Evaluation of Factors Influencing Microwave Osmotic Dehydration of Apples Under Continuous Flow Medium Spray (MWODS) Conditions

Microwave osmotic dehydration under continuous flow medium spray (MWODS) conditions is an innovative concept with high potential for enhancing moisture loss as well as improving product quality. Quantification of mass transfer kinetics under different processing conditions is important for managing and optimizing the osmotic dehydration process. A response surface methodology was used for evaluating and quantifying the moisture loss and solids gain kinetics of apples during the MWODS process. Experiments were designed according to a central composite rotatable design with all independent variables included at five levels (sucrose concentration, 33.3–66.8°Brix; medium temperature, 33.3–66.8 °C; medium flow rate, 2,120–3,480 ml/min; and medium contact time, 5–55 min). The process responses were moisture loss (ML), solids gain (SG), and weight reduction (WR) and were related to process variables using second-order polynomial regression models. The lack of fit was not significant (p?>?0.05) for any of the developed models. For ML, SG, and WR, the medium contact time was the most significant factor during the MWODS process followed by medium temperature and sucrose concentration. The effect of medium flow rate was only significant with moisture loss and weight reduction. The quantity of ML, SG, or WR achieved over a 30 min treatment time was chosen as the drying rate. These rates were shown to be responsive to the osmotic treatments increasing with sucrose concentration, medium flow rate, and medium temperature.     

樱桃番茄真空渗透预脱水工艺优化

以苏龙一号樱桃番茄作为试材,通过比较烫漂划线、针刺、划线、超声波预处理方法,确定了烫漂划线作为真空渗透预脱水的预处理方法。在该基础上,运用单因素试验研究了真空度、糖液浓度、渗透温度、渗透时间对樱桃番茄渗透预脱水效果的影响,进而确定真空度为0.080MPa,并应用响应曲面法优化其它参数,得出樱桃番茄真空渗透预脱水的最佳工艺条件为:糖度50°Brix、温度53.37℃、时间4.88h,该条件下樱桃番茄失水率与固形物增加率比值最大,为7.24。     

雪莲果超声波辅助渗透脱水工艺参数的优化

以渗透脱水温度、时间、蔗糖质量分数、超声波功率和处理时间为因素,以失水率(water loss,WL)和固形物增加率(sugar gain,SG)为指标,通过单因素试验,研究雪莲果的渗透脱水工艺参数。以渗透脱水温度、时间、蔗糖质量分数、超声波处理时间为因素,以WL、SG和二者比值(WL/SG)为指标,通过二次回归正交旋转组合试验设计建立雪莲果超声波辅助渗透脱水过程中各响应值(WL、SG和WL/SG)与各因素之间的回归方程,并得到超声波辅助渗透脱水的最优工艺参数。结果表明,超声波辅助处理可显著提高雪莲果渗透脱水效果;影响WL的因素主次顺序是温度＞时间＞蔗糖质量分数＞超声波处理时间;影响SG的因素主次顺序依次是渗透脱水时间＞超声波处理时间＞温度＞蔗糖质量分数;影响SG/WL的因素主次顺序是渗透脱水时间＞蔗糖质量分数＞超声波处理时间＞温度。雪莲果超声波辅助渗透脱水的最佳工艺参数为渗透脱水温度41℃、时间1.7h、蔗糖质量分数60.18%、超声波处理时间35min。在此组合参数条件下,SG/WL平均值为0.059。     

Optimization of Vapor Induced Puffing in Apple Dehydration

Vapor induced puffing during high temperature fluidized bed (HTFB) dehydration of apple cubes was optimized using response surface methodology (RSM). Osmoblanching in sugar syrup prevented enzymatic browning. Successtil puffing was achieved by creating a surface barrier to vapor by dipping the cubes in starch solution and manipulating the temperature and time of exposure in the HTFB. Optimum conditions for minimum bulk density with acceptable levels of nonenzymatic browning included dipping osmoblanched apple cubes in 1% starch solution, followed by HTFB drying 11 min at 157°C. Product bulk density exhibited a minimum while nonenzymatic browning values did not display an optimum. Minimum value of bulk density predicted by RSM and browning values were very close to those verified experimentally for product processed under the identified optimum conditions.     

