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To clarify the effects of far-infrared drying technology on the drying kinetics and quality of broccoli rhizomes, broccoli rhizomes were dehydrated at 60, 65, 70, 75 and 80 °C, respectively. Eight thin-layer drying mathematical models were used to explore the drying kinetic characteristics and comprehensively evaluate their quality. The results showed that the higher the drying temperature, the shorter the time required to dry the broccoli rhizomes to the endpoint, and the higher the drying rate. The drying temperature was 80 °C, the shortest drying time was 360 min, and the average drying rate was 4.72 g·g−1·min−1. The longest drying time at 60 °C was 660 min, and the minimum average drying rate was 1.99 g·g−1·min−1. The effective diffusion coefficients of moisture at different drying temperatures were 1.22 × 10−6, 1.25 × 10−6, 1.34 × 10−6, 1.46 × 10−6 and 1.55 × 10−6 m2/min, respectively. The activation energy was calculated to be 12.26 kJ/mol by the linear relationship between the effective moisture diffusion coefficient and time. From the thermodynamic parameters, the drying of broccoli rhizomes is a non-spontaneous process, and it is necessary to absorb heat from the medium to achieve dehydration. With an increase in the drying temperature, the drying effect is better. The fitting results of eight mathematical models showed that Modified Page, Page, and Wang and Singh were the best mathematical models for the far-infrared drying kinetics of the broccoli rhizomes. The membership function method comprehensively evaluated the quality of the broccoli rhizome dry products. The comprehensive order was 60 °C > 65 °C > 75 °C > 70 °C > 80 °C. When the temperature was 60 °C, the physicochemical properties and nutritional quality of broccoli rhizome were well preserved, and the quality was the best. Therefore, 60 °C is the best temperature for broccoli rhizome drying. The results provide a theoretical reference for further improving the far-infrared drying quality of broccoli rhizomes. [ABSTRACT FROM AUTHOR]

Graphene exhibits exceptional electrothermal conversion efficiency, making it a promising candidate as a novel heat source for far-infrared drying. This study examined the impacts of infrared radiation temperature (45–55 °C), air flow (300–460 m3/h), and grain flow rate (6–8 kg/min) on the stress cracking index (SCI), specific energy consumption (SEC), and thermal efficiency. The Box–Behnken response surface methodology and expectation function method were employed to model and optimize the quality of far-infrared drying of paddy graphene. The findings indicate that both the drying rate and SCI of paddy increased with an increase in the infrared temperature and grain-flow rate; higher values of these parameters resulted in improved thermodynamic properties. Conversely, the SEC decreased with an increase in the infrared temperature and grain flow, whereas the thermal efficiency exhibited an inverse relationship. The influence of airflow on dried samples was negligible. Under specified constraints, the optimized drying parameters to yield a maximum expected factor were an infrared radiation air temperature of 51 °C, air flow of 377.690 m3/h, and grain flow rate of 8 kg/min. With this optimized combination of drying-process parameters, the minimum SCI reached approximately 35.4, and the minimum SEC was approximately 3734.9 kJ/kg, resulting in a maximum thermal efficiency of approximately 62.7 %. These results provide a foundation for the future development of graphene-based far-infrared grain-drying equipment.

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: Reducing the degradation of anthocyanins in blueberry during drying. Methods: The far infrared drying was applied to the drying of blueberries, and compared with traditional hot air drying to explore the degradation characteristics of major anthocyanins and the changes of PPO enzyme activity and antioxidant capacity of blueberries under different drying methods. Results: High retention of two major anthocyanins （D3G and C3G） in blueberries under far-infrared drying, and the second-order mathematical model could better simulate their degradation process. Compared with hot-air drying, the rate constants （k） and entropy values （ΔS） of far-infrared dried blueberry anthocyanins were smaller, and the half-life values （t1/2）, activation energy values （Ea） and enthalpy values （ΔH） were larger. The two drying methods produced similar effects on PPO enzyme activity, but the enzyme activity of the far-infrared drying group was generally lower than that of the hot-air drying group after 4 h. In addition, the highest anthocyanin retention and free radical scavenging ability of dried blueberry fruits were observed under far-infrared 60 ℃ drying conditions. Conclusion: Under the same drying temperature, far-infrared drying can reduce the degradation of anthocyanins and improve the drying quality of blueberries compared with traditional hot air drying.

