丁香鱼薄层干燥数学模型研究

为船上实际生产提供理论指导,对丁香鱼薄层干燥特性进行研究。通过单因素分析,对决定系数(R2),秩检验(χ2),均方根误差(RMSE)及平均相对百分误差(PE%)进行检验,确定了Midilli模型为丁香鱼热风干燥的最适模型。同时本实验采用二次正交旋转回归设计,以拟合Midilli模型各系数k、a、b、n与温度和风速之间的函数关系,建立丁香鱼热风干燥数学模型,并用该模型进行预测,其预测值与实验值拟合程度高。结果表明:Midilli模型可以对温度40～70℃,风速0.2～1.4m/s范围中丁香鱼水分变化进行较精确的预测。     

Conventional and intermittent drying modeling of agricultural products: A review

The purpose of this article is to present a discussion about recent technologies applied to processes involving intermittent drying of agricultural products, in addition to verifying the adjustment of mathematical models, both for conventional and intermittent drying, based on recent research in the literature. It was found that new mathematical models are being studied to describe the drying kinetics, one of which is the generalized Lewis model. Regarding intermittent drying, mathematical models are generally based on mass and energy balances. Furthermore, to obtain the mathematical modeling of intermittent drying for intermittent products, some researchers employ the effective diffusivity technique to describe all possible mechanisms of moisture movement, being estimated by Fick's second law of diffusion. Energy savings were also analyzed for different raw materials, ranging from 6% to 75%. It has been shown that the tempering time, and the conditions of the samples under study, affect energy consumption.     

百合热风薄层干燥特性及干燥品质

为提高规模化生产的百合品质,缩短干燥周期,以兰州百合为试样,运用JK-LB1700型薄层干燥试验台制干。系统研究了不同热风温度(60,70,80,90℃),热风速度(0.5,1.0,1.5,2.0m/s)和湿度(20%,30%,40%)对百合热风薄层干燥速率、色泽ΔE*值、VC含量、复水比的影响及各指标的变化规律;通过Weibull分布函数模拟了百合干燥过程及水分扩散规律。结果表明:随热风温度、热风速度增大百合热风薄层干燥时间显著缩短(P<0.01),不同相对湿度下无差异,但在干燥前期湿度大小与物料干燥速率呈正相关,后期呈负相关。采用Weibull分布函数能够准确(R2>0.99)描述百合热风薄层干燥过程,基于Weibull分布函数可准确获得百合薄层干燥水分有效扩散系数(1.213×10-6~3.992×10-6 m2/s),Deff值不仅受干燥参数影响,也受干燥设备和试样贮存时间的影响。试验干燥参数对百合品质指标色泽ΔE*值、VC含量和复水比的综合影响大小依次为干燥温度>热风速度>相对湿度,品质指标色泽ΔE*值和VC含量受干燥参数影响较大,复水比较小。     

胭脂萝卜薄层干燥的动力学模型及工艺优化

采用单因素实验研究热风温度、风速和切片厚度对胭脂萝卜干燥特性的影响,探讨了干燥过程中水分随时间的变化规律,建立胭脂萝卜热风薄层干燥的动力学模型;并在以上单因素实验的基础上,采用正交实验优化提取红色素的干燥工艺参数。结果表明:胭脂萝卜薄层干燥速率的影响因素由大到小是切片厚度>温度>风速;胭脂萝卜热风薄层干燥的动力学模型满足Page方程;提取红色素的最优参数为热风温度60℃、加热风速0.8 m/s、切片厚度6 mm,此时红色素提取量高达3.12%。      

农副产品干燥及其联合技术研究进展

随着时代的进步和人民生活水平的逐步提高,各种农副产品已基本实现工业化深加工,农副产品干燥技术是其深加工过程中必不可少的关键环节,其发展及应用受到越来越多的科研工作者的关注。本文首先介绍了几种国内外常用的干燥技术(热风干燥、真空冷冻干燥、微波干燥、喷雾干燥),然后重点论述了过热蒸汽干燥、中短波红外干燥、太阳能干燥、热泵干燥这4种新型干燥技术的优缺点及其联合应用技术,并对农副产品干燥技术未来的发展方向进行了展望。     