热风联合真空微波膨化鸭胸肉工艺优化

以鸭胸肉为对象,优化真空微波膨化鸭胸肉的最佳工艺条件。采用单因素试验考察膨化前水分含量、微波强度、微波时间和真空度对膨化鸭胸肉体积收缩率、复水比、感官评分的影响,利用响应面试验优化热风联合真空微波膨化鸭胸肉的工艺条件。结果表明:膨化前水分含量、微波强度、微波时间和真空度对膨化鸭胸肉的品质均有一定影响。在固定真空度为0.08 MPa条件下,各因素对膨化鸭胸肉体积收缩率和感官评分的影响程度大小顺序均为微波强度微波时间膨化前水分含量,通过等高线叠加法确定最佳膨化鸭胸肉加工工艺参数范围:膨化前水分含量为59%~63%,微波强度为20.5~24.7 W/g,微波时间为6.1~6.6 min。在此条件下,膨化鸭胸肉的体积收缩率可低于34%,感官评分在4.75以上,研究结果可为鸭肉膨化食品工业化生产提供理论参考。     

基于渗透预处理的罗非鱼片微波干燥动力学

采用渗透-微波联合干燥技术对罗非鱼片进行干燥,研究渗透后罗非鱼片微波干燥过程的失水特性及其动力学,探讨渗透预处理、微波功率和装载量对罗非鱼片微波干燥过程的影响。结果表明:罗非鱼片微波干燥过程中,按失水速率大小,可分为升速干燥、恒速干燥和降速干燥3个阶段;经过渗透预处理的实验组其失水速率明显高于对照组;物料的失水速率随微波功率和装载量的增大而增大。此外,研究罗非鱼片微波干燥动力学,建立数学模型,发现Midilli模型拟合良好,较准确地预测了罗非鱼片微波干燥过程中的水分变化规律。     

响应面法优化渗透脱水板栗工艺

研究了渗透脱水板栗的最佳工艺,以浓度(45%～65%)、温度(20℃～60℃)、液固比(6.25∶1～25∶1)、时间(60 min～540 min)为自变量,失水率和固形物得率为响应值,通过可旋转中心组合试验设计,得到最大失水率和最小固形物得率的条件为:糖质量浓度52.58%、温度40℃、液固比13.72∶1、渗透时间474.17 min。在此条件下失水率23.94%、固形物得率5.41%。     

超声波强化紫薯渗透脱水工艺

分别以蔗糖质量分数、渗透温度、渗透时间和超声波功率为单因素,研究其对紫薯超声波渗透脱水的脱水率和固形物增加率的影响。以各因素为自变量,以脱水率和固形物增加率为因变量,对紫薯渗透脱水进行响应面工艺研究,得出最优工艺参数。结果表明：影响脱水率和固形物增加率的主次顺序均为渗透时间＞渗透温度＞糖液质量分数＞超声波功率;响应面优化最优工艺参数为糖液质量分数56.29%、渗透液温度65℃、渗透时间2.46h、超声波功率142.33W。结合实际操作,响应面优化的最优工艺调整为糖液质量分数56%、渗透液温度65℃、渗透时间2.5h、超声波功率140W,经验证,此条件下脱水率为40.79%,固形物增加率为8.33%。     

Physico-Chemical and Mechanical Properties of Apple Disks Subjected to Osmotic Dehydration and Different Drying Methods

The effect of sucrose infusion (SI) pretreatment and dehydration methods (freeze and air drying) on physical and textural properties of apple disks were analyzed. Dried samples were humidified between 11% and 43% relative humidity (RH) at 20 °C. Control samples (air- and freeze-dried) behaved similarly regarding water sorption and glass transition temperature. SI process caused important changes in the water sorption behavior of air-dried samples. Nuclear magnetic resonance relaxation times values (T ₂) for freeze-dried apples were higher than those for air-dried samples. Samples subjected to previous SI always presented lower T ₂ values because they had lower water contents. The dehydration method also affected the mechanic behavior. Air-dried samples exhibited higher F _max values during puncture assay than those obtained for freeze-dried samples. SI samples showed higher F _max values for both drying methods. The crust formed during air drying generated crispier materials along the whole RH range, while freeze-dried matrices were more deformable with the increase in RH. SI pretreatment also allowed diminishing browning development. The results obtained are useful in the choice of processing technologies of organoleptically acceptable dehydrated fruits for direct consumption or for their incorporation into compound foods.     

