Reducing cracking and breakage of soybean grains under combined near-infrared radiation and fluidized-bed drying

Near-infrared radiation was combined with fluidized-bed drying to reduce the cracking and breakage of soybean grains because of its advantages such as a decrease in the moisture gradient and the stresses development within the grain kernel, leading to high quality of product. Physical qualities, i.e. cracking, breakage and colour, were investigated together with microstructure of soybean grains. Protein solubility and urease activity were also determined. The parameters studied were near-infrared radiation powers of 4, 6 and 8 kW, air velocity of 4.5 m/s, air temperature of 40 °C and grain bed depth of 6 cm. Results showed that the drying rate was increased with the increase of near-infrared radiation power. The moisture content was reduced from an initial moisture content of 20% d.b. to the final moisture contents of 13.5% d.b. (4 kW), 12.8% d.b. (6 kW) and 12.5% d.b. (8 kW). The cracking and breakage of soybean grains occurred negligible, which was lower than 4.4% and 5.3% for cracking and breakage, respectively. At near-infrared radiation powers of 4 and 6 kW was accepted for both soybean grains trade and animal feed industries in Thailand. The total colour difference changes (ΔE) were varied in the range of to 2.9-4.2. The protein solubility of final product was in an acceptable range (77-82%) for feed meal. The reduction of residual urease was varied in the range of to 39-70%. This study has demonstrated that the soybean grains under combined near-infrared radiation and fluidized-bed drying was properly treated.     

COFFEE DRYING IN A ROTARY CONDUCTION-TYPE HEATING UNIT

Parchment coffee (Arabica) was dried from an initial moisture content of about 90% to 10% dry basis (db) in a recirculating rotary conduction type heating unit at controlled plenum temperatures of 100, 120 and 140C or controlled product temperatures of 50, 60, and 70C. the temperature of the plenum or moving beans could be maintained at specified levels with small variations during coffee drying experiments. the color and specific gravity of coffee beans exhibited minimum changes as a result of drying operations. the susceptibility of coffee beans to breakage decreased with the lowering of moisture and attained minimum values in the moisture content range of 20 to 30% db. the breakage susceptibility increased sharply with further reduction in moisture content. A drying model, which considered product temperature‐time history alone under different operating conditions, estimated the change in moisture content adequately. Such a model could be used for computer‐based control of the coffee drying process.     

EFFECT OF HEAT TREATMENT ON THE INDUSTRIAL QUALITY OF TWO VARIETIES OF MEXICAN WHEAT

Two Mexican wheat varieties conditioned to three initial moisture levels (17, 25 and 37% dry basis) were dried with air at 40, 60, 80 and 100°C for 60 min periods in a laboratory scale fluidised bed system. Drying kinetics and activation energy was determined. Weight per hectolitre, wheat hardness, total protein content, dough mixing time and loaf volume were analysed. The results showed that the initial moisture content and drying velocity lowered the activation energy necessary to extract water from the grain. The effect of temperature and moisture content in the grain were the most important factors to control damage during drying. The hard wheat variety was less susceptible to heat damage than the soft variety, probably due to its higher protein content and harder texture. Weight per hectolitre, wheat hardness and drying did not considerably modify total protein content. Conversely, mixing time and loaf volume showed changes directly related to heat treatment severity. Fluidised bed drying at 40 and 60°C of both varieties at 17% initial moisture content showed an improving effect on loaf volume.     

Developing Hot Air-Assisted Radio Frequency Drying for In-shell Macadamia Nuts

Dehydration reduces water activity and extends shelf life of perishable agricultural products. The purpose of this research was to study the application of radio frequency (RF) energy in dehydration of in-shell Macadamia nuts and shorten the lengthy process times needed in conventional hot air drying operations. A pilot scale 27.12-MHz and 6-kW RF system was used to determine the operational parameters, the drying curve, and the quality attributes of the processed nuts. The results showed that an electrode gap of 15.5 cm and a hot air temperature of 50 °C provided an acceptable heating rate and stable sample temperatures, and were used for further drying tests. The drying curves showed an exponential decay and required 750 and 360 min to achieve the final moisture content of 0.030 kg water/kg dry solid (3.0 % dry basis) in whole nuts in hot air drying and RF heating/hot air combined drying, respectively. The drying kinetics of the nuts were described well by the Page model for hot air drying, but a logarithmic model was more suited for RF/hot air drying. Peroxide value and free fatty acid increased with the drying time both for hot air and RF drying but remained within acceptable range required by the nut industry. The RF process shows potential to provide rapid, uniform, and quality-acceptable drying technology for the nut industry.     

