Effects of drying conditions in hybrid dryer on the GABA rice properties

In this study, pre-germinated rough rice was dried under various conditions using a hybrid dryer that incorporated heat pump dryer with fluidized bed drying (FBD) system in order to compare with the single-stage drying by hot air dryer. The main objective was to investigate the effect of drying conditions on the cooking and physical properties, nutrients and sensorial qualities of GABA rice products. It appeared that the FBD at 100–140 °C led to noticeable increase of head rice yield. The germination process caused the decline of gelatinization enthalpy of brown rice flour, the change of pasting properties, the reduction of cooking time and escalation of the total phenolic content, antioxidant activity and GABA content. The FBD at higher temperature significantly raised the degree of starch gelatinization and caused longer cooking time, higher hardness and adhesiveness of cooked GABA rice. Three-stage drying comprising FBD at 60 °C for 10 min in the first stage followed by FBD at 100 °C in the second stage and then heat pump drying at 45 °C together with tempering step between drying stages was recommended due to its superior GABA rice product quality.     

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.     

基于遗传算法的烘缸干燥曲线的参数优化

在保证纸张质量的前提下,为了减少纸机干燥部的蒸汽消耗,可通过建立纸页干燥过程数学模型对干燥曲线进行参数优化,使用遗传算法完成寻优过程,并根据优化结果调整干燥曲线。实际运行结果表明,干燥过程能耗明显下降,纸张物理性能有所提高。     

Development of Mobile Dryer for Freshly Harvested Paddy

Presently, due to an increase in usage of large scale mechanical threshers and combine harvesters, moisture content of freshly harvested paddy is being high as much as 18-24%. The mechanical threshers or combine harvesters with elevated capacity enable for both harvesting and threshing at once. Thus the paddy harvested all over persists with high moisture content that affects adversely in unit operations of paddy processing such as cleaning, storing, and milling. The research was conducted to overcome this problem by developing a mobile paddy dryer that can be used at field level for freshly harvested paddy. A mobile dryer, one ton capacity, was developed and tested for drying freshly harvested paddy. The performance of the mobile dryer was evaluated in terms of overall thermal efficiency, heat utilization factor, coefficient of performance, total heat efficiency and head rice yields. The overall thermal efficiency of this dryer was 46.83%. The average heating efficiencies namely heat utilization factor and total heat efficiency were 0.82 and 0.72 respectively. The coefficient of performance of the developed dryer was 0.18. The head rice yields of freshly harvested paddy after drying at 60 °C air temperature was of 73.78%. The overall drying performance of the dryer was found to be good.     

Drying characteristics and quality of taegeuk ginseng (Panax ginseng C.A. Meyer) using far‐infrared rays

The purpose of this study is to investigate the drying characteristics of taegeuk ginseng using a far‐infrared dryer. The dryer used for this experiment can control the drying parameters such as far‐infrared heater temperature and air velocity. The far‐infrared drying tests of taegeuk ginseng were performed using large, medium and small ginseng at an air velocity of 0.6 m s^?1, and drying chamber temperatures of 45, 55 and 65 °C. The results were compared with those of the hot‐air drying method. The drying characteristics were analysed based on factors such as drying rate, colour changes, internal tissue structure of ginseng, saponin contents and antioxidant activities, and energy consumption. In general, the hot‐air drying time was 3–3.5 days longer than that of far‐infrared drying under the same conditions. The colour changes of far‐infrared drying were also smaller than that of hot‐air drying. Far‐infrared dryer required less energy consumption about 9.67–14.8% less than that required by hot‐air drying. At the same time, the saponin and polyphenol contents of taegeuk ginseng subjected to far‐infrared drying were 1.01 mg g^?1, 7.81 mg/100 g higher than that subjected to hot‐air drying, respectively. The results showed that the far‐infrared drying increases the capacity and quality of taegeuk ginseng.     

基于工艺流程的纸机干燥部建模与模拟

基于三段通汽式干燥部工艺流程,在“输入已知、输出未知”和“先烘缸、再通风、后纸张”的原则指导下,以烘缸组为最小建模单元,根据序贯模块法的基本思路,构建了纸机干燥部的静态模型。以某新闻纸机干燥部为对象进行模拟,给出了进出各模块的物流和能流信息,模拟结果与该纸机实际运行情况基本一致。该模型符合纸机干燥部工艺流程,可以用来模拟各模块之间的物流和能流信息,便于为干燥部用能分析提供依据。     

Effect of superheated-steam drying compared to conventional parboiling on chalkiness,head rice yield and quality of chalky rice kernels

