魔芋片热风对流干燥速率影响因素

研究魔芋片在热风对流干燥过程中芋片干燥速率变化,以及温度和干燥介质流量对其的影响.研究结果表明:魔芋片的对流干燥过程可分为预热期、恒速干燥期和降速干燥期3个阶段;升高干燥温度和增大干燥介质流量,会使干燥速率增大,恒速干燥期缩短,降速期干燥速率下降加快,110℃是魔芋片对流干燥的最佳温度.     

Effect of Drying Methods on Functional Properties of Tarhana: A Wheat Flour-Yogurt Mixture

ABSTRACT: Changes in functional and sensory properties of tarhana prepared by different drying methods were investigated. While tunnel-dried (TD) tarhana had significantly ( P < 0.05) higher foaming capacity compared to freeze-dried (FD), home-microwave-oven-dried (HMD) and industrial-microwave-dried (IMD) samples, the FD tarhana showed the highest protein solubility. All tarhana samples exhibited pseudoplastic behavior described by power-law model. The drying methods used appeared to influence water and oil absorption capacities and emulsifying activity of tarhana. Microwave-dried tarhana exhibited higher overall sensory rating and color acceptability.     

Mathematical Modeling of the Convective Drying of Fruits and Vegetables

A proposed mathematical model, based on physical and transport properties and mass and energy balances, was developed for unsteady transport of momentum, heat and mass in granular beds of agricultural products (fruits and vegetables) under convective drying conditions. The model utilized water sorption isotherm equations and the change in solid density due to shrinkage. The unsteady-state differential equations for temperature and moisture profiles within the product were numerically solved using a central finite difference scheme. Experimental data on drying conditions and product drying rates agreed with the calculated results. A design and operation parameters optimization scheme, tested for grapes, resulted in minimized drying time and high quality dried product.     

土豆对流干燥过程中温度场的数值模拟

根据土豆切样在对流干燥过程中发生的物理变化,基于费克第二扩散定律和傅立叶定律,建立了对流干燥系统传质传热过程的数学模型以及几何物理模型,并利用有限元数值模拟方法对干燥过程中土豆切样内部的瞬态温度场及其影响因素进行了仿真预测。最后,设计并采用对流干燥实验对数值模拟得到的代表性结果进行了验证,结果表明实验值与模拟值在趋势上表现了较好的一致性。     

Drying Behavior of Honey-Starch Mixtures

Drying behavior of honey-starch mixtures at constant external conditions were studied. Mixtures with 0, 10, 20, 30, and 40% starch and the balance in honey were coated on aluminum plates at 0.25 mm thickness and dried in a laboratory oven at 60°, 70°, and 80°C. A mass transfer model with two falling rate periods was developed. In the first falling rate period, mass transfer coefficient was a linear function of moisture content. It was a constant in the second falling rate period. Mass transfer coefficients were also found to be affected by temperature and the starch content of each mixture.     

干燥方式对新疆方便汤饭面片干燥特性、品质及微观结构的影响

通过对面片进行蒸汽微波熟化,探究微波干燥(MD)、热风干燥(HD)、微波-热风联合干燥(MD-HAD)、微波-真空联合干燥(MVD)、真空-冷冻联合干燥(VD-FD)五种干燥方式对面片的干燥特性、剪切力、蒸煮特性、微观结构及感官评价的影响.结果表明:面片失水速率为:MVD>MD>MD-HAD>HD,MVD面片在最小功率...     

Novel Application of Neutron Radiography to Forced Convective Drying of Fruit Tissue

Neutron imaging is a promising technique to study drying processes in food engineering as it is a non-intrusive, non-destructive technique, which provides quasi-real-time quantitative information of the water loss during drying and of the internal water distribution, at a high spatial and dynamic resolution. Particularly, the high sensitivity to water is its main advantage for drying studies, despite the limited accessibility to reactor facilities, which produce neutrons. This technique was used to investigate forced convective drying of fruit tissue (pear and apple), placed in a small wind tunnel. Water loss, water distribution in the sample and sample shrinkage were evaluated as a function of time. The water loss, determined quantitatively from neutron radiographs, was underestimated slightly compared to gravimetrical measurements. The overall drying behaviour agreed well with control measurements performed in a climatic chamber and was very similar for both fruit tissues. The corresponding shrinkage behaviour of both tissues was also similar. The large shrinkage, which is characteristic for soft biological materials such as food products, however, hindered post-processing to some extent. From the internal water distribution, the water gradients within the sample, induced by drying, were visualised and were found to predominantly occur at the air–material interface, indicating that the water transport inside the tissue dominated the water loss, instead of the convective exchange with the air flow. Neutron imaging was shown to exhibit unique benefits for studying drying processes of food.     

