Color Change Kinetics of American Ginseng (Panax quinquefolium) Slices During Air Impingement Drying

The color change kinetics of American ginseng (Panax quinquefolium) slices were investigated in an air impingement dryer under different drying temperatures (35, 45, 55, and 65°C) using the CIE Lab color parameters (L*, a*, b*) as the assessment indicators. Results illustrated that all three color parameters (L*, a*, b*) increased with drying time. The L* value decreased with increasing drying temperature. However, a* and b* values increased with the increase in drying temperature. Furthermore, at the initial drying stage the change rate of L* increased significantly, while towards the end of drying it reduced significantly. As regards a*, it slowly changed at the initial and final drying stages rather than in the intermediate drying stage. In the case of b*, it increased with increasing drying time and drying temperature during the whole process. The zero-order, first-order, and fractional conversion models were fitted to the experimental data, and the model's parameters were determined using linear regression analysis. By comparing the fitting of kinetic models to the experimental data, the most suitable model was selected to describe the color change kinetics. An Arrhenius equation was used to calculate the activation energy for color change kinetics and it was found that the values were 33.87–38.55, 56.48, and 74.03 kJ/mol for L*, a*, and b*, respectively. The findings of this work contribute to a better understanding of ginseng color changes kinetics during drying, and the established change kinetics models are a good tool for predicting, evaluating, and controlling of color change of American ginseng during its drying process.     

Dehydration modeling of Cordyceps militaris in mid-infrared-assisted convection drying system: Using low-field nuclear magnetic resonance with the aid of ELM and PLSR

Abstract

The changes in moisture content and shrinkage ratio of Cordyceps militaris during mid-infrared-assisted convection drying (MIRCD) with different drying temperatures (40, 50, and 60?°C) and velocities of airflow (1 and 2?ms^?1) were studied. The relationship between low-field nuclear magnetic resonance (LF-NMR) information and moisture content/shrinkage ratio was modeled using partial least-squares regression (PLSR) and extreme learning machine (ELM). Results indicated that the influence of drying temperature was more pronounced than that of air flow velocity. Both types of models showed good predictive ability with R²>0.90. The ELM models exhibited superior predictive performance than that of the PLSR models.     

Effects of ultrasound pretreatment on drying kinetics and quality parameters of button mushroom slices

The aim of this study was to investigate the utilization of ultrasound as a pretreatment method prior to drying to improve the quality of button mushroom slices during both hot air drying and far infrared drying processes. The effects of ultrasound and blanching pretreatments upon drying were analyzed. The ultrasound frequency was 40 kHz, the power was 0.4 W/cm², and the ultrasound energy was applied for 3 and 10 min, respectively. The ultrasound treatment caused reduction of the drying time by 9.5% in comparison to untreated samples. The drying kinetics of button mushroom slices were improved by ultrasound application, which involved an improvement of mass transfer coefficient and effective moisture diffusivity. The logarithmic model showed the best fit to the experimental drying data. For ultrasound treated samples, the parameters including hardness, crispness, rehydration ability, shrinkage, microstructure, and nutrient composition had remarkable changes compared with blanched and untreated samples.     

Finite element-based machine learning approach for optimization of process parameters to produce silicon carbide ceramic complex parts

Design and fabrication of silicon carbide ceramic complex parts introduce considerable difficulties during injection molding. Due to the great importance in processing optimization, an accurate prediction on the stress and displacement is required to obtain the desired final product. In this paper, a conceptual framework on combination of finite element method (FEM) and machine learning (ML) method was developed to optimize the injection molding process, which can be used to manufacture large-aperture silicon carbide mirror. The distribution characteristics of temperature field and stress field were extracted from FEM simulation to understand the injection molding process and construct database for ML modeling. To select the most appropriate model, the predictive performance of three ML models were estimated, including generalized regression neural network (GRNN), back propagation neural network (BPNN) and extreme learning machine (ELM). The results show that the developed ELM model exhibits exceptional predictive performance and can be utilized to predict the stress and displacement of the green body. This work allows us to obtain reasonable technique parameters with particular attention to the loading speed and provides some fundamental guidance for the fabrication of lightweight SiC ceramic optical mirror.     