Effect on cell membrane structural integrity of xylitol‐coated probiotics when stabilised with milk solids – A FTIR study

Vacuum drying of sorbitol or xylitol‐coated Lactobacillus reuteri LR6 cells and fluidised bed drying with different excipients were compared for the cell viability post‐drying. L. reuteri cells coated with xylitol and desiccated in unsupported form or together with skim milk powder as an excipient were found to be better protected at high drying temperatures. Examination of the protein and polypeptide components of the cell envelopes via Fourier transform infrared spectroscopy revealed different degrees of structural deformation in individual samples, indicating milk solids as supporting excipient and fluidised bed drying helps in retaining high cell viability.     

Industrial paddy drying and energy saving options

Paddy drying is an energy-intensive process and influences rice quality. In this study, the energy consumption of paddy drying in a large-scale milling plant was investigated. Furthermore, some drying experiments were conducted in a laboratory. The aims were to gain practical information and to propose more economical drying options to the industry. The results indicated that the current drying in the plant consumed specific primary energy of between 3.874 and 4.421 MJ/kg of water evaporated. The experimental results showed that two-stage drying with tempering by using a fluidised bed dryer at 100–110 °C in the first stage and drying with ambient air using a solar dryer for the second stage provided rice quality that was comparable to that of the plant. Also, from the calculation, the energy cost of the plant could be reduced if an in-store dryer was used after the first-stage drying by LSU dryer.     

花生荚果固定床网袋堆垛通风干燥实验研究

为了解花生荚果固定床网袋堆垛通风的干燥特性、设备能耗情况以及荚果干后品质,使用固定床网袋堆垛通风(常温风)、固定床网袋自然堆垛、自然晾晒3种干燥方式对新鲜湿花生荚果进行干燥,探究了堆垛内不同位置花生荚果的干燥情况、温湿度变化、能耗情况,并对比分析了不同干燥方式下花生荚果的干后品质。结果表明,使用固定床网袋堆垛通风(常温风)干燥设备干燥花生荚果,花生荚果水质量分数由37.85%降至10.00%以下需要160 h;固定床网袋堆垛通风(常温风)干燥方法干后花生荚果的粗脂肪含量最高,为48.08%,色泽最优,同时除去花生荚果中单位质量水分需要消耗能量4.28×10⁶ J,远小于传统烘干;固定床网袋堆垛通风(常温风)较固定床网袋自然堆垛和自然晾晒有明显优势,干燥速率更快,干后品质更稳定。     

Effect of drying on the quality of milled rice

The effect of drying on the quality of milled rice was investigated. Variables studied were drying temperature, air velocity and air relative humidity. The degree of breakage during milling increased as temperature of drying increased (from 40 to 70°C) and relative humidity decreased. Varying the air velocity between 0.26 and 2.12 m/sec had no effect on breakage. The'activation energy' of grain breakage was much higher than of drying.     

QUALITY of ARTIFICIALLY DRIED LENTIL

The effects of artificial drying on Laird lentil qualities such as breakage susceptibility, cooking quality, and seed germination were determined at three initial moisture levels, 16%, 18%, 20% wet basis and seven levels of drying temperature varying from 40°C to 80°C. Cooking quality was not affected by drying in the range of treatments used in this study. High initial Omoisture content and lengthy drying periods at temperatures above 40°C were associated with increased seed breakage. Seed germination was particularly sensitive to heat treatment at 80°C and extended drying time for high moisture samples.     

