THIN LAYER METHOD ANALYSIS OF SPOUTED BED DRIED MALAYSIAN PADDY – CHARACTERISTIC DRYING CURVES

A lab‐scale spouted bed dryer was used for the drying of paddy. The Malaysian grown paddy is a sample of Geldart's Group D particle. Drying was carried out in the dryer at two different internal configurations, namely with or without the installation of a draft tube, and at several drying temperatures (60–90C), air flow rates (1.14–1.45 m/s) and bed heights (30–45 cm). Drying kinetics of paddy in spouted bed showed only induction and falling rate periods, without constant drying rate period. Thin layer method analysis shows characteristic drying rate curves of linear and exponential functions for the first and second falling rate period, respectively, in conventional spouted bed drying. A single power function was observed in spouted bed drying with a draft tube, mainly as a result of a better tempering effect that gave a lower drying rate gradient.     

Experimental and parametric study on drying of green peas in spouted bed

Drying of Green Peas (Pisum sativum) was studied experimentally in a lab‐scale spouted bed. Experiments were carried out at different operating conditions, and the effect of inlet air temperature and its flow rate, bed height (initial mass of wet particles) and average diameter of particles were examined on performance of dryer and rate of drying. The obtained experimental results were fitted by an exponential form equation to model the drying kinetic behaviour of green peas in a spouted bed. The fitting parameters are presented in the form of mathematical correlations as a function of operating parameters. As expected, it was found that by increasing inlet air temperature and air‐flow rate, the rate of drying increases, but by increasing the bed height and diameter of particles, the rate of drying decreases. The results can help the design engineers to choose the optimum drying conditions for industrial applications.     

Conical spouted bed drying of Baker's yeast: Experimentation and multi-modeling

Baker's yeast drying experiments in a conical spouted bed are used to characterize the effects of operating conditions on drying behavior. A novel multiscale model, describing Baker's yeast drying in a conical spouted bed, is presented; it is based on an intrinsic drying model developed for a single pellet, combined with a gas–solid flow model developed for a conical spouted bed. The resulting phenomenological model, which has only one adjustable parameter, is in good agreement with the experimental results. The model is capable of adequately predicting the drying rate of Baker's yeast pellets during the entire drying period in a conical spouted bed: from the beginning, where the water removal rate is limited by the air saturation with vapor during its residence time in the bed; to the end, where the water removal rate is dictated by internal resistance within the yeast pellets.The quality of dried Baker's yeast was characterized by measuring the gassing power in bread dough. This parameter was monitored during the conical spouted bed drying experiments. It was found that yeast degradation is linked to intracellular water removal (type D, end of the drying below a moisture content of around 0.5 (d.b.)) and it is mostly the rate of this water removal that controls the final quality of the product. Intercellular water removal (type E, beginning of the drying) was found to have no significant influence on yeast degradation. In all the cases, degradation is amplified when solid temperature is higher than 40 °C.     

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...     

Physical properties of parboiled wheat and bulgur produced using spouted bed and microwave assisted spouted bed drying

The main objective of this study was to compare the spouted bed and microwave assisted spouted bed drying on affecting physical properties of parboiled wheat and bulgur. Drying was performed at different temperatures (50 °C, 70 °C, 90 °C) and microwave powers (288 W, 624 W). Bulk and apparent density, bulk and apparent porosity, sphericity, color, microstructure and pore size distribution of parboiled wheat were investigated after drying. Yield and water absorption capacity were determined in bulgur samples. The effect of air temperature on physical properties of product except color was not significant in spouted bed drying. More porous structure was observed in wheat samples dried in microwave assisted spouted bed compared to air dried ones. Sphericity and bulk density were higher when high temperature was combined with high microwave power. In microwave assisted spouted bed drying, similar yield value but lower water absorption capacity of bulgur were observed as compared to spouted bed drying.     

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.     

The thermal disinfestation of wheat in a spouted bed

Batches of wheat infested with all stages of Rhyzopertha dominica were heated in a 300 mm dia spouted bed fitted with a draft-tube to control grain and air flow paths. This apparatus combines features of pneumatic and packed bed systems. For a 16 kg batch of wheat spouted with 0.07 kg s⁻¹ of air the time to achieve 99.9% mortality (LT_99.9) decreased from 13.6 to 2.6 min as inlet air temperature was increased from 80 to 180°C. LT_99.9 increased with increase in bed mass and decrease in air flow rate, and was sensitive to the type and axial position of the draft-tube. Bed temperatures corresponding to LT_99.9 were in the range of 60–66°C depending on operating conditions. Some mechanical kill was also detected. Thermal contact efficiencies varied from 45 to 80% and were sensitive to operating and design parameters. The practical considerations for the scale-up of spouted bed disinfestors are discussed.     

