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.     

Improving head rice yield of glutinous rice by novel parboiling process

Most commercial parboiled rice is produced from high-amylose content rice. Glutinous rice, which is lacking in amylose content, is generally consumed in Southeast Asian countries. Rare study of parboiling glutinous rice has been observed. In this study, glutinous rice was improved in head rice yield by a novel parboiling process. Two rough glutinous rice, rice department 6 (RD6) and black glutinous rice (BGR) cultivars, were soaked in hot water at 70?±?5°C for 3?h. The ricer 3moisture content after soaking was 50–52% (d.b.), it was dried with hot air and superheated steam (SHS) at 110, 130, and 150°C in a fluidized bed dryer. The results show that SHS at all drying temperatures can improve the high head rice yield in both parboiled glutinous rice cultivars better than hot air drying. Higher temperature drying caused L* value to decrease but the b* value increases in RD6, whereas in BGR, all color values decreased and ΔE* was increased when the drying temperature increased. Increasing drying temperature presented a softer texture of both glutinous rice cultivars. Upper 130°C, completed gelatinization of both varieties can be obtained and seen by scanning electron microscope and differential scanning calorimeter (DSC). This technique of using high-temperature fluidized bed drying can produce completely parboiled glutinous rice in a single process instead of two conventional processes, steaming and drying, in series.     

Influence of hot air fluidized bed drying on quality changes of purple rice

The influence of drying using a fluidization technique on the quality of purple rice was investigated in this study. The results demonstrated that the initial moisture of rice was 28.3% dry basis (db). Compared to the sun-dried or reference purple rice samples, the influence of drying at temperatures ranging from 100 to 150°C did not affect the quality of color, anthocyanin content, total phenolic content, or antioxidant activity. At this initial moisture level, samples should be dried at 150°C air because such temperatures yield the highest drying rate. Drying at this temperature also causes an increase in the head purple rice yield because of the gelatinization of starch. In the case of an initial moisture content of 33.3% (db), the drying temperature should not exceed 130°C.     

Effect of tempering approach following cross-flow drying on rice milling yields

Abstract

Three tempering approaches were followed after drying rough rice at 16.3% and 20.5% initial moisture contents (IMCs) using 57?°C/13% RH air at an airflow of 0.56 (m³/s)/m² for 30, 60, and 90?min in an experimentally simulated cross-flow drying column. For the longer drying durations, post-tempering head rice yields were consistently less when the interstitial air from rice from different cross sections of the drying column was allowed to “interact” during tempering than when the rice from these different cross sections was tempered separately; this effect was more prominent at the greater rice IMC. RH of the interstitial air during tempering was measured and used to estimate the minimum tempering durations required for the different tempering approaches.     

Evolution of mechanical properties of parboiled brown rice kernels during impinging stream drying

Information on mechanical properties of parboiled brown rice kernels upon impinging stream drying, which is important for effective control of kernel fissure and head rice yield, is reported. Experiments were performed at the drying temperatures of 130, 150, and 170°C; inlet air velocity of 20?m/s; impinging distance of 5?cm and paddy feed rate of 40?kg_{dry_paddy}/h. Parboiled paddy was dried for up to seven cycles. Between each drying cycle, the paddy was tempered for a period of either 0 (without tempering) or 30?min. The moisture evaporation rate was noted to be very high during the first two drying cycles and rapidly dropped in the later drying cycles. When tempering was included after a particular drying cycle, the drying rate in a subsequent cycle was higher than without tempering. At the kernel moisture contents immediately after drying of 25.3–47.5% (d.b.), the drying temperature and existence of tempering did not affect the mechanical properties although microcracks were formed in the kernels. However, both factors played a more important role on the mechanical properties when the kernels were evaluated at 16% (d.b.). The head rice yield correlated well with the tensile strength of the kernels.     