In this paper, the effects of different ultrasonic pretreatment processes on the far-infrared drying characteristics, quality indexes, and microstructure of licorice are evaluated. The results showed that ultrasonic pretreatment, combined with far-infrared drying, significantly reduced the drying time and moisture content of licorice compared with those of the control group. The highest total flavonoid content was obtained at an ultrasound power of 80 W. The total phenolic content (0.686 mg gallic acid equivalent/g) was higher than that in the control group, the increase was 19.4%, and its content was the highest at the sonication frequency of 20 kHz. The antioxidant capacity tended to increase and then decrease with the increase in sonication time, sonication power, and sonication frequency, and was the highest at 30 min of sonication. The soluble sugar content (31.490 mg glucose equivalent/g) was the highest at 30 kHz and 30 min. Observation of the microstructure revealed that the surface structure of the ultrasonic pretreated licorice slices changed significantly, forming more micropore channels, which facilitated the mass heat transfer during the drying process. In conclusion, ultrasonic pretreatment can significantly improve the quality of licorice tablets and significantly reduce the time required for subsequent drying. The combination of pretreatment parameters of 60 W ultrasonic power and 40 kHz ultrasonic frequency for 30 min was found to be an optimal combination of pretreatment parameters; therefore, this study may provide a technical reference for the industrialization of licorice drying. [ABSTRACT FROM AUTHOR]

Copyright of Food & Machinery is the property of Food & Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mangoes have a short shelf life because of their high-water content. This study aimed to compare the effect of three drying methods (HAD, FIRD and VFD) on mango slices to improve product quality and reduce costs. Mangoes were dried at various temperatures (50, 60, 70 °C) with different slice thicknesses (3, 5, 7, 10 mm). Results indicated that FIRD was the most cost-effective with the dried mango containing the highest sugar-acid ratio, and when the mango slices thickness was 7 mm and drying at 70 °C, the ascorbic acid content, rehydration ratio, sugar-acid ratio, and energy consumption per unit volume reached 56.84 ± 2.38 mg/100 g, 2.41 ± 0.05, 83.87 ± 2.14, and 0.53 kWh/L. Among three mathematical models, the Page model described the most satisfactory drying behaviour of mango slices in FIRD. This study provides useful information in mango processing industry and FIRD is supposed to be a promising drying method.

Graphene has a high electric heating conversion rate and can be used as a new heat source for far-infrared drying equipment to improve drying efficiency and reduce energy consumption. This study aims to investigate the drying kinetics of graphene far-infrared paddy drying equipment The infrared (IR) temperatures of 35, 40, 45, 50, 55, and 60 °C; distances between radiations of 25, 30, 35, and 40 mm; grain flow of 5.0, 6.0, 7.0, 8.0, and 9.0 kg/min; and dehumidifying air velocities of 4, 5.5, 7, and 8.5 m/s were studied for appropriate drying time and optimal paddy quality. Simultaneously, the drying kinetics, moisture diffusion coefficient, and activation energy were observed. Experimental results show that the coupling degree of Midilli was superior, specifically, the Deff of paddy was 4.83–16.371 × 10−9 m2/s, an activation energy of 47.44 kJ mol−1 and a heat efficiency of 71.11% were achieved at a drying temperature of 60 °C. The far infrared drying of graphene has high moisture diffusion coefficient and thermal efficiency. By analyzing the kinetics and energy of drying process, a basis for formulating drying strategies could be provided to realize the research and development of new drying machinery.