Drying of chitosan in a spouted bed: The influences of temperature and equipment geometry in powder quality

The influence of temperature and spouted bed geometry in drying chitosan with relation to powder quality (molecular weight, deacetylation degree, particle size, color) and operation characteristics (product recovery and mass accumulated) were investigated. Chitosan paste was obtained from shrimp wastes and dried in a spouted bed (slot-rectangular and conical-cylindrical geometries) with different inlet air temperatures (90, 100 and 110 °C). Thermogravimetric curves, infra-red analysis and scanning electron microscopy were carried out in order to verify powder quality. Chitosan paste used in drying experiments showed solid content 4%, molecular weight 140 kDa and deacetylation degree 85%. In all drying experiments deacetylation degree was not modified and final moisture content was in the commercial range (10%). Temperature increase caused an increase in molecular weight, powder darkening and increased particle size. The best powder quality was obtained in slot-rectangular spouted bed at 90 °C. In this condition product recovery was 65%, accumulated mass was 20% and the powder presented faint yellow coloration, high thermal stability and porous heterogeneous surface.     

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。     

Characterization of hot-air drying and infrared drying of spearmint (<Emphasis Type="Italic">Mentha spicata</Emphasis> L.) leaves

In this study, spearmint leaves were dried using hot-air (HA) and infrared (IR) techniques. Dried products were comprehensively analyzed for their drying time, specific energy consumption (SEC), rehydration, essential oil content and color changes. The IR drying process was carried out at radiation intensity levels of 1562, 3125 and 4688 W/m², emitter to sample distances of 10, 15 and 20 cm and air temperatures of 30, 40 and 50 °C. For HA drying, three levels of air temperature (30, 40 and 50 °C) and air velocity (0.5, 1 and 1.5 m/s) were applied. The results indicated that drying time, SEC and color changes were lower in IR drying of spearmint than in HA drying. IR drying gave the highest essential oil content (0.95 %) and rehydration ratio (0.788 kg water/kg dry matter (DM)). Totally, it was observed that IR drying of spearmint resulted in better quality preservation and had lower energy costs in comparison to HA drying.     

Application of simulation in determining suitable operating parameters for industrial scale fluidized bed dryer during drying of high impurity moist paddy

A systematic approach has been developed for selecting the suitable drying parameters to be used for drying of high moisture and high impurity paddy with an industrial fluidized bed paddy dryer (10–20 t h⁻¹ capacity) based on targeted specific air flow rate and residence time during two typical paddy drying seasons. A mathematical model was developed by modifying an existing model and was simulated and validated with observed industrial drying data as well as data reported in the literature. Comparison between the observed and simulated results showed that the mathematical model is capable of predicting outlet paddy moisture content and air temperature well. Suitable operating parameters were determined for reducing any initial paddy moisture content (mc) down to 24–25% dry basis (db), the safe mc level after fluidized bed drying to maintain rice quality, to achieve maximum possible throughput capacity of the dryer with corresponding energy consumption. Based on these criteria, bed thickness at 10 cm, specific air flow rate of 0.05 kg kg⁻¹ s⁻¹ (for corresponding bed air velocity of 2.3 m s⁻¹), air temperature of 150 °C and residence time of 1.0 min were found to be suitable drying conditions for reducing paddy mc from 30 to 24.30% (db) in one season while the maximum throughput capacity of 15.7 tonne per hour (t h⁻¹) might be achieved. The specific electrical and thermal energy were 0.48 and 6.15 MJ kg⁻¹ water evaporated, respectively. On the other hand, the dryer capacity was found to be limited to 7.4 t h⁻¹ during drying paddy of higher initial mc (35% db). This approach might provide easy and comprehensive guidelines for selecting suitable sets of operating parameters for any industrial fluidized bed dryer at its possible maximum throughput capacity for drying of freshly harvested high moist paddy with a high level of impurities.     