Four rice cultivars (Ayutthaya 1, Khao Bahn Nah 432, Plai Ngahm Prachin Buri, and Prachin Buri 2) that usually have a major problem with chalkiness were processed by applying superheated-steam drying and conventional parboiling methods. The main objectives were: (1) to determine the possibility of applying superheated-steam drying to solve the chalkiness and low head rice yield problems and (2) to compare the properties of rice produced using superheated-steam drying and the conventional parboiling process. Both the initial moisture content and superheated-steam drying temperature significantly affected head rice yield. The higher moisture helped to increase starch gelatinization leading to a stronger rice structure and subsequently an increased head rice yield. The rice samples dried in the superheated-steam dryer using an initial moisture content of paddy at 32% w.b. for 6 h under a steam pressure of 1.2 bar and at three drying temperatures (120, 140, 160 °C) had higher milling quality than the conventionally parboiled rice samples. The darker color of the superheated-steam-dried samples was their main drawback. Both parboiling and superheated-steam drying could clearly lessen the percentage of chalky rice kernels compared to the raw paddy. The parboiled rice and superheated-steam-dried rice had more nutrients than normal white rice.     

Exergy,energy and economic analysis of a V-groove assist rotating tray type solar cabinet dryer for drying potato chips

In this present work we have studied the exergy, energy and economic performance of a V-grooved type air collector with rotating trays type of solar cabinet dryer for drying potato chips in the sunny days of winter season at Bhubaneswar (20.2961° N, 85.8245° E), Odisha. The obtained results from this experiment were also compared with the performance of a flat plate air collector with rotating trays used in the same dryer. The average energy efficiency of the solar air collector (SAC) and drying chamber (DC) was found to be 73.3% and 24.8% in case of V-grooved and 60.1% and 19.3% in case of plane collector respectively. The average exergy inflow, outflow, loss and efficiency of the drying chamber in case of V-grooved collector was found as 19.7 W, 11.82 W, 7.88 W and 58.14% where as it was 22.3 W, 12.96 W, 9.34.88 W and 56.12% in case of plane collector respectively. Similarly the average exergy inflow, outflow, loss and efficiency of the SAC in case of V-grooved was found as 845 W, 20.1 W, 824.9 W and 1.99% where as it was 830 W, 22 W, 808 W and 2.28% in case of plane collector respectively. The average exergy and energy efficiency of the V-grooved type chamber are found to be 3.47% and 22.17% higher respectively as compared to plane collector. The air temperature at the inlet and outlet of the SAC and DC mainly affects the exergy value.     

Drying performance and economic analysis of novel hybrid passive-mode and active-mode solar dryers for drying fruits in East Africa

In East Africa, post-harvest loss of fresh perishable fruits is enormous, causing recurrent seasonal deficits. In response, a modified passive-mode hybrid solar dryer hereafter called; ‘an Improved Solar Dryer (ISD)’, was developed as a potential low-cost technology alternative for drying fruits in Uganda. An improved PV-assisted hot air dryer using active-mode hybrid solar dryer hereafter called; ‘Solar Photovoltaic and Electric (SPE)’ was also fabricated. The ISD dryer utilises freely-available solar energy to dry the produce. In contrast, the SPE dryer uses both solar photovoltaic and electricity sources. In this study, the drying performance of the ISD and SPE dryers were performed and compared to that of the traditional open sun drying (OSD) method. Relative to the OSD method, the economic performance of the ISD and SPE dryers was analysed. The drying performance results show that the mean drying air temperatures achieved by the ISD and SPE dryers were 31.9 and 41.1 °C respectively; relative to the 27.6 °C for the OSD method. On average, the thermal energy attained by the ISD and SPE dryers were 3551 and 5757 Watts (W) respectively, as compared to 2952 (W) obtained for the OSD method. It took the ISD and SPE dryers 10 and 18 h to effectively dry the fruit (pineapple) products, respectively as opposed to the 30 h taken by the OSD method. The results confirm the superior performance of the ISD and SPE dryers than the OSD method. Results for the economic performance analysis show more reduced costs of drying the products using the ISD than the SPE dryer. Similarly, the pay-back period for the ISD was 2.4 times shorter than that of the SPE dryer. Joint results for economic analysis and drying performance confirm the ISD as a better drying technology than the SPE dryer in the context of the resource-constrained farmers/agro-processors without electricity in Uganda and East Africa.     