DRYING METHODS AND QUALITY OF SHRIMP DRIED IN A JET-SPOUTED BED DRYER

The objective of this study was to experimentally investigate the effects of various parameters, i.e., size of shrimp, level and pattern of inlet drying air temperature, on the drying kinetics and various quality attributes of dried shrimp viz. shrinkage, rehydration ability, texture and color during drying in a jet‐spouted bed dryer. It was found that the use of a constant inlet air temperature of 100C yielded dried shrimp of the best quality in terms of low percentage of shrinkage, high percentage of rehydration, low maximum shear force and high value of redness compared to shrimp dried using other conditions. A simple mathematical model that enables prediction of the drying behavior of shrimp in a jet‐spouted bed dryer has also been developed.     

Microwave Finish Drying of Diced Apples in a Spouted Bed

The combination of a spouted bed with microwave heating to improve heating uniformity was evaluated. Experiments were performed on a laboratory system in which evaporated diced apples of about 24% moisture were dried to about 5% at 70°C air temperature using four levels of microwave power density (0 to 6.1 W/g). With the combination method, temperature uniformity in diced apples was greatly improved as compared to that with a stationary bed during microwave drying. Products had less discoloration and higher rehydration rates as compared to conventional hot air drying or spouted bed (SB) drying. Drying time could be reduced by >80% compared with SB drying without microwave heating.     

红外—喷动床联合干燥设备研制与分析

为较好地解决单一红外干燥均匀性差的问题,利用红外加热高效节能的特点,结合喷动床流动性好、传热均匀的特点,设计了红外联合喷动床干燥设备。该装置包括喷动床干燥系统、红外辐射加热系统、回风式空气调节系统、动力循环系统和控制系统等。并以新鲜毛豆为物料,对该装置干燥均匀性和产品品质进行试验验证。结果表明,单一红外干燥耗时270 min,而红外—喷动床联合干燥耗时160 min,与单一的红外干燥相比,红外—喷动床联合干燥时间缩短了40.7%;同时,红外—喷动床联合干燥设备减轻了毛豆仁干瘪皱缩现象,使干制品具有较好的豆香味和感官品质。     

Image analysis and quality attributes of malting barley grain dried with infrared radiation and in a spouted bed

The impact of drying two spring barley cultivars (Mauritia and Prestige) in a spouted‐bed and in infrared radiation (IR) dryers on grain dimensions, colour, pigment content, vitality and malt quality was investigated. The results indicate that the investigated drying methods led to kernel dimension changes. Kernel shrinkage was typical of spouted bed drying, while kernel expansion was observed after IR drying at the intensity of 900 W m^?2. An increase in the intensity of yellowness (b*) on the surface of dried grain and a decrease in the yellowness intensity of kernel cross‐section were also observed. The aforementioned changes were associated with the decomposition of carotenoids (endosperm colour) and reduction of soluble proanthocyanidin and total phenolic compounds (surface colour). The drying processes also lowered germination energy and capacity, in addition to susceptibility to moisture diffusion into the endosperm. These adverse results were cultivar dependent and affected the quality of malt and wort only to a limited extent. The main changes were an increase in the Kolbach index in malt from Mauritia cv., and a fluctuation of the diastatic power of malt that did not exceed ±3%. Generally, drying of barley grain in spouted bed should be conducted at an inlet air temperature of 40 °C and using an IR drier at a radiation intensity of 600 W m^?2.     

MICROWAVE and SPOUTED BED DRYING of FROZEN BLUEBERRIES: the EFFECT of DRYINGAND PRETREATMENT METHODS ON PHYSICAL PROPERTIES and RETENTION of FLAVOR VOLATILES

Frozen blueberries (Vaccinium corymbosum L cv. 'Elliott') were dried in a microwave and spouted bed combined dryer (MWSB) at 70C air temperature and 3.7 W/g microwave power (wet material). the effect of pretreatment using a 2.5% Ethyl Oleate & 0.2 NaOH dipping solution followed by sucrose osmotic treatment was investigated. the drying kinetics of MWSB drying was compared with spouted bed (SB) drying with dipping treatment, and with tray drying. the rehydration ratio, the color, and the bulk density of MWSB dried blueberries were compared with those of freeze, tray, and SB drying. the drying time needed to reduce blueberry moisture content from 82.5% to 15% (wet basis) using MWSB drying was 1/19 and 1/24 (with and without pretreatment) of the time for tray drying. the MWSB drying resulted in a low bulk density and more reddish and less blue color compared with other methods. MWSB dried frozen blueberries exhibited a higher rehydration ratio in short soaking times. Analysis of flavor volatiles by GC/MS identified ten heat-generated compounds. Microwave heating generated three unique flavor compounds (2-Butanone, 2-methyl butanal, and 3-methyl butanal). Freeze-dried frozen blueberries lost several flavor compounds including the typical blueberry aroma, the 1, 8-Cineole.     

Low-cost drying methods for developing countries

Low-cost drying technologies suitable for rural farming areas are presented. Some of the important considerations with regard to their suitability include: 1. Low initial capital; 2. easy-to-operate with no complicated electronic/mechanical protocol, and 3. effective in promoting better drying kinetics. The drying technologies that were selected include fluidized bed, spouted bed, infrared, solar, simple convective and desiccant drying. A brief introduction on each drying technology has been presented followed by some technical details on their working operations. Examples of farming crops suitable for the employment of individual drying technology are provided to illustrate their potential application in agricultural product drying.     

