺参数的最佳组合.     

Modelling of dehydration-rehydration of orange slices in combined microwave/air drying

The development of new citrus products, such as dry products for direct use or for rehydration, is interesting to promote their consumption. Combined microwaves (MW)–air (2 m/s, 60 °C) drying of orange slices has been studied in terms of process kinetics and of the rehydration capability as affected by the applied MW power (0, 0.17, 0.36, 0.69 and 0.88 W/g). Drying curves were modelled considering two periods, with different kinetic constants, related with the effective water diffusivity. These constants increased linearly with the applied MW power and, despite the low levels of MW power used, a sharp reduction in drying time of orange slices was obtained. Rehydration behaviour of orange slices was modelled through Peleg's and Weibull's equations. No differences in rehydrating behaviour were observed as a function of the applied MW power. So, the highest level, which was limited to avoid sample browning, will be recommended to reduce the drying time.     

Ultrasound as pretreatment for drying garlic slices in microwave and convective dryer

Food Science and Biotechnology - The effects of ultrasound pretreatment (US) before hot air drying (HAD) and microwave drying (MWD) of garlic slices were investigated. For this aim ultrasonic bath...     

猕猴桃片冻干—真空微波联合干燥过程中品质变化及收缩模型

以猕猴桃为原材料,利用冻干—真空微波联合干燥的方式,选取不同的微波功率(0.25,0.30,0.39 W/g),结合猕猴桃在干燥过程中的收缩比、感官品质、色差、复水比、孔隙率等,分析猕猴桃片在干燥过程中的干燥特性、孔隙结构和收缩特性,建立猕猴桃片冻干—真空微波干燥过程中的收缩模型。研究结果表明,不同微波功率下,猕猴桃片的干燥特性有很大差异,微波功率越大,猕猴桃片的感官评分越高,色差越小,复水比越大,收缩比也越大,即达到干燥终点的体积越大,且猕猴桃片的孔隙率也越大。随着干燥的进行,猕猴桃片的水分含量越低,收缩比越小。猕猴桃片的最佳收缩模型为SR=k_1+k_2MR+k_3(MR)~2,R~20.99,RSS0.001,能很好地反映猕猴桃片在冻干—真空微波联合干燥过程中体积收缩的变化。     

Kinetics of colour change of bamboo shoot slices during microwave drying

The effect of microwave power on colour change kinetics of bamboo shoot slices was investigated during microwave drying. Colour changes were quantified by tri‐stimulus Hunter L (whiteness/darkness), a (redness/greenness), and b (yellowness/blueness) system. These values were also used for calculation of total colour change (ΔE), chroma, hue angle, and browning index (BI). Microwave drying as expected changed colour parameters because of browning. The values of L and b decreased, while values of a and ΔE increased during drying. Mathematical modelling of colour change kinetics indicated that L, b, chroma and BI could be defined using a first‐order kinetic model, while a, ΔE and hue angle could be defined using a zero‐order kinetic model. Considering together colour deterioration and quality of dried bamboo shoot slices at higher power reveals the need of process standardisation for getting good quality product.     

微波功率对月柿果片微波间歇干燥中水分迁移及品质的影响

目的：探讨微波间歇干燥对月柿果片水分动态和微观结构的影响。方法：选取不同微波功率（280,350,420,490,560 W）对月柿果片进行微波间歇干燥,对干燥过程中月柿果片的水分动态和迁移进行监测,以及对月柿果片的色泽、质构、微观结构进行测定分析。结果：新鲜月柿中的水分主要以结合水（T₂₁）、不易移动水（T₂₂）和自由水（T₂₃）3种形式存在,分别对应3个明显的水峰。随着干燥时间的延长,不易移动水和自由水的横向弛豫时间显著降低。L^*、a^*、b^*值随着微波功率的增加显著减小,ΔE、硬度、弹性、咀嚼性随着微波功率的增加而增加。随着微波功率的增加,果片的组织结构收缩塌陷越明显。结论：较低的微波功率能得到品质较佳的月柿干制品。     

大蒜片真空微波干燥模型的建立

为探索出不同真空微波条件对大蒜片干燥速率的影响,选取微波功率Q、负载量m、真空度Pw等因素,范围分别在50～150W、80～140 g、0.07～0.09MPa,以干燥速率为指标在切片厚度3 mm条件下进行试验.试验结果表明:大蒜片的真空微波干燥符合薄层干燥模型,可用Page模型描述本试验干燥过程,通过SPSS分析得出Page模型参数k、n值与微波功率Q、负载量m、真空度Pw之间的回归方程:k=-0.03+3.4× 10-4Q-3.205×10-4m+0.6Pw、n=1.467-1.61×10-3Q+3.63×10-3m-7.2Pw,得出Page模型表达式.     

枣片的预处理及干燥方式研究

以木枣为实验材料,探讨不同的脱水预处理和干燥方式对枣片品质的影响。采用真空渗糖的方式对枣片进行脱水预处理,改变糖的种类和配比,对经预处理和干燥后的枣片进行综合评定,选择出一种较佳的糖液配方和干燥方式。研究结果表明,糖液的最佳配比为25%蔗糖、35%葡萄糖,产品的综合得分高达96.87。采用真空低温方法干燥枣片,所得产品品质较佳、加工时间短。     