Effects of fluidized bed drying temperature and tempering time on quality of waxy rice

Waxy rice, which is soft and sticky in nature, can be used as a raw material to produce many food products. After being harvested, high-moisture waxy paddy must be dried to appropriate moisture content to prolong its storage life and to achieve higher head rice yield. Fluidized bed dryer could be used to dry waxy rice at high-temperature. However, due to the high heat and mass transfer rates during drying, stresses are generated in a rice kernel, leading to crack and low head rice yield. Tempering is thus recommended to reduce the moisture-induced stresses in the kernel after rapid drying. In this study, the effects of fluidized bed drying temperature (90, 110, 130 °C) and tempering time (30–120 min) on the quality of waxy rice, i.e., head rice yield, thermal properties, pasting properties, color, translucent kernel and microstructure, were investigated. The results showed that head rice yield of waxy rice after drying was significantly lower than that of the reference sample even when tempering was performed. Higher drying temperatures led to higher head rice yield while the tempering time did not have any effect on the head rice yield except when the drying temperature of 90 °C was used. Drying at higher temperatures also affected the starch granule morphology and the pasting properties. Waxy rice changed its appearance from opaque white to translucent when being dried at 130 °C.     

Effect of drying air temperature and storage on industrial and chemical quality of rice grains

The drying air temperature and storage time can change the milling yield and chemical composition of rice grains. Therefore, the objective was to verify the industrial quality and chemical composition of rice grains, white and integral subgroups, in response to drying air temperature and storage time. For such, the rice grains were subjected to drying in a column dryer with a grain capacity of 1 m³, using 55 and 65 °C drying air temperatures. After, they were stored in PP Woven Bags under environmental conditions for 240 days. After drying and every 60 days the milling was performed, aiming to evaluate the industrial quality and chemical composition of the grains. The whole grains yield was negatively affected by the increase in drying air temperature for both subgroups. The increase in the drying air temperature led to a reduction in the lipid content and an increase in the ash content for grains of white subgroup. The storage time promoted an increase in the whole grains yield in the white subgroup when the grains were dried with the highest drying air temperature. The lipids and proteins contents decreased, while the fibers and ash contents increased during storage for the white subgroup grains. The chemical composition of grains from the brown subgroup did not change during storage, regardless of drying air temperature.     

Intermittent drying simulation in a deep bed dryer of yerba maté

In the present research, the reduction of energy consumption was evaluated during drying of yerba maté branches when tempering periods were applied. An empirical model was validated describing the moisture variation with time and process temperature, using different operation conditions. This model was used to simulate an industrial dryer in order to minimize energy consumption, maintaining the final moisture content constant. Best results were obtained working in the following conditions: application of heat for 15 min, 15 min of tempering and continuous application of heat. The bed height (1 m) was reduced in 10% maintaining the dryer production increasing the belt velocity. Working with these conditions a 10% of energy consumption can be reduced.     

Using ultrasonic vacuum spray dryer to produce highly viable dry probiotics

Ultrasonic vacuum spray dryer was used to produce a dry powder of highly viable probiotic cells. The drying was performed through two stages: Vacuum spray drying of the solution followed by fluidized-bed drying of the powder. The embedding matrix was a combination of trehalose and maltodextrin. The effects of external and internal variables on cell survival during the drying process and storage were investigated. The hypothesis was that by minimizing the oxidative and thermal stresses in the drying stages, in addition to adequate formulation choice, the cell viability during the drying and storage will increase. It was concluded that during the drying process the faster the embedding matrix reaches a glassy state the higher was the probiotic survival. Evaluating water activity and moisture limit of the glassy matrix concluded that maltodextrin DE5 is a better encapsulating matrix than maltodextrin DE19. Combining trehalose to maltodextrin in the encapsulating matrix resulted in a significant increase in the survival up to 70.6 ± 6.2%.     

Water desorption isotherm and drying characteristics of green soybean

There is very little published information on green soybean about moisture sorption and drying. Water desorption isotherms were determined by the static gravimetric method using saturated salt solutions at 20, 30, and 40 °C. By comparing the index of goodness of fit, the isotherm for green soybean seeds could be better described by the Halsey equation with the desorption isotherm parameters A and B estimated to be 5.612 and 1.538 respectively. The net isosteric heat of water desorption calculated by Clausius–Clapeyron equation was from 208.8 to 3627.9 kJ/kg. Thin layer drying of green soybean seeds in a range of 25–45 °C and relative humidity from 0.2 to 0.4 dec were carried out with a heat pump dryer. The Page model was the most suitable model for describing the thin layer drying process of green soybean seeds compared with the Lewis, Henderson and Thompson models. The drying characteristics of green soybean seeds were tested and analyzed under various temperature and humidity conditions, and the results will be useful for the drying and storage of green soybean seeds.     