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.     

Protein quality of dried enzymatic hydrolysate from anchovy produced in a spouted bed of inert particles

The anchovy (Engraulis anchoita) is a pelagic fish and due to its abundance in South America shows a sustainable exploitation. The enzymatic hydrolysis of anchovy protein associated to the drying technique in spouted bed was analysed in order to obtain products with the best characteristics. The drying conditions were inlet air temperature, concentration and flow rate of suspension. The degree of hydrolysis of the anchovy suspension was of 3.8%, and its available lysine and specific antioxidant activity were of 86 g kg^?1_protein and 4.31 mm _DPPH kg^?1 min^?1, respectively. In spouted bed drying, the lowest reduction in available lysine (9%) and loss of specific antioxidant activity (8%) were found at 90 °C, and suspension concentration and flow rate of 65 g L^?1 and 200 mL h^?1, respectively. The dried product was characterised as a protein source of high biological value due to the essential amino acids profile.     

基于BP神经网络预测红外-喷动干燥带壳鲜花生水分比

为实现带壳鲜花生红外-喷动干燥过程中水分比的预测,本实验探究了不同干燥温度（55、60、65 ℃和70 ℃）、进口风速（16、17、18 m/s和19 m/s）和助流剂质量（1.0、1.5、2.0 kg和2.5 kg）对带壳鲜花生干燥时间和干燥速率的影响,建立了输入层为干燥温度、进口风速、助流剂质量和干燥时间,隐含层节点数为11,输出层为带壳鲜花生水分比,拓扑结构为“4-11-1”的BP神经网络模型。结果表明：干燥温度和进口风速是影响带壳鲜花生水分比的主要因素,增加进口风速和提高干燥温度能有效缩短带壳鲜花生的干燥时间,提高干燥效率。采用Levenberg-Marquardt（L-M）算法为训练函数,选择tansig-purelin为网络传递函数,经过有限次训练得到的BP神经网络模型,其水分比预测值与实验值之间的决定系数R2为0.99,均方误差为0.02,水分比预测结果相较于传统经典数学模型准确且迅速。本研究建立的BP神经网络模型可为带壳鲜花生在红外-喷动干燥过程中的水分比在线预测提供理论依据和技术支持。     

谷物干燥方法的研究

介绍了谷物的各种干燥技术和方法,以及干燥方法的研究进展。目前谷物干燥方法主要有微波干燥、红外线辐射干燥、顺溜干燥、流化床干燥、低温真空干燥、热风干燥和喷动床干燥。     

Studies on different combined microwave drying of carrot pieces

Three different combined microwave (MW) drying methods were compared, namely microwave‐assisted vacuum drying (MWVD), microwave‐assisted freeze drying (MWFD), microwave‐enhanced spouted bed drying (MWSD), in terms of drying rate, drying uniformity, product colour, rehydration ratio, retention of β‐carotene and vitamin C, and energy consumption. The drying rate of MWVD and MWSD were much faster than that of MWFD. The largest drying rate was obtained in MWSD with 3.5 W g^?1. In general, the colour of MWSD products was very uniform. Rehydration ratio of MWFD carrot pieces was almost the same as the freeze‐dried (FD) products and better than MWVD and MWSD products. In addition, the highest retention of carotene and vitamin C was observed in MWFD carrot pieces. No significant differences were observed in carotene and vitamin C between MWVD and MWSD products. However, the energy consumption in MWFD was the highest.     

Hydrodynamic characteristics of a pulsed spouted bed of food particulates

Pulsed spouted bed has been developed to offset some limitations posted by a conventional spouted bed and some other modified spouted beds that allow an intermittent operation, which has proved to offer many advantages over continuous spouting. However, detailed hydrodynamic behavior of a pulsed spouted bed is not yet available. The present study thus investigated the effects of various parameters, i.e., type of material, pulse frequency and static bed height, on the spouting behavior as well as other bed basic hydrodynamic characteristics viz. maximum spoutable bed height, maximum pressure drop (ΔP_max), steady spouting pressure drop (ΔP_s) and minimum spouting velocity (U_ms). Soybean, whole-shelled peanut and French bean were used as test materials to represent food particulates of different characteristics. Empirical correlations that can be used to predict the tested hydrodynamic behavior of the pulsed spouted bed were also developed.     

Dehydration and Separation of Grape Pomace in a Fluidized Bed System

Grape pomace components (seed and skin) were separated in a fluidized bed system based on their aerodynamic behavior. The Weibull equation was used to explain the elutriation history. Seed dehydration was characterized by a first period of constant drying rate and a second period in which drying rate decreased following Fick's liquid molecular diffusion model. The order of magnitude of heat and mass transfer parameters, both internal and external, was similar to those reported in the literature.