Comparison of Drying Characteristics and Quality of Shiitake Mushrooms (Lentinus edodes) Using Different Drying Methods

The objective of this study was to compare the drying characteristics and the quality of dried Shiitake mushroom (Lentinus edodes) cubes obtained by hot-air drying (HAD), intermediate-infrared drying (IIRD), and vacuum microwave spouted-bed drying (VMSD). Several quality parameters of products, including color, texture, and rehydration capacity, were investigated. Compared to IIRD and VMSD, HAD turn out to be the most undesirable method due to its longer drying time and poor product quality. With similar rehydration capacity, the color of the VMSD product was closest to the original material. In terms of texture, total sugar content, and sensory evaluation, the VMSD product has the best quality.     

Drying of shiitake mushroom by combining freeze-drying and mid-infrared radiation

Mid-infrared drying (MIRD) was applied before or after freeze-drying (FD) of shiitake mushroom to shorten the drying time, to enhance the rehydration, and to better preserve the aroma compounds and color. The effect of application of MIRD before freeze drying (MIRD–FD) and after freeze drying (FD–MIRD) on drying time, color, rehydration ratio, apparent density, microstructure and aroma compounds was measured, explained and compared with the effect of FD on these parameters. The results showed that the combination of FD (for 4 h) followed by MIRD saves 48% time compared to FD while keeping the product quality at an acceptable level. The MIRD–FD combination was found to be inferior compared to the FD–MIRD as the former tended to produce products with a collapsed surface layer and poor rehydration capability. The combination of MIRD with FD had a significant effect on aroma retention and caused an increase of sulfur compounds such as dimethyl, trisulfide and 1,2,4-trithiolane.     

Evaluation of Thin-Layer Models for Mushroom (Agaricus bisporus) Drying

In the present research, seven well-known mathematical thin-layer drying models were fitted to mushroom (Agaricus bisporus) drying experimental data, implementing nonlinear regression analysis techniques. The experiments were conducted in two laboratory-scale dryers. A range of temperatures 50–65°C and air velocities 1.0–5.0 m/s were tested. The statistical analysis concluded that the best model in terms of fitting performance was the logarithmic model. Correlations expressing this model parameter dependence with the drying air coefficients are also reported.     

Evaluation of Thin-Layer Models for Mushroom (Agaricus bisporus) Drying

In the present research, seven well-known mathematical thin-layer drying models were fitted to mushroom (Agaricus bisporus) drying experimental data, implementing nonlinear regression analysis techniques. The experiments were conducted in two laboratory-scale dryers. A range of temperatures 50-65°C and air velocities 1.0-5.0 m/s were tested. The statistical analysis concluded that the best model in terms of fitting performance was the logarithmic model. Correlations expressing this model parameter dependence with the drying air coefficients are also reported.     

Drying and Quality Characteristics of Shredded Squid in an Infrared-Assisted Convective Dryer

Drying is one of the most common methods for processing and preserving squids. A novel forced convective dryer based on infrared heating was developed with an online temperature control. By setting the drying medium temperature of 50°C, we studied the effects of infrared wavelength and air velocity on drying characteristics of the shredded squid and qualities of dried squid products. We also compared it with the conventional hot-air drying (HAD) and advanced microwave vacuum drying (MVD). The infrared heating rate increase was faster than that of HAD. The heating and drying at the wavelength of 2.5–3.0 µm were more effective than those at the infrared wavelength of 5.0–6.0 µm. Specific energy consumption linearly increased with the air velocity. Microstructure observation showed that the infrared-dried rehydrated sample displayed a muscle fiber structure similar to the fresh sample. The infrared-dried squids had less drying shrinkage, brighter color, and better rehydration capacity than HAD products. Their sensory qualities were better than HAD and MVD products. Above all, infrared drying with wavelength of 2.5–3.0 µm and air velocity of 0.5 m/s was suggested as the best drying condition for squids in this study.     

Effects of Salting and Drying on Shark (Carcharhinus sorrah) Meat Quality Characteristics

The effect of drying method and pretreatment with salt on the properties of shark meat was investigated. Water loss during the salting step was faster with dry salting than with brine salting; however, both methods led to the same final water content at the end of the drying process. Moisture desorption isotherms showed that addition of salt prior to sun or air drying resulted in lower equilibrium moisture contents at the same water activity levels. Salting and method of drying had significant effects on the microbial load. Osmo-air-dried samples showed better microbial quality than samples treated by other methods. Molds grew on all samples after two months of storage at room temperature. Color and rehydration ratio were affected by the drying method. Higher dehydration ratios were obtained with air drying.     