Mass Transfer Modeling and Shrinkage Consideration during Osmotic Dehydration of Fruits and Vegetables

During osmotic dehydration of fruits and vegetables, as water and/or other substances are removed from the material, shrinkage follows depending on the extent of net mass loss. Mass transfer is usually predicted through modeling. However, common models developed for osmotic dehydration of fruits and vegetables make assumptions that often deviate far from reality, including large heterogeneity, variability and complexity in properties of fruits and vegetables. This generates some skepticism about such models and minimizes their potential industrial reliability. This paper reviews osmotic dehydration of fruits and vegetables through a basic approach, provides a critical view on modeling and points out the factors that affect shrinkage and mass transfer based on an extensive evaluation of pertinent literature.     

Mathematical Modeling and Simulation of Microwave Thawing of Large Solid Foods Under Different Operating Conditions

Microwaves require shorter times to increase foodstuffs temperature when compared to conventional heating methods. However, there are some problems associated to temperature distribution within the products, owing to the preferential absorption of electromagnetic energy by liquid water, caused by differences between its dielectric properties and those of ice (“runaway”). To analyze the behavior of food microwave thawing, a mathematical three-dimensional (3D) model was developed by solving the unsteady-state heat and mass transfer differential equations; this model can be applied to large systems for which Lambert’s law is valid. Thermal, mass transport, and electromagnetic properties varying with temperature were used. The numerical solution was developed using an implicit Crank–Nicolson finite difference method using the classical formulation for one-dimensional (1D) systems and the alternating direction method in two and three dimensions. The model was validated using experimental data from the literature for 1D and two-dimensional conditions and with experiments performed in our laboratory for 3D heat transfer using frozen meat. It was applied to predict temperature and water concentration profiles under different thawing conditions in meat products and to simulate the effect of a fat layer located at the surface of the meat piece on temperature profiles. For different product sizes in rectangular geometry, numerical simulations demonstrated that microwave thawing times were significantly lower in comparison to conventional thawing methods. To prevent overheating during thawing, the combination of continuous microwave power with simultaneous application of air convection and the application of microwave power cycles, using refrigerated air convection with controlled surface temperature, were analyzed.     

Osmotic Dehydration of Tomato in Sucrose Solutions: Fick's Law Classical Modeling

ABSTRACT:  Osmotic dehydration of tomato was modeled by the classical Fick's law including shrinkage, convective resistance at the interface and the presence of water bulk flow. Tomato slices having 8 mm thickness were osmotically dehydrated in sucrose solutions at 50, 60, and 70 °Brix and at 35, 45, and 55 °C. Other experiments were done in a 70 °Brix sucrose solution at 35 °C with tomato slices of 4, 6, and 8 mm thickness and at different motion levels (velocities 0, 0.053, and 0.107 m/s). Tomato weight, water content, and °Brix of the products were measured as a function of processing time (20, 40, 80, 160, and 320 min). Results showed that temperature, concentration, thickness, and solution movement significantly influenced water loss and sucrose gain during the osmotic dehydration of tomato. The model predicted the modifications of soluble solid content and water content as a function of time in close agreement with the experimental data. Experimental Sherwood number correlations for sucrose and water were determined as Sh _s = 1.3 Re ^0.5 Sc _s^0.15 and Sh _w = 0.11 Re ^0.5 Sc _w^0.5, respectively. The effective diffusion coefficients of water (4.97 10⁻¹¹– 2.10 10⁻¹⁰ m²/s) and sucrose (3.18 10⁻¹¹– 1.69 10⁻¹⁰ m²/s) depended only on temperature through an Arrhenius-type relationship.     