干燥方式对红枣动力学及挥发性成分的影响

采用热风干燥、真空冷冻干燥和微波真空干燥对红枣进行干燥处理，结合顶空固相微萃取-气相色谱-质谱（headspace solid-phase microextraction-gas chromatography-mass spectrometry，HS-SPME-GC-MS）和电子鼻对枣片挥发性成分进行了分析，并对比了3种干燥方式对红枣色泽、动力学和挥发性成分的影响。结果表明，热风干燥和微波真空干燥对枣片色泽影响较大，真空冷冻干燥能够更好的保持原始色泽；对动力学方程进行拟合，发现Page 模型为预测红枣3种干燥方式干燥特性最适合的数学模型；干燥对枣片挥发性成分种类及相对含量差异显著，其中干燥前后相同的挥发性成分有19种。挥发性物质主要有酸类、酯类、醇类、醛类、酮类、烃类、杂环类和其他化合物，干燥过后枣片中酸类和烷烃类挥发性成分相对含量显著增加，醛类和杂环类物质显著降低。电子鼻结果表明干燥后枣片香气特征与新鲜红枣有较大的区别，热风干燥和微波真空干燥香味特征较为接近，微波真空干燥枣片的焦甜香特征更为明显。相较于热风干燥和真空冷冻干燥，微波真空干燥效率较高、能耗较低、周期较短，更适于制备干燥枣片。     

Continuous real-time monitoring and neural network modeling of apple slices color changes during hot air drying

A hot air drying system equipped with real-time computer vision system was used to investigate the effects of drying variables on apple slices color changes. Drying experiments were conducted at drying air temperatures of 50–70 °C, drying air velocities of 1–2 m/s, and samples thicknesses of 2–6 mm. A multilayer perceptron (MLP) artificial neural network (ANN) was also used to correlate color parameters and moisture content of apple slices with drying variables and drying time. The effects of drying air temperature and sample thickness on color changes were dominated over the effect of drying air velocity. However, non-linear and somewhat complex trends were obtained for all color parameters as function of moisture content. The MLP ANN satisfactorily approximated the color and moisture variations of apple slices with correlation coefficient higher than 0.92. Therefore, the computer vision system supplemented with ANN can be used as a non-invasive, low cost, and easy method for fast and in-line assessing and controlling of foodstuffs color and moisture changes during drying.     

Comparative Evaluation of the Effects of Electrohydrodynamic,Oven, and Ambient Air on Carrot Cylindrical Slices during Drying Process

Electrohydrodynamic (EHD) drying is a novel method of nonthermal drying. A corona discharge using multiple electrodes and a high-voltage electric field of 5.2 kV · cm^?1 was produced to investigate the drying enhancement of carrot slices and its effect on color and shrinkage. The EHD setup consisted of 13 stainless steel needle points connected to a DC power supply and a stainless steel plate. EHD⁺ drying, EHD^? drying, oven drying at 55°C, and ambient air drying control at 25°C for 5 h resulted in 79.5, 77.7, 77, and 22.5% total moisture removal from the fresh carrot slices, respectively. The final shrinkage of the EHD^± drying was less than that of oven drying but was higher than that of ambient air drying. It was estimated that the energy consumption of oven drying was several times greater than those of EHD^± drying. The conventional drying processes changed all color parameters, whereas the color for EHD^± dried samples remained almost the same. The carrot slices’ temperature during drying by EHD^± was significantly less than that of those dried by oven and ambient air drying.     

Ultrasound- and microwave-assisted intermittent drying of red beetroot

Abstract

A drying technique using a combination of high power airborne ultrasound, microwaves and hot air was applied to investigate the effect of intermittent drying on the process kinetics and several quality indicators of red beetroot. An innovative hybrid dryer was used in drying experiments. Six sets of drying programs were carried out. Ultrasound and microwaves were applied in convective drying continuously (hybrid processes) or periodically (hybrid intermittent processes). The drying processes were assessed in terms of drying time, drying rate, and energy consumption. Moreover, the total color change, retention of natural dye (betanin), water activity, texture, and microstructure of dry product were examined. The drying kinetics was well-fitted with the use of the Midilli-Kucuk model. It was found that hybrid intermittent drying reduces the total drying time and energy consumption, enhances both the drying rate and product quality. Furthermore, it was demonstrated that the hybrid intermittent drying can serve as an alternative to traditional hot air drying that could produce a more porous, nice color, and crispy vegetable product.     