Effects of operating parameters of impinging stream dryer on parboiled rice quality and energy consumption

Abstract

It is very important to know how operating condition of a coaxial impinging stream dryer affects the drying time, parboiled rice quality and energy consumption. The drying temperature, parboiled paddy feed rate, drying air velocity and impinging distance were experimentally investigated. Increases in drying temperature and air velocity and a decrease in paddy feed rate provided higher evaporation rate whilst impinging distance, ranging from 5 to 13?cm, did not affect the evaporation rate. Collision between kernels within the impinging zone caused the hull’s lemma splitting from the kernel and the percentage of the split kernel strongly depended on the air velocity and feed rate. The acceleration in the rate of drying by changing the above operating parameters did not affect the head rice yield. In addition, the collision of kernels also did not influence the head rice yield since the mechanical properties of rice are strengthened during steaming step in the parboiling process. However, the change of head rice quality was only governed by the moisture content after drying. The total energy consumption including electricity and heat was strongly depended on the air velocity and feed rate whilst it was slightly changed with the drying temperature. From the present study, it was recommended that the parboiled paddy should not be dried below 25% d.b. and the highest temperature that could possibly be used was 190?°C and the inlet air velocity should not be below 15?m/s.     

Fluidization characteristics of rice husk in a bubbling fluidized bed

An investigation was carried out in a circulating fluidized bed to explore if rice husk could be fluidized without mixing it with any foreign solids. Experimental results indicate that bed cross‐section has an important influence on the fluidization characteristics of rice husk. Larger the cross‐section, easier it is to fluidize the husk without slugging. Particle size, sphericity, bulk density, and transport velocity of husk were measured. The riser was operated under bubbling bed regimes. Efforts were made to measure the minimum fluidization velocity by varying the bed depth and cross‐section.     

Influence of postharvest drying conditions on resistant starch content and quality of non-waxy long-grain rice (Oryza sativa L.)

This study investigated the effect of postharvest drying conditions on resistant starch (RS) content and quality of rice. Paddy was subjected to hot-air drying at 40, 65, 90, and 115°C, and sun drying. Drying conditions altered head rice yield, RS and overall firmness of cooked rice, and some pasting properties of rice flour. No significant variation in RS of uncooked rice and surface firmness of cooked rice was observed among the samples. However, RS of cooked rice from sun drying was lower than the others. Higher temperature in hot-air drying resulted in a slightly increase in RS of cooked rice.     

Stress fissuring and process duration during rough rice convective drying affected by continuous and stepwise changes in air temperature

During rough rice drying, gradients of moisture content and glass transition temperature cause thermal and mechanical stresses inside the kernel. These stresses eventuate to kernel fissuring during the milling process. In this study, convective drying of Hashemi (long grain) rough rice was applied to investigate the effect of continuous and stepwise changes in air temperature on stress cracking index and process duration. Toward this objective, the concepts of glass transition and analysis of moisture contents distributions within the rice kernel were determined through a numerical modeling of mass transfer. For stepwise temperature change, the drying experiments were conducted at temperatures above the glass transition temperature. Results indicated that the stress cracking index under stepwise temperature change conditions (i.e., within the rubbery state) was reduced compared to the continuous mode probably due to a drip in the moisture content gradients created inside the kernels during the drying process. Moreover, the drying duration significantly was shortened when the kernel was dried within the rubbery state due to faster diffusion moisture within the kernel.     

Effect of air velocity in dehumidification drying environment on one-component waterborne wood top coating drying process

In this study, the effect of air velocity in dehumidification drying environment on one-component waterborne wood top coating drying process is analyzed by drying time and moisture content and surface temperature of coating, in which air temperature is 35°C and relative humidity is 50%, and the air velocity is the only change parameter, varying from 0.2 to 1.2?m/s. It is found that drying time of top coating shortens and moisture content of top coating decreases with increasing air velocity. Surface drying time is about 15?min, hard drying time 21?min, and sanded drying time 37?min. To accelerate the drying speed, the air velocity is increased to more than 0.4?m/s. Moisture content of top coating is 58.2% during surface drying, 31.4% during hard drying, and 21.9% during sanded drying time. An infrared thermometer is used to measure the surface temperature of coating. Surface temperature of top coating is 30.0°C when it is dried to the surface drying degree, 33.5°C when the top coating is dried to the hard drying degree, and 34.6°C when the top coating is dried to the sanded drying degree. The drying degree of coating can be judged from the drying time and surface temperature and moisture content of coating. The drying degree of top coating is better when surface temperature is higher and the moisture content is lower.     