Moisture Loss Kinetics of Apple During Convective Hot Air and Isothermal Drying

Effective moisture diffusivity of cylindrical apple samples (0.7 and 1.4 cm diameter) was determined under convective hot air drying (40, 50, 60, and 70° C and 1.5 and 3 m/s air velocity). The effective moisture diffusivities obtained were in the range of reported values and were found to be temperature dependent according to the Arrhenius relationship. However, the prediction of moisture loss obtained from Fick's diffusion model failed to follow experimental drying curves. Temperature profiles during convective hot air drying showed temperature gradients. This lack of isothermal conditions may lead to inaccurate predictions of moisture loss. Therefore, a combined microwave-convective hot air apparatus, capable of providing isothermal drying conditions, was used to quantify the drying kinetics. Differences in effective diffusivities determined from convective (9.6–18.5 3 10²¹⁰ m²/s) and isothermal (20.3–37.6 3 10²¹⁰ m²/s) drying experiments were shown. Using effective diffusivities obtained under isothermal conditions, the Fickian model still did not predict moisture loss during isothermal drying. Due to the developing porous structure of apple during drying, it was hypothesized that drying of a hygroscopic porous material is limited by evaporation of water to water vapor. Therefore, an irreversible first-order kinetic model was proposed to predict isothermal drying of apple. Using the rate constant calculated from the slope of the normalized drying curves (0.08–0.17 min²¹), the model predicted accurate moisture loss at each temperature throughout the entire moisture range of 0.06–8.5 g/g dry solid.     

Effect of Vacuum,Microwave, and Convective Drying on Selected Parsley Quality

This article has been retracted.     

Drying of Garlic Slices Using Convective Pre-drying and Vacuum-Microwave Finishing Drying: Kinetics, Energy Consumption, and Quality Studies

Garlic slices were dehydrated by convective drying (CD) and by a combined method consisting of convective pre-drying followed by vacuum-microwave finishing drying (CPD-VMFD). Drying of garlic using VMFD led to samples with high values of lightness and slightly lower values of the coordinates a* and b*. The treatment CPD-VMFD significantly decreased the drying time from 630 min for CD to 49 min and contributed to an important energy saving compared with CD (54.4–86.3 %). The total drying time was shorter when vacuum microwaves were introduced earlier and microwave power was higher. The highest temperature (114 °C) was found for samples pre-dried to a moisture content of 60 % and then dried at 360 W while showing the lowest energy consumption (98?±?1 kJ?g^?1). In general, the total antioxidant capacity increased after drying of garlic slices; however, the content of total phenolic compounds showed the opposite trend, and thus other compounds, such as allicin, should be involved in the antioxidant capacity of dried garlic. Garlic slices were CP dried until 30 % of moisture content followed by VMFD at 240 or 360 W showed the best results in terms of energy consumption and antioxidant capacity.     

藜麦粉对冷冻面团特性及其面包品质的影响

将藜麦和小麦粉按一定比例混合,用快速粘度分析法测定混合粉糊化特性,流变仪测定了冻藏过程中小麦-藜麦冷冻面团的流变学特性,核磁共振法测定面团中水分迁移,并测定其发酵体积变化,最后分析了冷冻面团组织状态与产品品质的关系。结果表明：藜麦粉对冷冻面团及面包的品质均有改善。藜麦粉降低了混合粉体系的糊化粘度和崩解值。冻藏后,冷冻面团的弹性模量和粘性模量增加,小麦粉冷冻面团损耗角正切值增加了4.73%,添加量为5%时冷冻面团损耗角正切值仅增加0.41%;小麦冷冻面团自由水上升了3.90%,藜麦添加后仅上升2.40%,可见藜麦粉能冷冻面团降低水分迁移程度;同时,添加藜麦粉能维持面团面筋网络结构的完整性,发酵体积由26.42 mL/h增大到29.17 mL/h。不同添加量的藜麦粉对面团及面包的品质改善程度不同,最适添加量为10%,烘烤后面包比容为3.08 mL/g,硬度为2803.48 g。本研究可为开发藜麦冷冻面团提供理论基础,在藜麦新产品开发方面具有重要的指导意义。     

酶制剂及方便面改良剂对面团流变学特性的影响

生物活性酶乳化剂,方便面改良剂B在康师傅方便面3#粉中起着很重要的辅助作用.它们可以改变小麦粉面团的粉质拉伸特性,主要指标包括稳定时间和抗延伸阻力.本文就此进行研究和试验.     