In this study, an intelligent far-infrared drying system was developed whose output power could be adjusted in-line by computer vision and fuzzy logic controller. Ginger slices were first dried at four constant temperatures of 50 °C, 60 °C, 70 °C, and 80 °C. The images of ginger slices were captured through the top camera during the drying process. By extracting and analyzing the image features, two fuzzy logic control strategies assisted with computer vision were developed that could suppress color changes and improve product quality, including one-stage and three-stage control. The ΔE (color difference) and BI/BI0 (browning index of drying samples/browning index of fresh samples) signals as the input parameters were fed into the fuzzy logic controller for automatic adjustment of the output temperature. The results of the far-infrared drying with constant temperatures for ginger slices showed that the 60 °C drying was the best choice among the four constant temperatures. However, the ΔE and BI/BI0 of the ginger slices dried with the three-stage fuzzy logic control were lower than those of the 60 °C drying, resulting in a higher sensory score among them. In addition, the rehydration rate, water activity and total gingerol content of ginger slices dried with the three-stage fuzzy logic control suggested well accepted quality. Therefore, the stepwise fuzzy logic control can be employed for automatic in-line control to optimize the far-infrared drying process. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the effects of different ultrasonic pretreatment processes on the far-infrared drying characteristics, quality indexes, and microstructure of licorice are evaluated. The results showed that ultrasonic pretreatment, combined with far-infrared drying, significantly reduced the drying time and moisture content of licorice compared with those of the control group. The highest total flavonoid content was obtained at an ultrasound power of 80 W. The total phenolic content (0.686 mg gallic acid equivalent/g) was higher than that in the control group, the increase was 19.4%, and its content was the highest at the sonication frequency of 20 kHz. The antioxidant capacity tended to increase and then decrease with the increase in sonication time, sonication power, and sonication frequency, and was the highest at 30 min of sonication. The soluble sugar content (31.490 mg glucose equivalent/g) was the highest at 30 kHz and 30 min. Observation of the microstructure revealed that the surface structure of the ultrasonic pretreated licorice slices changed significantly, forming more micropore channels, which facilitated the mass heat transfer during the drying process. In conclusion, ultrasonic pretreatment can significantly improve the quality of licorice tablets and significantly reduce the time required for subsequent drying. The combination of pretreatment parameters of 60 W ultrasonic power and 40 kHz ultrasonic frequency for 30 min was found to be an optimal combination of pretreatment parameters; therefore, this study may provide a technical reference for the industrialization of licorice drying.

BACKGROUND Barley grass (BG) powder has gradually attracted researchers' attention for its abundant nutritional components and functional activity. Yet, the effect of different drying methods on storage stability is still unclear. In this study, BG was subjected to hot‐air drying (HAD), steam blanching prior to hot‐air drying (SHAD), vacuum freeze drying (VFD), and far‐infrared drying (FID). Effects of different drying methods on BG powder during storage were evaluated. RESULTS: Moisture content of dried samples during storage decreased at 50 °C, but at 37 °C increased first and then remained stable. The a* value of SHAD BG powder before storage was the highest (−6.51), followed by FID, HAD and VFD. Moreover, the a* value increased during the storage process. Contents of l‐ascorbic acid and total chlorophyll in samples dried by VFD were 28.29 and 7.8 g kg−1, respectively. The degradation of chlorophyll a and b followed a first‐order kinetics model and was modeled by the Arrhenius equation. The activation energies for chlorophyll a were 83.68, 83.21, 62.29 and 76.64 kJ mol−1 in BG powder dried by SHAD, FID, VFD and HAD, respectively. The activation energies for chlorophyll b were 66.76, 48.03, 61.02 and 58.01 kJ mol−1 in SHAD, FID, VFD and HAD BG powder, respectively. CONCLUSION: VFD had the highest preservation of color, l‐ascorbic acid and chlorophyll compared to HAD, SHAD and FID. SHAD shortened the drying time and delayed the degradation of l‐ascorbic acid and chlorophyll during storage. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The heating area of the material is large and the thermal efficiency is high, but it is necessary to control the suitable drying temperature of different medicinal materials to preserve the effective ingredients. Different kinds of Chinese medicine need different drying conditions to fulfill good drying requirements. Natural drying in the shade is one of the traditional drying methods, which takes a long time and is easily affected by the weather. The water volatilizes slowly. It is prone to mildew and discoloration during the drying process. However, it can better preserve the volatile oil components of Chinese medicine. The hot-air drying machine has lower requirements. The medicinal materials have a large heating area and high thermal efficiency, but it is necessary to control the appropriate drying temperature of different medicinal materials in order to preserve the active ingredients of the medicinal materials; it is not suitable for medicinal materials that stick and bind easily. The microwave drying method possesses superiority in drying some valuable medicinal materials such as Renshen (Radix et Rhizoma Ginseng) and Lurong (Cornu Cervi Pantotrichum), and the effective ingredients are preserved at a high degree; it can also achieve the purpose of killing enzymes and protecting glycosides and have a good bactericidal effect, but it is not suitable for Chinese medicines containing heat-sensitive ingredients, because it will destroy most of the proteins, amino acids, and peptides of Chinese medicine and result in the loss of efficacy. The far-infrared drying method is suitable for drying thin-layer medicinal materials and is friendly to the environment. Freeze-drying can preserve the active ingredients very well and greatly retain the efficacy, but it has obvious limitations in preserving some Chinese medicinal materials that need to kill enzymes and protect glycosides; besides, the cost is relatively high and the drying time is long.