Color Change Kinetics of Okra Undergoing Microwave Drying

In this present study, the effect of microwave output power and sample amount on color change kinetics of Turkey okra (Hibiscus esculenta L.) were investigated by using microwave drying technique. The color parameters for the color change of the materials were quantified by Hunter L (whiteness/darkness), a (redness/greenness), and b (yellowness/blueness) values. These values were also used for calculation of the total color change (ΔE), chroma, hue angle and browning index. The microwave drying process changed color parameters of L, a, and b, causing a color shift toward the darker region. The values of L and b decreased, whereas values of a and total color change (ΔE) increased during microwave drying. The mathematical modeling study of color change kinetics showed that L and b fit a first-order kinetic model, whereas a and total color change (ΔE) followed a zero-order kinetic model. However, chroma and browning index (BI) followed a first-order kinetic model, whereas hue angle followed a zero-order kinetic model. On the other hand, the data of the total color change (ΔE), chroma, hue angle, and browning index depending on the ratio of the microwave output power to sample amount were adequately fitted to a quadratic model. For calculation of the activation energy for color change kinetics parameters, the exponential expression based on Arrhenius equation was used.     

ASOS-ELM建模方法及在汽轮机热耗率预测中的应用

针对极限学习机（ELM）不能准确地预测汽轮机热耗率的问题,结合群智能优化算法,提出一种改进的共生生物搜索算法和极限学习机（ASOS-ELM）综合建模的方法。该方法利用改进的共生生物搜索（ASOS）算法优化ELM隐层激活函数的参数,求得最优的ELM模型。再将ASOS-ELM模型应用到热耗率建模中,首先用ELM初始化热耗率预测模型,以输出热耗率的均方根误差（RMSE）作为算法的适应度值,然后通过ASOS算法找到合适的ELM参数,从而得到准确的热耗率预测模型。并将热耗率预测的结果与传统的ELM模型、ASOS算法优化支持向量回归（SVR）模型、改进的粒子群算法（PSO）和基本的共生生物搜索算法（SOS）优化的ELM作对比。结果表明,ASOS-ELM模型在处理复杂的数据模型中,具有精确的预测能力与快速的收敛速度,为汽轮机热耗率建模提供了新思路。     

Study on quality attributes and drying kinetics of instant parboiled rice fortified with turmeric using hot air and microwave-assisted hot air drying

Abstract

This study investigated the quality and drying kinetics of instant parboiled rice fortified with turmeric (IPRFT) by using hot air (HA) and microwave-assisted hot air (MWHA) drying. The cooked long grain parboiled rice (LGPR) fortified with turmeric was dried with HA at temperatures of 65, 80, 95, and 110?°C. The microwave power density of 0.588 Wg^?1 was incorporated for drying with MWHA. Drying was performed until the dried IPRFT reached 16% (d.b.) of moisture content. The quality of the dried IPRFT was evaluated in terms of color, total phenolics content (TPC), total antioxidant capacity (TAC), rehydration ratio, volume expansion ratio, texture and microstructure. The results showed that the incorporation of microwave power with HA drying helped to reduce the drying time by 50% compared to conventional HA drying. A prediction of the moisture ratio by using the Page model provided the best R² and RMSE in drying kinetics. The drying conditions had small effects on the color, TPC, TAC, and microstructure of the dried IPFRT. The rehydration ratio, volume expansion ratio and texture of the rehydrated IPFRT showed minimal variations from changes in the drying conditions. The TPC and TAC of the dried IPRFT clearly increased compared to the TPC and TAC of the initial LGPR.     

Convective Drying of Ganoderma tsugae Murrill and Effect of Temperature on Basidiospores

In this study, drying of Ganoderma tsugae Murrill slices was carried out at different temperatures in a hot air circulating oven. The objectives were to investigate the drying characteristic and drying kinetics of the Ganoderma slices under constant air velocity and slice thickness. In addition, the effect of drying temperatures on the size and surface structure of Ganoderma tsugae basidiospores were studied. Using statistical analysis, a two-term model was found to fit best with the experimental data. Convective drying of Ganoderma tsugae slices at 60°C shows the minimum heat deformation to the size and surface structure of basidiospores.     