循环热风低温干燥系统湿空气冷凝特性分析

基于能量梯级利用热力系统耦合理论,集成了一种适合热敏性农副产品烘干的新型空气干燥循环系统,系统可得到热敏性干燥产品,同时回收湿空气冷凝废热用于有机朗肯循环(ORC)系统对外做功。对关键部件湿空气冷凝器建立传热传质数学模型并经实验验证,考察了关键操作参数对系统脱水速率及节能效果的影响。结果表明,湿空气湿度是影响该系统凝水和节能的最关键参数,该系统凝水及节能特性均随湿空气湿度提高而改善;当干燥箱出口湿空气含湿量温度一定时,新型空气干燥循环凝水量主要受到干燥箱出口空气流量的影响,系统的凝水量和换热量均随湿空气质量流量增加先增加后降低,在0.10~0.15 kg/s出现极大值;系统净输出功随ORC底循环蒸发温度提高显著增加。本系统下的热敏性农副产品烘干建议选择低空气流速、低烘干温度,推荐的ORC底循环蒸发温度为313~323 K。     

Study of the drying process of ginger (Zingiber officinale Roscoe) slices in microwave fluidized bed dryer

ABSTRACT

To research about the temperature and moisture characteristics of ginger slices in microwave fluidized bed drying (MFD), some microwave drying experiments in different powers and hot-air drying experiment were used, and the drying quality and moisture drying curves were studied in contrast, finding MFD with advantages such as good quality and high efficiency. In order to understand the water flow characteristics of ginger slices in MFD, low nuclear magnetic resonance was used to detect the materials in different drying stages, and it was found that free water (FW), immobilized water (IW), and bond water (BW) could be converted to the other forms, especially the form that combined with the dry matter is much firmer. FW is the main water state in fresh ginger slices and converts to the IW quickly in the beginning stage, and then both FW and IW decreased until the final stage is reached. Finally, the content of BW increased, and the material can be stored safely. Gingerol is the main flavor component of ginger, and it was detected through LC-20A high-performance liquid chromatography; it was found that the content of 6-gingerol, 8-gingerol, and 10-gingerol increased in various drying processes, especially 10-gingerol that has a positive role to protect the taste of the ginger.     

A FEM model of conventional hot dipping coating process by using a fluidized bed

A FEM model of a conventional hot dipping fluidized bed (FB) coating process on a low carbon steel rod using a PPA thermoplastic powder was developed. Two computational domains, the former for the metal substrate and the growing coating and the latter for fluidized bed emulsion nearby the metal substrate were set. A novel recursive procedure was employed to solve the ‘coupled’ thermal problem. Besides, realistic values of polymer thermal properties according to temperature as well as the whole curve of polymer enthalpy were input to the model so as to increase its reliability.

As a result, consistent trend of coating thickness and growth rate according to dipping time with experimental data and theoretical considerations were calculated. Moreover, the calibration procedure of FEM model took to realistic values of heat transfer coefficient according to preheating temperature of substrate as the comparisons with available experimental data confirm. At last, dimensionless analysis stated once more the FEM model reliability by comparing the numerical findings with those of pioneer models available in literature.     

Preparation and application of potato flour with low gelatinization degree using flash drying

A novel processing method of potato flour with a low starch gelatinization degree was realized by flash drying technique. Starch gelatinization degree, pasting properties, thermal characteristics, and morphological features between commercial potato flours (commercial potato flake and commercial potato granule) and flash-dried potato flour were analyzed and compared. Results showed that the gelatinization degree of flash-dried potato flour (14.52%) was reduced by nearly 80% than the commercial potato flours (about 95%). Typical viscosity profile, enthalpy value, and morphology features of flash-dried potato flour were retained maximally through an optimized processing of flash drying. The gelatinization temperature and pasting viscosity of flash-dried potato flour were increased significantly than the commercial potato flour. Besides, the intact morphological structure of flash-dried potato flour granules were kept due to the processing of flash drying. By utilizing the low gelatinization degree of flash-dried potato flour, desirable potato noodles were prepared with the ratio of potato flour up to 50%. Textural characteristics and cooking performance such as broken rate and cooking loss of flash-dried potato noodles were superior to these of the commercial potato flours (in the same amount) added noodles.     