葛根片热风干燥节能工艺条件优化研究

为了找寻葛根片热风干燥的最佳条件,利用热风干燥箱,在不同的沸水预处理时间、切片厚度、热风温度和装料量条件下对葛根片进行干燥,获得了葛根片的干燥曲线,并分析了沸水预处理时间、切片厚度、热风温度和装料厚度对干燥效果的影响。并以含水率和单位物料能耗为指标,利用响应面分析法（RSM）对热风干燥工艺条件进行优化,得到了葛根片热风干燥工艺参数的最佳组合为沸水预处理时间32 s、切片厚度4 mm、热风温度56 ℃和装料量1.4 kg/m2,在此条件下,经过44 h的干燥,葛根片干基含水率为5.9%、单位物料能耗为1.88 （kW·h）/kg。     

SIMULATION of CANOLA and BARLEY DRYING IN A DEEP BED

A mathematical model for a radial, continuous-crossflow dryer was modified and used to simulate the drying process in a fixed bed dryer. the predictions of the adapted model were compared with experimental test results for canola drying at the following drying conditions: airflow rates of 0.4 and 0.6 kg/(m²s), inlet air humidity 0.098 and 0.0114 kg/kg of dry air, initial grain moisture content 0.221 and 0.251 kg/kg dry basis. In both tests the inlet drying air temperature was kept at an average of 67.5°C. At the end of canola drying, the mean drying air temperature predicted by our model was within 1°C of the measured temperature and the mean predicted moisture content was within 0.5% of the measured moisture content, dry basis. Also, our model was verified against experimental results for barley published by other authors and against predictions from a published model for barley. the predictions from our model were in good agreement with the published experimental and predicted data. Simulations results for canola and barley drying in the same thickness of a deep bed were compared. Simulations were conducted to investigate the effects of canola properties such as bulk density and dryinig conditions of air such as airflow rate and air humidity on drying in deep beds of canola.     

Drying kinetics and quality of okara dried in a jet spouted bed of sorbent particles

Okara or soy residue is a byproduct of soymilk and tofu production process. Okara has high protein content and can be used as an ingredient in many food products or can be used as animal feed. However, okara deteriorates rapidly; hence raw okara must be dried as early as possible under appropriate conditions. Drying could also help eliminating undesirable antinutritional factors in okara. The present study investigated the feasibility of drying okara using a combined convection-sorption drying, i.e., the use of a jet spouted bed of sorbent particles. The effects of various parameters such as drying air temperature and velocity, mass ratio of sorbent particles to okara, and initial bed height of okara on the drying kinetics were investigated. Also, various quality attributes of okara viz. color, oxidation level, rehydration ability, urease activity and protein solubility as well as the specific energy consumption during drying were investigated in both low- and high-temperature ranges.     

营养冲调粥流化床干燥特性及动力学模型的建立

利用流化床干燥装置,对营养冲调粥（玉米、红豆、荞麦、燕麦和小米质量比为3.5∶3.0∶2.0∶0.7∶0.8,加水后经双螺杆挤压膨化制得）的流化床干燥特性进行实验研究,探讨干燥过程中不同风速、进风温度以及产品加工过程中的加水量对营养冲调粥干基水分质量分数和干燥速率的影响,得到了营养冲调粥流化床干燥的失水特性规律。根据实验数据建立营养冲调粥流化床干燥的动力学模型,并对模型进行统计检验。结果表明,经拟合得到营养冲调粥流化床干燥的最佳模型为Page模型,拟合方程为：ln（－ln MR）＝－4.064 63＋0.014 14T＋0.069 85v＋0.327 5H＋（0.570 96＋0.000 976 25T－0.009 68v－0.265 5H）ln t（T为进风温度/℃;v为干燥风速/（m/s）;H为原料加水量/%）,此方程能够较好地描述营养冲调粥的干燥过程,准确预测各阶段营养冲调粥的干基水分质量分数和干燥速率。     

Modeling engineering characteristics of hazelnut kernel during infrared fluidized bed drying