Industrially, the use of far-infrared (FIR) as a heat source for drying daylily presents some issues, such as high energy consumption and large loss of nutrients. The use of mid-infrared (MIR) was performed to study the drying of daylily to explore its advantages, with the FIR drying as a comparison. Drying models were established by the drying kinetics, and the changes of nutrition, rehydration ratio (RR) and water migration pattern were researched. The results showed the best-fitting drying model was the Modified Henderson and Pabis model. Under the same temperature, compared with FIR drying, the drying time of MIR drying was shortened by 50%, the effective moisture diffusivity (Deff) was increased by 103%, the drying activation energy (Ea) was reduced by 10%, the reducing sugar and ascorbic acid retention rate was increased by 13.9% and 9.7%, respectively. The MIR drying had better RR and water migration characteristics. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: The current typical drying methods for red ginseng are sun drying and hot-air drying. The purpose of this study was to investigate drying characteristics of red ginseng by using far-infrared drying. Methods: The far-infrared drying tests on red ginseng were conducted at two drying stages: (1) high temperature for 24 h drying and (2) low temperature drying until the final moisture content was 13 ± 0.5% (wet basis). The high temperature drying stage included three drying chamber temperature conditions of 60°C, 65°C, and 70°C. The low temperature drying stage was conducted at temperatures of 45°C and 50°C. Drying characteristics were analyzed based on factors such as drying rate, color changes, energy consumption, and saponin content. The results were compared with those of the hot-air and sun drying methods. Results: The results revealed that increases in drying temperature caused a decrease in drying time and energy consumption for far-infrared drying. The saponin content decreased under all drying conditions after drying, the highest value (11.34 mg/g) was observed at drying conditions of 60∼50°C. The sun drying condition showed the lowest color difference value when compared with far-infrared and hot-air drying. Conclusion: The far-infrared drying showed a faster drying rate, higher saponin content, lower color difference value, and a decrease in energy consumption than seen in hot-air drying.

This paper describes the experimental results on the drying of the apple slices by infrared radiation under vacuum condition. The investigation of vacuum far-infrared drying processes was conducted on the experimental set-up that is designed to imitate industrial batch dryer. The experimental conditions have been chosen such that heaters temperature and absolute chamber pressure have been in the range used on the industrial dryer. Apple slices were dried at four vacuum pressures 20, 40, 60 and 80 kP and five temperature of heatres, 120, 140, 160, 180 and 200ºC which were kept constant during the single experiments. Based on experimental drying data, it was found that the drying time decreased with an increase of temperature of heaters and the decrease in the absolute chamber pressure. It was also concluded that the influence of the temperature of heaters has more significant effect on reducing of the drying time than the vacuum pressure.