Emerging drying techniques for food safety and quality: A review

The new trends in drying technology seek a promising alternative to synthetic preservatives to improve the shelf-life and storage stability of food products. On the other hand, the drying process can result in deformation and degradation of phytoconstituents due to their thermal sensitivity. The main purpose of this review is to give a general overview of common drying techniques with special attention to food industrial applications, focusing on recent advances to maintain the features of the active phytoconstituents and nutrients, and improve their release and storage stability. Furthermore, a drying technique that extends the shelf-life of food products by reducing trapped water, will negatively affect the spoilage of microorganisms and enzymes that are responsible for undesired chemical composition changes, but can protect beneficial microorganisms like probiotics. This paper also explores recent efficient improvements in drying technologies that produce high-quality and low-cost final products compared to conventional methods. However, despite the recent advances in drying technologies, hybrid drying (a combination of different drying techniques) and spray drying (drying with the help of encapsulation methods) are still promising techniques in food industries. In conclusion, spray drying encapsulation can improve the morphology and texture of dry materials, preserve natural components for a long time, and increase storage times (shelf-life). Optimizing a drying technique and using a suitable drying agent should also be a promising solution to preserve probiotic bacteria and antimicrobial compounds.     

Hot air drying of whole fruit Chinese jujube (Zizyphus jujuba Miller): thin-layer mathematical modelling

Chinese jujube fruits were dried at 50, 60 and 70 °C in an electric heat blast dryer. Verma model was superior to the others for explaining change of moisture ratio in Chinese jujube by comparing thirteen commonly used mathematical models, suggested by the lowest percent error (1.211%). A strong linear dependence between drying rate and drying time was suggested by high values of determination coefficient ( R ² > 0.97). Linear model (effective diffusivity model) was found to be excellent adequacy in describing relationship between effective diffusivity, D _eff, and dry-basis moisture content, M . The effects of drying air temperature on the coefficients of the model were determined by multiple regression method. Lower percent error (3.44%) proved that the effective diffusivity model has higher precision. Our study indicated that it is possible to describe moisture content, drying rate, effective diffusivity, with the models including the effect of drying air temperature on the model constants and coefficients.     

Foam-mat drying technology: A review

This article reviews various aspects of foam-mat drying such as foam-mat drying processing technique, main additives used for foam-mat drying, foam-mat drying of liquid and solid foods, quality characteristics of foam-mat dried foods, and economic and technical benefits for employing foam-mat drying. Foam-mat drying process is an alternative method that allows the removal of water from liquid materials and pureed materials. In this drying process, a liquid material is converted into foam that is stable by being whipped after adding an edible foaming agent. The stable foam is then spread out in sheet or mat and dried by using hot air (40–90°C) at atmospheric pressure. Methyl cellulose (0.25–2%), egg white (3–20%), maltodextrin (0.5–05%), and gum Arabic (2–9%) are the commonly utilized additives for the foam-mat drying process at the given range, either combined together for their effectiveness or individual effect. The foam-mat drying process is suitable for heat sensitive, viscous, and sticky products that cannot be dried using other forms of drying methods such as spray drying because of the state of product. More interest has developed for foam-mat drying because of the simplicity, cost effectiveness, high speed drying, and improved product quality it provides.     

喷动床在农产品干燥中的研究进展

农产品干燥是农产品加工业中一项非常重要的技术,为农产品原料的利用和新产品的开发提供了更多可能.能效和干燥产品的质量是农产品干燥的2个关键指标,喷动床干燥技术是这2个关键指标的有效提高途径之一.该文简述了喷动床技术在干燥农产品的应用中的研究进展,介绍了喷动床的结构、工作原理及其应用现状,分析了喷动床干燥农产品主要的优缺点...     

间歇操作方式在厚层真空微波干燥中的应用

目的：为解决在厚层真空微波干燥过程中出现的物料沿床层厚度方向的水分分布不均匀，进而引起物料局部品质恶化（热斑或焦糊）等问题；方法：采用间歇干燥模式并对其水分分布的均匀性及干燥速率与连续干燥模式进行对比。结果：间歇干燥模式可改善物料的水分分布情况，并且间歇时间越长，水分分布的均匀性越好，但干燥速率会有所下降.     