超声预处理对杏片微波冻干过程中水分迁移的影响

为探究超声前处理对杏片微波冷冻干燥(MDF)过程干燥特性以及水分迁移扩散特性,以鲜杏为原料,采用微波冷冻干燥技术,使用低场核磁共振技术,测定不同超声前处理条件下杏片MFD干燥过程中的横向弛豫时间T2反演谱。结果表明:超声前处理对杏片MFD前期干燥速率影响较大。扫描电镜观察发现,内部结构最佳的超声处理条件为350 W,35℃,15 min,有利于水分迁移。新鲜杏中所含自由水约占总水分的83%。通过对不同超声处理条件的杏片在干燥过程中内部各状态水分的迁移规律分析发现:随着干燥的进行,部分自由水先向结合水的方向迁移,同时弱结合水逐渐向结合水迁移,结合水向弱结合水的迁移则贯穿整个干燥过程。不同超声前处理条件下杏片干燥过程中有效水分扩散系数变化范围是8.44×10~(-11)~15.00×10~(-11) m~2/s,超声处理使杏片的有效水分扩散系数提高了82.29%~223.97%。     

胡萝卜片的微波干燥工艺条件优化

对胡萝卜片的微波干燥工艺条件进行了初步研究,通过单因素及正交试验探讨了不同微波处理对胡萝卜片的失水率、感官品质、复水性等的影响,得到了微波干燥胡萝卜片的最佳工艺条件。     

胡萝卜片的微波干燥工艺条件优化

对胡萝卜片的微波干燥工艺条件进行了初步研究，通过单因素及正交试验探讨了不同微波处理对胡萝卜片的失水率、感官品质、复水性等的影响，得到了微波干燥胡萝卜片的最佳工艺条件。     

果蔬微波真空干燥（MVD）技术研究进展

为了提高甘薯干燥效率和改善产品品质,本文采用微波真空干燥（MVD）技术,研究了超声处理（US）、渗透脱水（OD）、超声辅助渗透（USOD）、真空辅助渗透（VAOD）和超声/真空辅助渗透（VUOD）对甘薯切片干燥动力学、微观结构、孔隙特征及理化性质的影响。采用Weibull分布函数和Dincer模型对干燥曲线进行拟合,并结合尺度参数（α）、形状参数（β）、滞后因子（G）、干燥系数（S）、毕渥数（Bi）探讨了MVD甘薯切片干燥过程的热、质传递机制。结果表明：相比其他处理,USOD和VUOD可显著提高甘薯切片的水分流失率（WL）和固形物增加率（SG）（P<0.05）。Weibull分布函数和Dincer模型对MVD甘薯切片的干燥曲线具有较好的拟合效果。模型参数（α, β, G, S）结果表明,经USOD处理的MVD甘薯切片干燥效率最高,加速阶段历时最短;毕渥数（Bi）处于0.243~3.617之间,表明MVD干燥过程甘薯切片温度变化由内部传导热阻和表面对流热阻共同控制。基于Weibull和Dincer模型计算获得的水分扩散系数D_cal和D_eff分别为7.986×10⁻⁸~1.249×10⁻⁷和1.508×10⁻⁸~8.272×10⁻⁸ m²/s,且均是USOD样品最大,OD最小。USOD和VUOD甘薯切片呈现蜂窝状、多孔结构,其中VUOD样品孔隙率最大（为33.30%）,而USOD样品平均孔径最小（仅为164.50 nm）、迂曲度最大（为41.97）。相比其它预处理,USOD和VUOD处理显著提升了MVD甘薯切片的复水性能（P<0.05）,降低了体收缩率,较好地保持了原有色泽,缩小了色差。研究结果可为甘薯切片的微波真空干燥条件筛选和品质调控提供参考。     

Mass transfer characteristics during convective,microwave and combined microwave–convective drying of lemon slices

BACKGROUND: The investigation of drying kinetics and mass transfer phenomena is important for selecting optimum operating conditions, and obtaining a high quality dried product. Two analytical models, conventional solution of the diffusion equation and the Dincer and Dost model, were used to investigate mass transfer characteristics during combined microwave‐convective drying of lemon slices. Air temperatures of 50, 55 and 60 °C, and specific microwave powers of 0.97 and 2.04 W g^?1 were the process variables. RESULTS: Kinetics curves for drying indicated one constant rate period followed by one falling rate period in convective and microwave drying methods, and only one falling rate period with the exception of a very short accelerating period at the beginning of microwave‐convective treatments. Applying the conventional method, the effective moisture diffusivity varied from 2.4 × 10^?11 to 1.2 × 10^?9 m² s^?1. The Biot number, the moisture transfer coefficient, and the moisture diffusivity, respectively in the ranges of 0.2 to 3.0 (indicating simultaneous internal and external mass transfer control), 3.7 × 10^?8 to 4.3 × 10^?6 m s^?1, and 2.2 × 10^?10 to 4.2 × 10^?9 m² s^?1 were also determined using the Dincer and Dost model. CONCLUSIONS: The higher degree of prediction accuracy was achieved by using the Dincer and Dost model for all treatments. Therefore, this model could be applied as an effective tool for predicting mass transfer characteristics during the drying of lemon slices. © 2012 Society of Chemical Industry     

Drying features of microwave and far-infrared combination drying on white ginseng slices

Food Science and Biotechnology - In this study microwave and far-infrared combination drying were conducted to investigate the effect of microwave and far-infrared heating mode switching point...     

即食慈姑片微波干燥特性及动力学模型研究

以慈姑为原料,研究了慈姑片厚度、铺料密度、微波功率对微波干燥特性的影响,建立干燥动力学模型。结果表明,慈姑片微波干燥过程中主要表现为加速干燥和降速两个阶段,但当功率密度比较小时,干燥速度曲线出现恒速阶段。慈姑片越厚、铺料密度越大,干燥速率变化越小,干基含水率降低越缓慢,干燥耗时越长;微波功率密度越大,干燥速率变化越大,干基含水率下降越快,干燥时间越短;即食慈姑片微波干燥过程符合Page模型,模型预测值与试验值拟合良好(R²=0.990 66)。