Effect of Drying Methods on the Quality Characteristics of Fenugreek (Trigonella foenum-graecum) Greens

Different drying methods were investigated for efficient dehydration of fenugreek (Trigonella foenum-graecum) greens for optimal retention of color and its constituents. Accordingly, hot air (HA, 40°C, 58–63% RH), low humidity air (LHA, 40°C and 28–30% RH), and radiofrequency (RF, 40°C, 56–60% RH) were explored for efficient drying of fenugreek greens. The three single-layer drying models (Exponential, Page, and Modified Page) tested showed excellent fit (R² = 0.92–0.99) for all three drying methods. The time required for drying with LHA and RF was less (～27%), as compared to HA drying. LHA-dried fenugreek had superior green color and a more porous and uniform structure than those obtained from RF and HA drying. Aqueous methanolic (60:40) extract of fenugreek greens dehydrated by LHA exhibited the highest radical scavenging activity. Dehydrated fenugreek greens showed good consumer acceptance as well as shelf life.     

Drying Characteristics of Textured Soy Protein: A Comparison between Three Different Products

The drying curves of three commercial types of textured soy protein were determined in a pilot air dryer operated at three different temperatures (90, 110, and 130°C), three different drying air velocities (1.00, 1.25, and 1.50 m/s), and different heights of product layer. Drying air temperature influenced significantly all the drying curves; the height of product layer influenced only the drying of TSP types I and II. The effect of drying air velocity was found to be the lowest. A mathematical model was used in the development of a model capable of predicting the drying curves of these products.     

Drying of Mushroom Slices Using Hot Air Combined with an Electrohydrodynamic (EHD) Drying System

In this study, hot air combined with EHD drying is examined as an improved method for drying mushroom slices. The effects of three levels of voltage (17, 19, and 21 kV) and electrode gap (5, 6, and 7 cm) on the drying kinetics, time, effective water diffusion coefficient, and energy consumption of the EHD, pure hot air (provided within a chamber), and hot air combined with EHD drying systems were investigated. ANOVA showed that there were significant differences between EHD treatments and control (pure hot-air-drying treatment) for all of the investigated responses. Voltage and electrode gap factors had significant effects on all investigated responses. The results confirmed that the combination of EHD and hot air can significantly reduce the drying period, resulting in a greater effective water diffusion coefficient and drying rate and reduced energy consumption. As such, this technique offers a promising solution to the considerable energy consumption of the drying industry.     

Drying Characteristics of Textured Soy Protein: A Comparison between Three Different Products

The drying curves of three commercial types of textured soy protein were determined in a pilot air dryer operated at three different temperatures (90, 110, and 130°C), three different drying air velocities (1.00, 1.25, and 1.50 m/s), and different heights of product layer. Drying air temperature influenced significantly all the drying curves; the height of product layer influenced only the drying of TSP types I and II. The effect of drying air velocity was found to be the lowest. A mathematical model was used in the development of a model capable of predicting the drying curves of these products.     

Comparative Analysis of Three Methods for Stochastic Lumber Drying Simulation

Abstract:

This article describes a novel stochastic model designed to simulate systems that cannot be analyzed as a unit, but as a collection of a large number of similar components. In order to state advantages and disadvantages, the proposed method is compared with two other published models. The first is a symbolic mathematical relationship designed to predict average moisture content and standard deviation after conventional drying of lumber. Since this model is exact, it was used as reference to evaluate the accuracy of the other approximate numerical methods. The second model is entirely random, and it emulates a real system behavior in which the parameters and conditions randomly change from one component to the other. The proposed method is based on numerical integration of the parameter's frequency distribution curves, which always produce the same and most probable result for the same parameters and conditions. The three methods were applied for simulation of conventional lumber drying, and the results were compared both qualitatively and numerically.     

Combined Infrared-Convective Drying of Murta (Ugni molinae Turcz) Berries: Kinetic Modeling and Quality Assessment

Murta (Ugni molinae Turcz) berries were dried under convective and combined convective-infrared conditions at 40, 50 and 60°C and 400–800 W in order to determine the drying characteristics and to compare the dried product's quality. To model the drying kinetics, seven mathematical equations were fitted to experimental data. According to statistical tests performed, the Midilli-Kuçuk model best fitted experimental data and was closely followed by the logarithmic model. Effective moisture diffusivity also showed dependency on drying conditions and varied between 7.59 × 10^?10 to 44.18 × 10^?10 m²/s and 11.34 × 10^?10 to 85.41 × 10^?10 m²/s for air-convective drying and combined infrared-convective drying. As to quality attributes of the berries, total surface color difference (ΔE) and total phenolic content (TPC) were determined. It was found that chromaticity coefficients a* and b* changed significantly, showing ΔE to be dependent on the mode of heat supply. TPC under all drying conditions decreased and was significantly different from the initial value in fresh samples. However, at a constant drying temperature, an increase in infrared power enhanced retention of TPC in samples. In particular, working at 40°C/800 W resulted in dried samples with the highest TPC.     

Kinetic and Quality Study of Mushroom Drying under Microwave and Vacuum

Abstract

The aim of this work is to model the drying kinetics of mushrooms under several operational conditions, to evaluate the effective diffusivity coefficient of moisture removing by a drying model and inverse calculus method in finite differences and to study the effect on the final quality of dehydrated mushrooms. Different ways of microwave vacuum drying were compared to freeze-drying. Results show that a decrement of the applied pressure produces a certain increase in the drying rate together with a lower moisture in the dehydrated product at the end. Temperature control inside the sample helps to ensure a better quality in the dehydrated product, than when controlled at the surface. Diffusivity coefficients show a correspondence with product temperature during drying. The microwave dried samples obtained with moderate power and temperature control of product shown an important degree of quality similar to that obtained by freeze-drying.     

