Search Results (20)

Grain drying technology is a core process for ensuring food quality, extending storage life, and improving processing adaptability. With the continuous growth of global food demand and the increasing requirements for food quality and energy efficiency, traditional drying technologies face multiple challenges. This paper reviews six major grain drying technologies, comprising hot air drying, microwave drying, infrared drying, freeze drying, vacuum drying, and solar drying. It provides an in-depth discussion of the working principles, advantages, and limitations of each technology, and analyzes their performance in practical applications. In response to challenges such as high energy consumption, uneven drying, and quality loss during the drying process, the paper also explores the research progress of several hybrid drying systems, such as microwave–hot air drying combined systems and solar–infrared drying systems. Although these emerging technologies show significant potential in improving drying efficiency, energy saving, and maintaining food quality, their high costs, scalability, and process stability still limit large-scale applications. Therefore, future research should focus on reducing energy consumption, improving drying precision, and optimizing drying system integration, particularly by introducing intelligent control systems. This would maximize the preservation of food quality while improving the system’s economic efficiency and sustainability, promoting innovation in food production and processing technologies, and further advancing global food security and sustainable agricultural development. Full article

This study explores the combined use of convective and infrared drying (CIRD) for bread slices, utilizing advanced MEMS sensors to monitor temperature, moisture, and drying rates in real time, optimizing efficiency, and energy use. The dehydration kinetics of 1 cm thick bread slices under a controlled CIRD method was used. This analyzes drying rate (water loss speed, WLS) and energy efficiency (EE) using sensor technology. IR drying used 150 W lamps at 7 cm and 15 cm, while convective drying involved 60 °C hot air at 3 m/s. Sensor data aligned with gravimetric measurements. The most energy-efficient model used a 150 W IR lamp at 7 cm (0.645 kWh, 21.572 kWh/kg water removed) but had the longest drying time (220 min at 15 cm). The least efficient model used a 250 W IR lamp at 15 cm (EE = 32.734 kWh/kg). These results of CIRD in bread drying are statistically significant and can be applied to industrial bakery drying processes, helping manufacturers to reduce energy costs, and adopt sensor-driven process control for enhanced sustainability. The CIRD model, which uses a 150 W IR lamp placed 15 cm above the bread slices being dried, represents the most effective optimization strategy. Full article

This study examined the effects of hot air drying (HAD), infrared radiation drying (IRD), microwave vacuum drying (MVD), freeze drying (FD), and freeze drying combined with microwave vacuum drying (FD-MVD) on the drying kinetics, color, rehydration ratio, titratable acidity, and vitamin C content of small white apricots (Prunus armeniaca L.). Results showed drying times of 12.5 h (IRD), 14.1 h (FD), 16 h (HAD), 0.53 h (MVD), and 6.15 h (FD-MVD). FD-MVD significantly outperformed MVD, HAD, and IRD in color, vitamin C, titratable acidity, and rehydration, though was slightly inferior to FD. Microstructural analysis revealed that FD-MVD preserved the most uniform pore structure, better maintaining apricots’ original appearance. In contrast, IRD and HAD caused severe surface shriveling, compromising quality. In conclusion, FD-MVD emerges as a promising drying method to enhance apricot quality and market competitiveness in food processing. Full article

To fully leverage the advantages of both hot air drying and radio frequency vacuum drying, a segmented combination drying technique was applied to post-harvest Cistanche. This new drying method involves using hot air drying in the initial stage to remove the majority of free water, followed by radio frequency vacuum drying in the later stage to remove the remaining small amount of free water and bound water. During the radio frequency vacuum drying (RFV) phase, the effects of temperature (45, 55, and 65 °C), vacuum pressure (0.020, 0.030, and 0.040 MPa), plate spacing (65, 75, and 85 mm), and slice thickness (4, 5, and 6 mm) on the drying characteristics, quality, and microstructure of Cistanche slices were investigated. Additionally, infrared thermal imaging technology was used to examine the surface temperature distribution of the material during the drying process. The results showed that compared to radio frequency vacuum drying alone, the hot air–radio frequency combined drying significantly shortened the drying time. Under conditions of lower vacuum pressure (0.020 MPa), plate spacing (65 mm), and higher temperature (65 °C), the drying time was reduced and the drying rate increased. Infrared thermal imaging revealed that in the early stages of hot air–radio frequency vacuum combined drying, the center temperature of Cistanche was higher than the edge temperature. As drying progressed, the internal moisture of the material diffused from the inside out, resulting in higher edge temperatures compared to the center and the formation of overheating zones. Compared to natural air drying, the hot air–radio frequency vacuum combined drying effectively preserved the content of active components such as polysaccharides (275.56 mg/g), total phenols (38.62 mg/g), total flavonoids (70.35 mg/g), phenylethanoid glycosides, and iridoids. Scanning electron microscopy observed that this combined drying method reduced surface collapse and cracking of the material. This study provides theoretical references for future drying processes of Cistanche. Full article