食品生物技术在农产品副产物综合利用中的应用

生物技术是一门新兴的高新技术,对解决人类面临的食物、资源、健康、环境等重大问题发挥着越来越重要的作用。农产品生产和消费的日益增长,随之产生大量的农产品加工副产物。食品生物技术在副产物再利用中的应用也越来越广。本文综述了发酵工程、酶工程技术和生物分离工程等生物技术在农产品副产物综合利用中的应用。     

Prediction of moisture transfer parameters for microwave drying of lactose powder using Bi–G drying correlation

The mass transport properties characterising the drying of lactose powder were determined using a correlation proposed by Dincer and Hussain [Dincer, I. & Hussain, M. M. (2004). Development of a new Bi–Di correlation for solids drying. International Journal of Heat and Mass Transfer, 47, 653–658]. Experimental moisture content data for lactose samples dried under convective, microwave, combined convective-microwave and combined vacuum-microwave conditions were collected. The drying coefficients and lag factors were calculated from the experimental data and incorporated into the model. The Bi numbers were in the range 0.185–439, and moisture diffusivities and diffusion coefficients in the range from 0.135 × 10⁻⁹ to 102 × 10⁻⁹ and from 0.194 × 10⁻⁶ to 118 × 10⁻⁶ m/s, respectively. The predicted moisture profiles showed adequate agreement with the experimental observations, with the average error between experimental and predicted results being ±13.7%.     

方便米粉微波干燥特性的研究

本试验使用160、320、480、640和800 W的微波功率对方便米粉进行干燥,研究了方便米粉的微波薄层干燥特性,并采用8个常用的薄层干燥数学模型对试验数据进行拟合。结果表明:方便米粉的微波干燥过程可分为加速、恒速、降速3个阶段。Midilli-Kucuk模型具有较高的拟合度,能够较好的描述和预测样品干燥特性。通过Fick扩散模型计算出方便米粉微波干燥的有效扩散系数在1.44×10~(-9)~6.42×10~(-9)m~2/s之间。     

Thin layer drying characteristics of rapeseed (Brassica napus L.)

This study was performed to determine the most appropriate thin layer drying model and the effective moisture diffusivity of rapeseed. The thin layer drying tests were conducted at three different combinations of drying air temperature levels of 40, 50, and 60 °C and relative humidity levels of 30, 45, and 60%. The thin layer drying characteristics of rapeseed were determined. The Page (1949) model was the most adequate model for describing the thin layer drying of rapeseed. Drying occurred in the falling rate period and the rate of moisture removal from rapeseed was governed by the rate of water diffusion to the surface of the seed. Effective moisture diffusivities were calculated based on the diffusion equation for a spherical shape using Fick’s second law. Effective moisture diffusivity during drying varied from 1.72 × 10⁻¹¹ to 3.31 × 10⁻¹¹ m² s⁻¹ over the temperature range. The dependence of moisture diffusivity on temperature was described by an Arrhenius-type equation. The activation energy for moisture diffusion during drying was 28.47 kJ mol⁻¹.     

发展冻干食品企业的问题和建议

简述了国内外冻干食品行业发展概况和中国冻干食品企业的优势，指出中国冻干食品企业建立和运行过程中存在的一些问题，分析其原因，并提出解决这些问题的具体建议。最后介绍了清华大学核能技术设计研究院在食品真空冷冻干燥方面的研究工作。     

Convective hot air drying of blanched yam slices

In this study, a laboratory convective hot air dryer was used for the thin layer drying of blanched yam slices and experimental moisture ratio was compared with Newton, Logarithmic, Henderson and Pabis, modified Henderson and Pabis, approximation of diffusion, modified page 1, two-term exponential, Verma et al. and Wang and Singh models. Among all the models, the approximation of diffusion model was found to satisfactorily describe the kinetics of air-drying of blanched yam slices. The increase in air temperature significantly reduced the drying time with no constant rate period but drying occurs in falling rate period. The effective diffusivity values varied between 7.62 × 10⁻⁸ to 9.06 × 10⁻⁸ m² s⁻¹ and increased with increase in temperature. An Arrhenius relation with an activation energy value of 8.831 kJ mol⁻¹ showed the effect of temperature on moisture diffusivity.     

超临界CO2干燥技术在食品加工领域中的应用

超临界CO₂干燥技术在食品加工领域中的应用刚刚起步。简单介绍了常见的食品物料的干燥方法,超临界CO₂干燥的发展历史和分类,重点综述了超临界CO₂干燥食品物料的可行性、干燥过程和特点以及超临界CO₂干燥在食品加工领域的研究进展等,并对其发展前景做了展望。