Dewatering and Drying Methods for Microalgae

Microalgae can efficiently fix carbon dioxide through their phototropic metabolism, and have been recognized as a promising bioresource for animal feed, health food, fuel, cosmetic, and pharmaceutical products. However, since microalgae in cultivated medium have a low biomass concentration (0.1–1% w/w), both harvesting and concentration of microalgal biomass are often required prior to the production of commercial products. Efficient and cost-effective dewatering and drying methods for microalgae heavily affect the overall energy consumption and production cost of microalgal products. This review describes the characteristics of commonly used dewatering and drying technologies, and critically evaluates the feasibility for their use to treat microalgal biomass. No single dewatering or drying method can satisfactorily handle all types of microalgae. The suitability of each method depends on the properties of the microalgae suspension, the required process design, the quality of the end product, and the related capital and production costs.     

Quality of Soybean Seeds Undergoing Moving Bed Drying: Countercurrent and Crosscurrent Flows

The present work describes and analyzes Brazilian research related to the quality of soybean seeds dried in moving bed dryers. The main process variables were drying air temperature, relative humidity and velocity, and solid flow rate. The statistical methodology used allowed the achievement of empirical equations for predicting the quality of soybean seeds (germination, vigor, and fissures) in two classical configurations of the moving bed: countercurrent and crosscurrent. The results show that the increase of the seed coat cracking is associated to conditions that lead to a high drying rate. Germination and vigor reduction is also associated to the overdrying conditions.     

Use of Ultrasound Pretreatment in Drying of Fruits: Drying Rates,Quality Attributes,and Shelf Life Extension

Evolving advanced pretreatment techniques such as application of ultrasound prior to fruit drying have attracted significant research and development efforts due to the rising demand for high-quality dried fruits at reduced operating costs. Drying processes can be destructive to the quality of fruits due to long drying times and high temperatures in some cases. The effects of ultrasound pretreatment on quality aspects of dried fruits and on drying kinetics are reviewed. Ultrasound is known for its varying effects on different fruits; however, it has been proved to greatly increase drying rates and hence reduce the overall processing time. Ultrasound pretreatment in distilled water as the media is an interesting concept when low-calorie dried fruits are required.     

草菇,菠萝的冷冻干燥过程及影响因素分析

从草菇、菠萝做冷冻干燥试验所得的冻干曲线和冻干时间,用分子运动论的观点分析了温度、压力等因素对冷干燥过程的影响。     

丹参叶保质干燥工艺的研究

针对丹参叶进行保质干燥,通过单因素和正交试验研究了干燥温度、风速和物料层厚度对丹参叶中丹酚酸B含量的影响。研究表明,通过单因素确定较优的干燥参数为：干燥温度50℃,风速0．6m／s,物料厚度为2层;在单因素实验基础上,通过正交实验确定的最佳保质干燥工艺参数为：A3B2C1,即干燥温度为60℃、干燥风速为0．6m／s、物料厚度为1层。     

Effect of Water on the Quality of Dehydrated Products: A Review of Novel Characterization Methods and Hybrid Drying Technologies

The effect of water on the quality of dried products is reviewed in light of recent applications of novel characterization methods (nuclear magnetic resonance (NMR), X-ray spectroscopy, and Raman spectroscopy) in quantifying the state and mobility of water in dried products. The mechanical configuration and ability of a number of hybrid drying technologies that use novel heating sources (microwave, infrared, radiofrequency) and/or sub-atmospheric pressure in producing better-quality products are reviewed in considerable detail. The drying kinetics models, especially those related to the quality loss, are also reviewed. It appears that more and more drying research is now focused on the development of novel hybrid technologies to produce better-quality products and for energy savings. The novel characterization technologies listed above are capable of quantifying the dynamic mobility and state of water in dried food products; this information can be used to design more efficient drying processes.     

A Comparative Study of Four Drying Methods on Drying Time and Quality Characteristics of Stem Lettuce Slices (Lactuca sativa L.)

This article presents experimental results and analysis of four drying methods, viz. hot air drying (AD), hot air-assisted radio frequency drying (ARFD), infrared drying (IRD), and microwave-assisted hot air drying (MAD), on color, microstructure, density, rehydration capacity, and texture after rehydration of stem lettuce slices (Lactuca sativa L.). The drying time required for these drying protocols was also compared. These four drying tests were conducted at fixed air temperature (60°C) and velocity (1 m/s), as well as identical sample load (300 g), bed depth (20 mm), and the power level for ARFD, IRD, and MAD, which was fixed at 4 W/g. The results showed that the drying time required for stem lettuce slices using ARFD was the shortest (120 min), followed by MAD (140 min) and IRD (180 min); AD required the longest time (360 min). Notably, ARFD yielded uniform drying and the quality of the dried samples using ARFD was also the best among these four drying methods.