我国高水分稻谷干燥工艺设备的研究设计及应用

提出了适合我国国情的高水分稻谷逆顺流多级变温组合干燥工艺方案,设计了HNST系列环保型连续式逆顺流高水分稻谷保质干燥机,阐述了其干燥原理、主要结构和性能特点。实践证明,该机型热效率高、节能显著、环保、干燥后粮食品质好、连续生产,可使粮食一次降至安全水分、自动化程度高、可操作性强、通用性及适用性好、便于系列化和标准化生产,具有广阔的市场推广前景。     

板栗干燥特性及干燥机的开发研究

干燥设备目前种类很多,但能用于板栗干燥的干燥机极少。本文针对板栗的特殊干燥特性,开发出一种新型的板栗干燥机,该机具有热利用率高,能耗少,结构简单,无需大量配套设备,可以单机使用,适用性广。目前该机已成功应用于带壳板栗的干燥。     

Improved quality and energy performance of a fixed-bed longan dryer by thermodynamic modifications

Modifications including air deflector installations in the plenum and insulation to improve performance of an industrial longan dryer were evaluated. Trials were carried out at a commercial drying facility according to industrial practices. Analyses of drying conditions, product quality and energy consumption were conducted. The study found that air velocity distribution was improved by plenum modifications and heat supply was more consistent after insulation. Modifications increased drying uniformity and insulation produced more homogenous product color. Evaluation of dryer performance showed that inverted mesh in the plenum and insulation reduced energy demand and increased efficiency by 1.51–4.27% respective of dryer modification. Cost savings of US$ 4–10 per batch were calculated with an estimated payback period of 5–12 batches. In conclusion, simple modifications of this dryer type show potential for improving product uniformity, reducing energy requirement and increasing profitability. Combination of the best modifications is recommended for further research.     

Garlic dehydration inside heat exchanger-evacuated tube assisted drying system: Thermal performance,drying kinetic and color index

An experimental investigation was done on an advanced evacuated tube-assisted solar drying system without and with load conditions at various water flow rates (10 L/h, 20 L/h, and 30 L/h) to evaluate its performance analysis. 79.56 °C maximum greenhouse air temperature was recorded without load at 30 L/h water flow rate with an average solar intensity of 850 W/m². Highest value of drying rate (DR) is 1.48 kgH₂O/kg dry solid/h and the maximum efficiency of solar collector (SC) and solar dryer (SD) is 43.62% and 55.28%, respectively, at 30 L/h water flow rate. Garlic was dehydrating from 70% to 8% (wb) moisture content (MC). The maximum exergy efficiency (EE) and minimum exergy loss were 57.64% at 30 L/h water flow rate and 4.58 W at 10 L/h water flow rate. Quality assessment is also carried out for dried garlic samples in the heat exchanger –evacuated tube assisted drying system (HE-ETADS). Color conservation (indices) of dehydrated garlic sample is best in HE-ETADS (L_o = 60.42, a_o = −0.92, and b_o = 11.54) in comparison to old-style (traditional) drying process (L_o = 58.89, a_o = - 0.67, and b_o = 5.99). Therefore, the developed drying system represented not only good financial returns but also better product quality. The present system provides interesting options for the entry of this type of collectors in medium-scale applications in the agricultural and industrial sectors.     

Effects of vacuum and microwave freeze drying on microstructure and quality of potato slices

Potato slices immersed in 0.5% CaCl₂ solution for 10 min were examined using light microscopy for their microstructure in frozen state before drying, during the sublimation drying stage, in the desorption drying stage and in the final dried form. Additionally, the final dried product was also tested for vitamin C content, color, starch content, texture and sugar content. Experiments were carried out using conventional vacuum freeze dryer as well as a microwave freeze dryer. Results for both unblanched and blanched potato tissues, crystal growth during sublimation drying stage was observed to cause structural damage to the cell walls. Blanched tissue suffered more damage during the freezing process. Interestingly, microwave freeze drying yielded product similar in quality to that obtained in vacuum freeze drying with conductive heating.     

造纸机的新型多通道烘缸

目前的造纸机烘缸大多采用虹吸管式冷凝水排出装置,由于受烘缸积水的影响,导致传统烘缸的干燥效率下降,纸页受热不均匀。基于此,介绍了对该传统结构进行改进的方法,采用多通道式冷凝排水装置,并将2种烘缸在干燥机理、传热效率和干燥设备的技术性能指标等方面进行了详细的比较,得出了多通道式烘缸干燥效率高。能耗小等优点。