基于收缩特性分析的叶丝快速对流干燥动力学模型

为准确表征叶丝脱水过程中的干燥动力学特性,分析了烤烟和白肋烟两种叶丝在下行床快速对流干燥中的孔隙结构变化特征,对叶丝干燥收缩过程进行了数学模型拟合,建立了考虑收缩形变的叶丝干燥过程水分扩散模型,并对模型进行了验证。结果表明:①随着干燥过程中两种叶丝内孔容积的减小,叶丝中孔径大于0.5μm的孔容比例呈降低趋势,而孔径小于0.05μm的孔容比例呈升高趋势;在不同干燥阶段两种叶丝孔径分布的分形维数介于2.45~2.71之间,表明其孔隙结构具有分形特征;②线性叠加式收缩模型能够较好地描述叶丝干燥过程中的收缩现象,烤烟叶丝和白肋烟叶丝体积比V/V₀和含水率比X/X₀的线性相关系数均大于0.99,采用该收缩模型对基于Fick第二定律的水分扩散模型进行修正,实验数据的拟合精度从修正前的0.9069提升到修正后的0.9580;③采用修正的水分扩散模型描述叶丝快速干燥动力学发现,考虑了干燥过程中的叶丝收缩现象后,得到的叶丝水分有效扩散系数降低,表明叶丝干燥过程中的体积收缩不利于传质过程。      

A Traditional Turkish Fermented Cereal Food: Tarhana

Tarhana has a long history. According to historical records, it was first produced by Turkish people in Middle Asia and afterwards it spread out to different parts of the world. It is a fermented cereal-based food and can be simply defined as a mixture of yoghurt, cereal flours, yeast, different vegetables, herbs, and spices. After the mixing process, tarhana dough is fermented for 1 to 5 days and immediately dried. Both lactic acid bacteria (LAB) and yeast fermentations occur simultaneously during tarhana production. Therefore, tarhana has sour and acidic taste with yeast flavour as well. It is sun-dried at the home-made level or oven-dried of the commercial level. Several types of tarhana can be classified depending upon processing method or raw materials used. Low moisture (6-10%), low pH (3.5-5.0), and components (organic acids, bacteriosin, etc.) formed in fermentation have bacteriostatic effect on pathogens and spoilage microorganisms during long term storage (1-2 years) and enhance shelf life. Since tarhana is a good source of B vitamins, minerals, organic acids, and free amino acids, and since it is a product of LAB and yeast fermentation, it may be considered a functional and probiotic food.     

Wheat Dough Microstructure: The Relation Between Visual Structure and Mechanical Behavior

The microstructure of food matrixes, and specifically that of wheat-flour dough, determines mechanical behavior. Consequently, the analysis of such microstructure is both necessary and useful for understanding the physico-chemical and mechanical alterations during the production of cereal-based products such as breads. Confocal laser scanning microscopy (CLSM) is an established tool for the investigation of these matrix properties due to its methodical advantages such as easy preparation and handling, and the high depth resolution due to the optical sectioning of probes. This review focuses on the microstructure of wheat-flour dough from a mechanical and visual point of view. It provides an overview of the dependencies between the visibly detectable microstructural elements achieved by CLSM and the physical determined rheological properties. Current findings in this field, especially on numerical microstructure features, are described and discussed, and possibilities for enhancing the analytical methodology are presented.     

面团组成对鱼面面团及面片流变学特性的影响

采用粉质仪、拉伸仪、动态流变仪和质构仪研究了面团组成对鱼面面团和面片流变学特性的影响,以探索面团粉质指标、拉伸指标与面片弹性之间的关系。结果表明,添加鱼糜和变性淀粉使面团的流变学特性劣化,但加热后可以增强面片的弹性;盐既可增强面团的流变学特性,也可提高面片的弹性。在升温过程中,鱼糜对面团的黏弹性影响不明显,变性淀粉和盐可明显提高面团的黏弹性。面团的形成时间、稳定时间和最大拉伸阻力与面片的弹性相关性显著（p〈0．05）。