Sea buckthorn has garnered significant attention owing to its nutritional richness; however, it has a limited shelf life. In this study, the drying process of sea buckthorn was categorized into the first-, second-, and third-drying stages. Regression models were employed to examine the effects of the drying temperature, relative humidity of the medium, and prolonged high humidity retention on various parameters during the first- and second-drying stages. Comparative analysis revealed that the optimal drying conditions for the first-drying stage of sea buckthorn were a drying temperature of 80 °C, relative humidity of 28%, and high humidity retention time of 84 min. In the second-drying phase, the optimal conditions were a drying temperature of 78 °C, a relative humidity of 17%, and a high humidity retention time of 84 min. One-way optimization revealed that the optimal drying temperature for the third-drying stage was 70 °C. The implementation of temperature- and humidity-controlled infrared hot-air drying (TH-IRHAD) techniques considerably improved the outcomes. Specifically, the drying time, energy consumption, and degree of browning decreased by 34.43%, 36.29%, and 21.43%, respectively, whereas the brightness, rehydration ratio, total flavonoid content, and total phenol content increased by 8.94%, 16.99%, 20.57%, and 28.32%, respectively. Staged TH-IRHAD substantially reduced the drying duration, increased the efficiency, and enhanced the drying quality. Full article

Drying is an important preservation method of casein. Traditional natural draining and drying processes have low efficiency, long processing time, and poor product quality, which urgently need to be improved. This study investigated the effects of pre-dehydration intensities (30 N 30 min (PreD1) and 50 N 30 min (PreD2)) and drying methods (including pulsed vacuum drying (PVD), infrared drying (IRD), and hot air drying (HAD)) on the drying kinetics, drying modeling, and quality of yak milk casein. These findings reveal that PreD2 and PVD both had a positive impact on shortening the drying time. Compared to other combined treatments, PreD2-PVD had the shortest drying time of 6 h. The Midilli–Kucuk mathematical model effectively predicted the drying of casein. The yak milk casein powder treated with PreD2-PVD possessed a higher content of gross compositions, superior color, lower levels of fat oxidation and 5-hydroxymethylfurfural (5-HMF), and higher emulsifying activity index (EAI) and emulsion stability index (ESI) values. Overall, combining pre-dehydration with PVD proved effective in improving the drying rate and maintaining a good quality of yak milk casein, showing promising potential for industrial applications. Full article

In this paper, the effects on drying time (Y₁), the color difference (Y₂), unit energy consumption (Y₃), polysaccharide content (Y₄), rehydration ratio (Y₅), and allantoin content (Y₆) of yam slices were investigated under different drying temperatures (50–70 °C), slice thicknesses (2–10 mm), and radiation distances (80–160 mm). The optimal drying conditions were determined by applying the BP neural network wolf algorithm (GWO) model based on response surface methodology (RMS). All the above indices were significantly affected by drying conditions (p < 0.05). The drying rate and effective water diffusion coefficient of yam slices accelerated with increasing temperature and decreasing slice thickness and radiation distance. The selection of lower temperature and slice thickness helped reduce the energy consumption and color difference. The polysaccharide content increased and then decreased with drying temperature, slice thickness, and radiation distance, and it was highest at 60 °C, 6 mm, and 120 mm. At 60 °C, lower slice thickness and radiation distance favored the retention of allantoin content. Under the given constraints (minimization of drying time, unit energy consumption, color difference, and maximization of rehydration ratio, polysaccharide content, and allantoin content), BP-GWO was found to have higher coefficients of determination (R² = 0.9919 to 0.9983) and lower RMSEs (reduced by 61.34% to 80.03%) than RMS. Multi-objective optimization of BP-GWO was carried out to obtain the optimal drying conditions, as follows: temperature 63.57 °C, slice thickness 4.27 mm, radiation distance 91.39 mm, corresponding to the optimal indices, as follows: Y₁ = 133.71 min, Y₂ = 7.26, Y₃ = 8.54 kJ·h·kg⁻¹, Y₄ = 20.73 mg/g, Y₅ = 2.84 kg/kg, and Y₆ = 3.69 μg/g. In the experimental verification of the prediction results, the relative error between the actual and predicted values was less than 5%, proving the model’s reliability for other materials in the drying technology process research to provide a reference. Full article