Modeling of combined far-infrared radiation and air drying of a ring shaped-pineapple with/without shrinkage

A ring shape is commonly used for industrial process of pineapple. Unfortunately, there has been no study on modeling of pineapple rings. Therefore we developed the mathematical model of pineapple rings during combined far-infrared radiation and air convection drying to investigate the evolutions of moisture content and qualities. The drying model based on the solution of Fick's law was used to estimate moisture diffusion coefficient (D). The D values with and without taking into account shrinkage phenomenon of dried products were compared. The kinetics of dried pineapple qualities such as color, shear force ratio and shrinkage during drying also were studied. Pineapples were pretreated, cut into rings and dried at far-infrared intensities of 1–5 kW/m² combined with air temperatures of 40–60 °C and air velocities of 0.5–1.5 m/s. The D values were found to increase with increasing intensity and air temperature. The D values with shrinkage consideration were lower than the D values without shrinkage consideration for all drying conditions. The quartic model gave a better fit over the other three polynomial models for describing the color kinetics. The thin layer drying models such as Page, Henderson and Pabis, Logarithmic and Midilli–Kucuk were modified in order to describe shear force ratio (SFR) of dried pineapple. The statistically analyses from this present study indicated that modification of drying models can be used to describe the kinetics of SFR and Midilli–Kucuk's form gave a better fit over the other form. The quadratic model was better than the linear model to predict shrinkage kinetics for all four dimensions (outer radius, inner radius, thickness and volume) of pineapple rings.     

Drying kinetics and evolution of the sample's core temperature and moisture distribution of yam slices (Dioscorea alata L.) during convective hot-air drying

In the present work, the drying kinetics and evolution of sample's core temperature and moisture distribution of yam slices during convective hot-air-drying were investigated. In terms of drying kinetics, the effect of drying temperature (50, 55, 60, 65, 70°C), relative humidity (20, 30, 40, 50%), and sample thickness (5, 7, 9 mm) on drying characteristics of yam slices were studied. Results indicated that all the three factors had significant influence on the drying kinetics, whereas drying temperature gave the most significant effect, followed by relative humidity and sample thickness. Moisture-effective diffusivity and activation energy were calculated, and it was found that the diffusivity was in the range of 5.5454 × 10^?10–1.0804 × 10^?9 m²/s and the activation energy was 29.528 kJ/mol. Heat and mass transfer models were developed based on the finite element method to calculate the core temperature and moisture distribution of yam slices during drying. Model validation exhibited good agreement between predicted and experimental data, which illustrated that the developed models could precisely predict the core temperature profile and moisture distribution of the sample. The current work provides further insights to understand the characteristics and mechanism of drying process of yam slices.     

Drying Kinetics of Tomato Slices in Vacuum Assisted Solar and Open Sun Drying Methods

A lab model vacuum-assisted solar dryer was developed to study the drying kinetics of tomato slices (4, 6, and 8 mm thicknesses) compared with open sun drying under the weather conditions of Montreal, Canada. The drying study showed that the time taken for drying of tomato slices of 4, 6, and 8 mm thicknesses from the initial moisture content of 94.0% to the final moisture content of around 11.5 ± 0.5% (w.b.) was 360, 480, and 600 min in vacuum-assisted solar dryer and 450, 600, and 750 min in open sun drying, respectively. During drying, it was observed that the temperature inside the vacuum chamber was increased to 48°C when the maximum ambient temperature was only 30°C. The quality of tomato slices dried under vacuum-assisted solar dryer was of superior quality in terms of color retention and rehydration ratio. The drying kinetics using thin-layer drying models and the influence of weather parameters such as ambient air temperature, relative humidity, solar insolation, and wind velocity on drying of tomato slices were evaluated.     

THE DEHYDRATION OF GARLIC. 1.DESORPTION ISOTHERMS AND MODELLING OF DRYING KINETICS

Abstract

Desorption isotherms for 1 mm thick garlic slices were determined at between 25 and 50°C and satisfactorily fitted with the G.A.B. equation. The kinetics of drying of slices of thickness 1.5 - 5.0 mm were determined at between 40 and 60°C using an air flow rate of 2.5 m-s^?, and the conditions affording a high-quality product m the shortest time were identified. After establishing how the effective diffusion coefficient of the garlic slices varied with their moisture content during drying, a diffusional model accounting for these variations was developed and satisfactorily fitted to the experimental kinetic data.     