• MTP affected qualities of instant Tremella fuciformis soup. • FD-VD, FD-FIRD, FD-HAD were employed to dry Tremella fuciformis soup. • FD-VD retained appearance quality and reconstitution behaviors of samples. • Rheological properties were correlated with polysaccharide content in liquid soup. • GC–MS profiles of rehydrated soup differed from fresh soup. The textural, rheological and flavor reconstitution behaviors of rehydrated instant Tremella fuciformis soup, treated by combined freeze drying + vacuum drying (FD-VD), freeze drying + far-infrared drying (FD-FIRD) and freeze drying + hot air drying (FD-HAD), were evaluated and compared with fresh soup. Moisture content transfer point (MTP) of 15 ± 2% was selected according to products quality and drying time. Instant soup treated by FD-VD showed lower shrinkage and looser structure compared with that of FD-FIRD and FD-HAD. After rehydration, FD-VD soup showed the best reconstitution behaviors with recovery rate of TSS, soluble protein and polysaccharide content up to 87.61%, 83.52%, 79.08% respectively. Besides, FD-VD rehydrated soup, with the highest polysaccharide content, showed similar rheological properties to the fresh soup. FD-VD soup contained more similar aroma compounds to FD sample measured by GC–MS, while FD-FIRD and FD-HAD generated new aldehydes, ketones and hydrocarbons, leading to unpleasant flavors. [ABSTRACT FROM AUTHOR]

Mangoes have a short shelf life because of their high-water content. This study aimed to compare the effect of three drying methods (HAD, FIRD and VFD) on mango slices to improve product quality and reduce costs. Mangoes were dried at various temperatures (50, 60, 70 °C) with different slice thicknesses (3, 5, 7, 10 mm). Results indicated that FIRD was the most cost-effective with the dried mango containing the highest sugar-acid ratio, and when the mango slices thickness was 7 mm and drying at 70 °C, the ascorbic acid content, rehydration ratio, sugar-acid ratio, and energy consumption per unit volume reached 56.84 ± 2.38 mg/100 g, 2.41 ± 0.05, 83.87 ± 2.14, and 0.53 kWh/L. Among three mathematical models, the Page model described the most satisfactory drying behaviour of mango slices in FIRD. This study provides useful information in mango processing industry and FIRD is supposed to be a promising drying method., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)

The effects of some drying techniques (hot-air drying, far-infrared drying and microwave-vacuum drying) on the qualities of longan fruit leather, as well as on the drying rate, specific energy consumption, and other properties of longan fruit leather were studied. The drying time for microwave vacuum drying was shortest and the specific energy consumption was also lowest. However, far-infrared drying gave products with the best qualities. It also reduced the drying time and specific energy consumption in comparison to hot-air drying and was found to be suitable for the production of longan fruit leather. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Tg and water state in carrot tissues were explored using DSC and NMR. [•] With increasing time, FID caused changes in the water state in dehydrated carrots. [•] FID caused a shift from free water to immobilized water in carrot tissues. [•] FID could elevate Tg values mainly by reducing immobilized water in carrot tissues. [Copyright &y& Elsevier]

A far-infrared radiation (FIR) catalytic laboratory dryer was designed by us and used to dry tomato. The kinetics of drying of tomato slices with FIR energy was dependent on both the distance from the heat source and the sample thickness. Numerical evaluation of the simplified Fick's law for Fourier number showed that the effective moisture diffusivity increased from 0.193×10-9 to 1.893×10-9 m²/s, from 0.059×10-9 to 2.885×10-9 m²/s, and, from 0.170×10-9 to 4.531×10-9 m²/s for the 7, 9, and 11 mm thick slices as moisture content decreased. Application of FIR enhanced the flavour of the dried tomatoes by 36.6% when compared with the raw ones. The results demonstrate that in addition to shorter drying times, the flavour of the products can be enhanced with FIR. Therefore, FIR drying should be considered as an efficient drying method for tomato with respect to minimization of processing time, enhancement in flavour, and improvements in the quality and functional property of dried tomatoes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate drying models and drying characteristics of Ligularia fischeri by using far-infrared drying. The far-infrared drying tests on L. fischeri were performed at air velocities of 0.6 and 0.8 m/s, and drying chamber temperatures of 40, 45, and 50°C. Four thin layer drying models were used to estimate drying curves. Drying characteristics were analyzed on the basis of drying rate, color, antioxidant activity, and contents of polyphenolics and flavonoids. The goodness of the models was estimated using the coefficient of determination, the root mean square error, and the reduced chi-square. The results revealed that increases in drying temperature and air velocity caused a decrease in drying time. The Page and Thompson models were considered suitable for the far-infrared drying of L. fischeri. After drying, the antioxidant properties of L. fischeri were decreased under all drying conditions. [ABSTRACT FROM AUTHOR]