Modeling of Coupled Water Transport and Large Deformation During Dehydration of Apple Tissue

Water loss of fruit during storage has a large impact on fruit quality and shelf life and is essential to fruit drying. Dehydration of fruit tissues is often accompanied by large deformations. One-dimensional water transport and large deformation of cylindrical samples of apple tissue during dehydration were modeled by coupled mass transfer and mechanics and validated by calibrated X-ray CT measurements. Uni-axial compression–relaxation tests were carried out to determine the nonlinear viscoelastic properties of apple tissue. The Mooney–Rivlin and Yeoh hyperelastic potentials with three parameters were effective to reproduce the nonlinear behavior during the loading region. Maxwell model was successful to quantify the viscoelastic behavior of the tissue during stress relaxation. The nonlinear models were superior to linear elastic and viscoelastic models to predict deformation and water loss. The sensitivity of different model parameters using the nonlinear viscoelastic model using Yeoh hyperelastic potentials was studied. The model predictions proved to be more sensitive to water transport parameters than to the mechanical parameters. The large effect of relative humidity and temperature on the deformation of apple tissue was confirmed by this study. The validated model can be employed to better understand postharvest storage and drying processes of apple fruit and thus improve product quality in the cold chain.     

微波生产咸干花生的失水特性及工艺优化

采用微波干燥技术代替传统加热烘烤,研究不同微波功率、载物量条件下花生果的失水特性,结果显示,花生果样品在微波干燥条件下的失水特性表现为两个阶段,即出现两个失水高峰,出现高峰的时间、最大失水速率随载物量、微波功率不同而不同。以微波功率、载物量、微波时间为3因素,咸干花生果终产品的失水速率、耗电量、感官评定为3指标,根据Box-Benhnken中心组合试验设计原理,利用Design expert7.0.1软件分析优化微波生产咸干花生的工艺条件并建立回归模型。结果表明:微波功率、载物量、微波时间对失水速率和单位耗电量均有极显著的影响,载物量对产品感官评定有显著的影响;优化的最佳工艺条件为:微波功率800W、载物量54.25g、微波处理时间3.5min,此时失水速率为5.79g/min,单位耗电量为0.76kW·h/kg,感官评定为9.17分。     

Osmotic Dehydration of Tropical Fruits and Vegetables

Because of the microstructural complexity of plant tissue, osmotic dehydration cannot simply be explained as a pure osmotic process in which cell membranes act as a semipermeable barrier allowing water to pass through. Instead, osmotic dehydration is considered a process in which many simultaneous mechanisms, acting at different levels, are responsible for mass transport. Different compositional and structural profiles are induced in fruits and vegetables, depending on process variables and the tissue microstructure. Compositional-structural profiles that are developed with gas-liquid exchanges in the tissue during osmotic process have a significant impact on physical (optical), textural and chemical properties (e.g., flavour profile) of the final product, which is in part influenced by the differences in the number of cells that are altered and unaltered during the treatment. This review focuses on changes in the physical, chemical, and cellular structure of fruits and vegetables, some technologies commonly applied to increase mass transfer during osmotic dehydration (OD), potentials and industrial applications of OD, and the challenges of osmo-drying technology.     

超声波辅助渗透脱水处理及其对西兰花冻结品质的影响

以西兰花为试材,在单因素试验的基础上,以水分流失和西兰花冻结-解冻后硬度为考察指标,通过正交试验优化西兰花冷冻前超声波辅助渗透脱水工艺条件。结果表明,渗透脱水最佳工艺条件为:超声波功率240 W,超声时间30 min,渗透液质量分数50%,在此工艺条件下,西兰花的水分流失为1.26,硬度为39.59 N。在此工艺条件的基础上,对比了普通渗透脱水(OD)和超声波辅助渗透脱水(UOD)对西兰花冻结效率和品质的影响。结果表明:UOD可以在短时间内达到OD较长时间的渗透效果,提高西兰花的冷冻效率,减少西兰花冻藏期的汁液流失,抑制抗坏血酸含量的减少以及色泽的变化。