In this study, a laboratory scale infrared fluidized bed dryer was used to dry the hazelnut kernels. The drying experiments were performed under the following drying conditions: air temperatures of 45, 65 and 85?°C, air velocities of 1.30, 3.09 and 4.87 m/s and infrared powers of 500, 1000 and 1500 W. Maximum and minimum values of effective moisture diffusivity for hazelnut kernels were obtained 1.87?×?10^?9 and 1.75?×?10^?10 m²/s, respectively. Activation energy was obtained between 33.02 and 50.22 kJ/mol. Specific energy consumption of hazelnut kernels was obtained between 1.72?×?10³ and 2.23?×?10⁴ MJ/kg. Six mathematical models were used to predict the drying behavior of hazelnut samples. Among these models, the Midilli model sufficiently fitted the experimental drying data. The shrinkage values were obtained within the range of 0.10 and 0.24. The results obtained showed that the \({{L}^{*}},\) \({{a}^{*}},\) \({{b}^{*}}\) and \(\Delta E\) color values of the kernels were significantly affected (P?<?0.05) by air temperature. The highest color changes were related to the air temperature of 85?°C at all air velocities and infrared powers. Maximum values of energy (103.57 N mm) and force (129.84 N) at initial rupture point was related to air temperatures of 85?°C and infrared powers of 1500 W. Minimum values of energy (16.47 N mm) and force (31.74 N) at initial rupture point was related to air temperatures of 45?°C and infrared powers of 500 W.     

Quality aspects of heated-air drying of soybeans

Samples of 300 g of soybean seed, variety Forrest, conditioned to 14, 16 and 18% moisture content (m.c.; w.b.), were dried for 4 hr in a small batch fluidized-bed rig with a test section of 120 mm diameter and air flow rate set at 0.03 kg/s. Air inlet temperatures of 40, 50, 55, 60, 65, 70 and 80°C were used to determine the effects on quality. Conditioned and unconditioned samples, together with samples dried in the bed for 4 hr at room temperature, served separately as controls. Samples of 25 g of the conditioned seed, sealed in test tubes, were heated for 4 hr in an air oven at 40, 45, 50, 55 and 60°C to study the effect of heating at a constant m.c.Seed germination and seedling vigour clearly indicated the onset of heat damage and showed that no single criterion was more sensitive than any other. Safe drying air temperatures of 65, 60 and 55°C were obtained for initial moisture contents of 14, 16 and 18% respectively. Heating soybeans up to 60°C at a fixed m.c. increased the susceptibility to heat damage. Oil vield, free fatty acid content and fatty acid composition were not affected by any of the heat treatments. The peroxide value, however, showed some increase at temperatures above 50°C. Fluidizing at room temperature did not affect germination.The colour of crude oil, after heat bleaching, for 50–80°C heat treatments was paler than the controls, while 40°C gave a very dark colour. Degumming of oils followed by refining removed all detectable phospholipids from all samples and produced oils paler in colour, when heat bleached, except for 80°C at 16 and 18% m.c. which produced oils slightly but noticeably darker.Soybeans were found to dry slowly compared to sunflower seed and rapeseed, and the logarithmic drying model was fitted to the various drying curves. Computer program DRIER was modified to be applicable to soybeans and some runs were carried out for a farm batch radial-flow drier. Results indicated the advantage of using a high inlet air temperature provided that seed quality is not affected.     

Effect of different postharvest drying temperatures on Aspergillus flavus survival and aflatoxin content in five maize hybrids

After harvest, maize is dried artificially to halt fungal growth and mycotoxin production while in postharvest storage. The process often limits harvest capacity and has been a frequent cause of seed injury. Higher drying temperatures could lead to shorter drying periods and faster turnover; however, there is often a deterioration of the physical grain quality, including increased breakage susceptibility and loss of viability. The goals of this study were to determine the effect of different postharvest drying temperatures on Aspergillus filavus and Fusarium verticillioides survival and aflatoxin content in maize and to determine the viability of the seed. Five corn hybrids varying in resistance to A. flavus were side needle-inoculated with A. flavus, harvested at physiological maturity, and dried at temperatures ranging from 40 to 70 degrees C. Kernels were evaluated for aflatoxin, stress cracks, germination, and kernel infection by A. flavus and a natural infestation of F. verticillioides. Drying temperature had no effects on aflatoxin concentration given the heat stability of the toxin. With increased temperatures from 40 to 70 degrees C, germination decreased significantly, from 96 to 27%, and stress cracks increased significantly (1.4 up to 18.7). At temperatures above 60 degrees C, F. verticillioides kernel infection was significantly reduced to less than 18%. At 70 degrees C, there was a significant reduction in A. flavus kernel infection, from 11 to 3%. This information is useful in determining a range of temperatures that can be used for drying seed when fungal infection, stress cracks, and seed viability are of interest.