气相流化床工艺冷凝态操作冷剂浓度的控制

分析了冷凝态操作中异戊烷浓度对露点温度和反应负荷的影响,通过理论计算,总结生产经验得出了确定露点温度和反应负荷的方法以及冷凝态操作时生产负荷控制的最佳范围。     

Evaluation of the air-borne ultrasound on fluidized bed drying of shelled corn: Effectiveness,grain quality,and energy consumption

The objective of the study was to investigate the influence of high power ultrasound on a laboratory-scale fluidized bed shelled corn dryer. The drying time, moisture content variation, specific energy consumption, and quality parameters including ultimate compressive strength, toughness, shrinkage and color of corn kernels were investigated. Furthermore, artificial neural network (ANN) simulation models were developed for predicting the drying variables. Machine vision techniques were used to determine color and shrinkage as qualitative indices. Results showed that the lower frequencies had better penetrations at lower temperatures and cause a significant reduction in drying time. In addition, the ultrasound application led to reduction of ultimate compressive strength and toughness of the dried samples although ultrasound has nonthermal character as the subsidiary factor, it plays an important role in shrinkage and color specification. Based on error analysis results, the prediction capability of ANN model is found to be reasonable for the developed models. Application of ultrasound significantly decreased the specific energy consumption of drying process at the optimal drying condition.     

改造干燥工艺 提高氯气质量

介绍了填料干燥塔串联、内溢流式泡沫干燥塔与填料塔串联、外溢流式泡沫干燥塔与填料塔串联等数次改造过程。采用外溢流式干燥塔与填料塔串联的工艺,干燥后氯气温度上升6～8℃,氯中含水在10     

Effect of process parameters on circulating fluidized bed coal gasification using 3D full-loop CFD simulation

This article presents a 3D full-loop computational fluid dynamics (CFD) simulation of a circulating fluidized bed gasifier (CFBG). The simulation results are validated against the experimental data and found to be in good agreement. Thereupon, the effect of the process parameters, ie, temperature, pressure, air/coal (A/C) ratio, and steam/coal (S/C) ratio, on the performance of the gasifier is analyzed. The effect of temperature on the hydrodynamics was found to be small. The CO and H₂ increase, whereas the CO₂ and H₂O decrease with an increase in temperature. While the effect of pressure on the outlet species mole fraction is negligible, the gas and solid axial velocity decrease with an increase in pressure. With an increasing A/C ratio or decreasing S/C ratio, the combustion products (CO₂ and H₂O) increase, whereas the gasification products (CO and H₂) decrease due to the increase in the O₂ concentration. In addition, temperature increases with an increase in the A/C ratio or a decrease in the S/C ratio. The feed velocity increases with an increasing A/C or S/C ratio, and, accordingly, the pressure increases and bed height decreases. The CH₄ decreases in all of the cases as it is being consumed in gasification as well as combustion reactions.     

Evaluation of quality properties and water mobility in vacuum microwave-dried carrot slices using pulse-spouted bed with hot air

Fried carrot slices feature high fat content to impair people healthy. To resolve this issue, microwave hot air-assisted pulse-spouted vacuum drying (MHAPSVD) has been designed using microwave vacuum dry on pulse-spouted bed with hot-air steam. Dying characteristics, moisture mobility and qualities of carrot slices had been confirmed after dying using 915?MHz microwave generator. Experiment was carried out at 3 W/g, 90?°C air stream, 0.08?MPa vacuum pressure and 2?s pulse interval for drying time of 10–80?min. The quality properties of color, odor, rehydration ratios, shrinkage ratios as well as tastes in 70?min drying are found to be suitable for a snack food. High moisture stability of carrot slices was achieved after 50?min. Free water decreased dramatically from start to 20?min and bound water declined sharply from 20 to 50?min. MHAPSVD could be a high efficient and quality drying technology for crisp product.     

Separation of conglomerate forming enantiomers using a novel continuous preferential crystallization process

Providing enantiomerically pure products is of key importance in the fine chemicals, food, and pharmaceutical industries. A continuous preferential crystallization process is presented that allows the separation of conglomerate forming enantiomers in a stable, robust, and flexible way. This is achieved by coupling two continuous crystallizers by exchanging their clear liquid phases. Each crystallizer is connected to a suspension mill responsible for in situ seed generation through particle breakage. The dynamic and steady‐state behavior of this process is extensively analyzed for racemic feed streams through process simulations, and parameter regions, which yield pure enantiomers in both crystallizers, are identified. For enriched feed streams, it is further shown when this novel flow sheet is capable of outperforming an ideal batch process in terms of solvent consumption per unit mass of desired enantiopure product produced. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2810–2823, 2015