Thin-Layer Drying Characteristics and Quality Evaluation of Air-Dried Ganoderma Tsugae Murrill

Ganoderma is normally dried to extend its shelf life without using chemical preservative and to concentrate the medicinal value in the fruiting body. Convective hot air drying characteristics of Ganoderma tsugae Murrill were evaluated in hot air circulated oven at different drying temperatures, sizes, and air flow rates. The drying kinetics of Ganoderma tsugae in kidney shape and slices were investigated and compared at different drying conditions. The variation of effective moisture diffusivity values at decreasing moisture contents during drying was determined from the drying data. Four well-known thin-layer drying models were fitted to the experimental data and the Midilli model was found to satisfactory describe the drying characteristics of kidney-shaped Ganoderma tsugae. Ganoderma tsugae dried at 50°C with air velocity of 1.401 ms^?1 showed the highest retention of crude ganoderic acid content compared to other drying conditions.     

Ascorbic Acid Thermal Degradation during Hot Air Drying of Camu-Camu (Myrciaria dubia [H.B.K.] McVaugh) Slices at Different Air Temperatures

Abstract

Air drying of camu-camu slices was performed in order to estimate the effect of air temperature on the kinetics of ascorbic acid thermal degradation. Moisture variation during the air drying process was monitored gravimetrically by weighing the trays at predetermined time intervals. The experimental points were adjusted by Fick's diffusion model and by the Page empirical model. The effective diffusion coefficient (D_eff) ranged from 8.48 × 10^?10 to 1.34 × 10^?9 m²/s.The ascorbic acid content was evaluated in samples taken during the drying process using Iodine titration, and the results modeled by the Weibull equation. Concerning ascorbic acid retention the best drying condition required air at 50°C. The ascorbic acid retention was 78%, when the moisture content of the product reached 10% (wet basis).     

基于FEEMD-AE与反馈极限学习机组合模型预测研究与应用

针对现有工业过程非平稳时间序列中的特征提取及预测问题,提出了基于快速集合经验模态分解（fast ensemble empirical mode decomposition,FEEMD）、近似熵（approximate entropy,AE）和反馈极限学习机（feedback extreme learning machine,FELM）的组合模型。首先,针对复杂非平稳时序数据,采用FEEMD方法将其分解为从高频到低频的相对平稳的本征模态函数分量和余项;其次,为解决经过FEEMD分解出来的分量复杂度问题,运用近似熵（AE）计算分量复杂度并进行特征重构,以降低分量复杂性;然后,基于传统ELM结构,通过引入反馈机制,在输出层与隐含层之间增加反馈层用来记忆隐含层输出数据,并计算数据趋势变化率动态更新反馈层输出,形成反馈极限学习机（FELM）,对非线性动态系统的下一时刻输出进行预测;最后,将所提出的组合预测模型通过UCI标准数据集与精对苯二甲酸（PTA）溶剂系统进行建模仿真,仿真结果表明,提出的组合模型预测方法能够得到较高的预测精度,为实际生产操作优化提供了一定的指导。     

Effect of Dipping Temperature and Dipping Time on Drying Rate and Color Change of Grapes

Thompson seedless grapes (Vitis vinifera) were pretreated in potassium carbonate and ethyl oleate solutions for 1, 2, and 3 min at 30, 40, 50, and 60°C and dried in a convective air dryer at 60°C. The effect of dipping time and solution temperature on drying rate and color kinetics were investigated. Grapes dipped into the solution at 60°C for 2 and 3 min had the fastest drying rate. Among the seven semi theoretical models compared, the Midilli equation best described the drying curves of grapes for all dipping pretreatments. Color data were obtained using a machine vision system in CIE L*a*b* color space. Regardless of the dipping time and temperature applied, all raisins had varying degrees of brown coloring. At all dipping times and temperatures the highest R ² value was obtained for a* values, which followed zero-order reaction kinetics during drying.