The objective of this research was to investigate the effect of infrared-combined hot air intermittent drying (IIRHAD) on energy consumption, drying characteristics, and the quality of jujube slices. The water content of jujube slices decreased from 0.267 g/g to 0.05 g/g during the experiment, and the infrared heating plate’s temperature was fixed at 70 °C while the hot air temperature was fixed at 50 °C. Nine different intermittent ratios were used to dry jujube slices, and the results showed that intermittent treatment had varying effects on drying characteristics, energy consumption, and quality. In comparison to infrared-combined hot air drying (IRHAD), the effective drying time of red jujube slices was reduced by 40 to 100 min, the energy consumption decreased by 11.91% to 34.34%, and there were also varying degrees of improvement in the quality indicators. It was discovered that excessively long or short active drying and tempering periods had a negative impact on the drying process. Therefore, these factors should be further broken down and improved in the future. This research holds great importance for the future advancement and widespread use of IIRHAD in fruit and vegetable materials. Full article

This present study investigated thin-layer drying characteristics of dried apple slices for a range of temperatures from 40 °C to 80 °C at a constant drying time of 10 h under infrared (IR) and hot air oven (OV) drying methods. The fresh apples were cut into a cylindrical size of thickness of 8.07 ± 0.05 mm and a diameter of 66.27 ± 3.13 mm. Fourteen thin-layer mathematical models available in the literature were used to predict the drying process. The goodness of fit of the drying models was assessed by the root mean square error (RMSE), chi-square (χ²), coefficient of determination (R²) and modelling efficiency (EF). The results showed that the lightness and greenness/redness of the dried sample, total colour change, chroma change, colour index, whiteness index, bulk density, final surface area and final volume significantly (p-value < 0.05) correlated with the drying temperature under IR. Under OV, however, only the final surface area and bulk density of the dried samples showed significant (p-value < 0.05) with the drying temperature. Shrinkage values for OV and IR methods showed both increasing and decreasing trends along with the drying temperatures. The Weibull distribution model proved most suitable for describing the drying processes based on the statistical validation metrics of the goodness of fit. In future studies, the combined effect of the above-mentioned drying methods and other drying techniques on apple slices among other agricultural products should be examined to obtain a better insight into the drying operations and quality improvement of the final product for preservation and consumer acceptability. Full article

Using hot air drying (HAD) and combined infrared hot air drying (IR-HAD) test devices, the drying kinetics, unit energy consumption, color difference values, rehydration rate, microstructure, and changes in polysaccharide and allantoin contents of yam slices were examined at various temperatures (50 °C, 55 °C, 60 °C, 65 °C, and 70 °C). The findings demonstrated that each of the aforementioned parameters was significantly impacted by the drying temperature. IR-HAD dries quicker and takes less time to dry than HAD. The D_eff of IR-HAD is higher than that of HAD at the same temperature and increases with the increase in temperature. The activation energy required for IR-HAD (26.35 kJ/mol) is lower than that required for HAD (32.53 kJ/mol). HAD uses more energy per unit than IR-HAD by a factor of greater than 1.3. Yam slices treated with IR-HAD had higher microscopic porosity, better rehydration, lower color difference values, and higher polysaccharide and allantoin levels than HAD-treated yam slices. The IR-HAD at 60 °C had the greatest comprehensive rating after a thorough analysis of the dried yam slices using the coefficient of variation method. Three statistical indicators were used to evaluate six thin-layer drying models, and the Weibull model was most applicable to describe the variation of drying characteristics of yam slices. Full article

The drying process is one of the oldest methods used to obtain food products that could be stored for a long time. However, drying is an energy-intensive process. Additionally, convective drying, due to the high temperature used during the process, results in loss in bioactive substances as well as nutritional value. Thus, in this research, apple slices were dried in a combined hot air–infrared air dryer with four different drying strategies and drying kinetics, internal and external mass transfer (Crank and Dincer models), and then the energy parameters were investigated. The first, second, third, and fourth strategies, respectively, include one-stage drying with a hot air (HA) or infrared energy source (IR), one stage but with two sources of hot air and infrared (HA–IR), and then there are two stages of first hot air and then infrared drying (HA+IR) and vice versa (IR+HA). According to the results, the highest effective moisture diffusion coefficient of the two Crank and Dincer models was equal to 1.49 × 10⁻⁹ and 1.55 × 10⁻⁸ m²/s, obtained in the HA70–IR750, and the lowest effective moisture diffusion coefficient was equal to 1.8 × 10⁻¹⁰ and 2.54 × 10⁻⁹ m²/s, obtained in IR250+HA40. The maximum (10.25%) and minimum (3.61%) energy efficiency were in the IR750 and HA55–IR250 methods, respectively. Moreover, the highest drying efficiency (12.71%) and the lowest drying efficiency (4.19%) were obtained in HA70+IR500 and HA40–IR250, respectively. The value of specific energy consumption was 15.42–51.03 (kWh/kg), the diffusion activation energy was 18.43–35.43 (kJ/mol), and the value of the specific moisture extraction rate (SMER) was in the range of 0.019–0.054 (kWh/kg). Compared to the other strategies, the second strategy (HA–IR) was better in terms of drying time and mass transfer, and the third strategy (HA+IR) was more efficient in terms of energy efficiency and drying efficiency. The infrared drying in the first strategy was better than that in the other methods in the other strategies in terms of retention of bioactive compounds. Full article

A drying device based on infrared radiation heating technology combined with temperature and humidity process control technology was created to increase the drying effectiveness and quality of sea buckthorn. Based on the conventional k-turbulence model, the velocity field in the air distribution chamber was simulated using COMSOL 6.0 software. The airflow of the drying medium in the air distribution chamber was investigated, and the accuracy of the model was verified. Given that the inlet of each drying layer in the original model had a different velocity, the velocity flow field was improved by including a semi-cylindrical spoiler. The results showed that installation of the spoiler improved the homogeneity of the flow field for various air intakes, as the highest velocity deviation ratio dropped from 26.68% to 0.88%. We found that sea buckthorn dried more rapidly after being humidified, reducing the drying time by 7.18% and increasing the effective diffusion coefficient from 1.12 × 10⁻⁸ to 1.23 × 10⁻⁸ m²/s. The L*, rehydration ratio, and vitamin C retention rate were greater after drying with humidification. By presenting this hot-air drying model as a potential high-efficiency and high-quality preservation technology for sea buckthorn, we hope to advance the development of research in the sea buckthorn drying sector. Full article

Large amounts of waste result from licorice mold rot; moreover, prompt drying directly influences product quality and value. This study compared various glycyrrhiza drying methods (Hot air drying (HAD), infrared combined hot air drying (IR-HAD), vacuum freeze drying (VFD), microwave vacuum drying (MVD), and vacuum pulsation drying (VPD)) that are used in the processing of traditional Chinese medicine. To investigate the effects of various drying methods on the drying characteristics and internal quality of licorice slices, their color, browning, total phenol, total flavonoid, and active components (liquiritin and glycyrrhizic acid) were chosen as qualitative and quantitative evaluation indices. Our results revealed that VFD had the longest drying time, but it could effectively maintain the contents of total phenol, total flavonoid, and liquiritin and glycyrrhizic acid. The results also showed that VFD samples had the best color and the lowest degree of browning, followed by HAD, IR-HAD, and VPD. We think that VFD is the best approach to ensure that licorice is dry. Full article

The boreal hemisphere has been experiencing increasing extreme hot and dry conditions over the past few decades, consistent with anthropogenic climate change. The continental extension of this phenomenon calls for tools and techniques capable of monitoring the global to regional scales. In this context, satellite data can satisfy the need for global coverage. The main objective we have addressed in the present paper is the capability of infrared satellite observations to monitor the vegetation stress due to increasing drought and heatwaves in summer. We have designed and implemented a new water deficit index (wdi) that exploits satellite observations in the infrared to retrieve humidity, air temperature, and surface temperature simultaneously. These three parameters are combined to provide the water deficit index. The index has been developed based on the Infrared Atmospheric Sounder Interferometer or IASI, which covers the infrared spectral range 645 to 2760 cm⁻¹ with a sampling of 0.25 cm⁻¹. The index has been used to study the 2017 heatwave, which hit continental Europe from May to October. In particular, we have examined southern Italy, where Mediterranean forests suffer from climate change. We have computed the index’s time series and show that it can be used to indicate the atmospheric background conditions associated with meteorological drought. We have also found a good agreement with soil moisture, which suggests that the persistence of an anomalously high water deficit index was an essential driver of the rapid development and evolution of the exceptionally severe 2017 droughts. Full article

Chrysanthemum (Chrysanthemum morifolium Ramat.) is a seasonal plant with high medicinal and aesthetic value, and drying is an effective practice to enhance its storability after harvesting. The effects of hot air drying (HAD), combined infrared and hot air drying (IR-HAD), and sequential IR-HAD and HAD (IR-HAD + HAD) on the drying behavior, color, shrinkage, aroma profiles, phenolic compounds, and microstructure of chrysanthemum cakes were studied. Results showed that the increasing temperature resulted in a decrease in drying time and an increase in drying rate and moisture diffusivity. The Logarithmic and Page models exhibited superior fit in describing the dehydration process. Among the three drying strategies, IR-HAD was more effective in reducing energy consumption, improving shrinkage, water holding capacity, water binding capacity and cellular microstructure, while IR-HAD + HAD showed better inhibitory effect on color deterioration. Furthermore, gas chromatography–mass spectrometry (GC-MS) analysis revealed that different drying strategies dramatically influenced the aroma profiles in samples, and IR-HAD obtained the highest concentration of volatiles. The results of ultra-performance liquid chromatography (UPLC) indicated that the introduction of infrared radiation contributed to increasing the contents of chlorogenic acid, luteolin, total phenolic and flavonoid. These suggested that IR-HAD was a promising technique for drying medicinal chrysanthemum. Full article