A ring shape is commonly used for industrial process of pineapple. Unfortunately, there has been no study on modeling of pineapple rings. Therefore we developed the mathematical model of pineapple rings during combined far-infrared radiation and air convection drying to investigate the evolutions of moisture content and qualities. The drying model based on the solution of Fick's law was used to estimate moisture diffusion coefficient (D). The D values with and without taking into account shrinkage phenomenon of dried products were compared. The kinetics of dried pineapple qualities such as color, shear force ratio and shrinkage during drying also were studied. Pineapples were pretreated, cut into rings and dried at far-infrared intensities of 1-5 kW/m2 combined with air temperatures of 40-60°C and air velocities of 0.5-1.5 m/s. The D values were found to increase with increasing intensity and air temperature. The D values with shrinkage consideration were lower than the D values without shrinkage consideration for all drying conditions. The quartic model gave a better fit over the other three polynomial models for describing the color kinetics. The thin layer drying models such as Page, Henderson and Pabis, Logarithmic and Midilli-Kucuk were modified in order to describe shear force ratio (SFR) of dried pineapple. The statistically analyses from this present study indicated that modification of drying models can be used to describe the kinetics of SFR and Midilli-Kucuk's form gave a better fit over the other form. The quadratic model was better than the linear model to predict shrinkage kinetics for all four dimensions (outer radius, inner radius, thickness and volume) of pineapple rings. [ABSTRACT FROM AUTHOR]

In the current study, the influence of ultrasound pretreatment followed by far-infrared drying on the drying rate, color difference and microstructure of saffron was investigated. The effect of pretreatment duration (30 and 60 s) and drying temperature (50, 60, 70 and 80 °C) on the main chemical composition, total flavonoid, antioxidant activity and volatile flavor compounds in saffron was also evaluated. The results indicated that the total drying time decreased with the increase of pretreatment duration. Especially at 50 °C, the drying time was reduced by 21.05% after 60 s pretreatment. It could also be found that 30 s ultrasound pretreatment with far-infrared drying at 50 °C was the best combination to obtain a good quality of the dried saffron. Under this condition, the samples had the highest chemical properties and volatile compounds, including crocin Ⅰ (20.78%), crocin Ⅱ (10.41%), flavonoid content (10.84 mg/g), antioxidant scavenging activity (58.92%), and major volatile flavor components (54.52%), as well as the acceptable drying time (35 min) and low color difference (26.32). The results of this study confirmed that ultrasound pretreatment had obvious effects and could be recommended for far-infrared drying of saffron. • Combined pretreatments were investigated to improve saffron far-infrared drying. • The ultrasound pretreatments reduced the drying time of saffron. • Aldehydes and ketones are the major aroma compounds of the dried saffron. • The nutritional values were higher at 30 s pretreatment with 50 °C drying. [ABSTRACT FROM AUTHOR]

The far-infrared drying technique was used to dry Stevia rebaudiana leaves, and the drying rate, drying kinetics, the glycoside content of dried Stevia rebaudiana leaves and surface structure of the dried material were explored at different drying temperatures (45 °C、50 °C、55 °C、60 °C、65 °C), irradiation height (60 mm、120 mm、180 mm、240 mm、300 mm). Under different conditions, the moisture rate decreased and the drying rate increased significantly with the increase in drying temperature and the decrease in irradiation height, Weibull model fits the drying curves well (R2 > 0.99). The range of the estimated water diffusion coefficient D cal was 0.841 8 × 10−4–2.945 3 × 10−4 m2 s−1, and the range of the effective water diffusion coefficient D eff was 0.835 9 × 10−6–3.629 1 × 10−6 m2 s−1. The activation energy was 28.79 kJ mol−1 determined by Arrhenius equation. By comparing the glycoside content of dried products under different drying conditions, it was found that far-infrared drying could better retain the glycoside content. The drying temperature have the batter effect on active ingredients of samples when it increased from 45 °C to 55 °C, the stevioside and rebaudioside A increased from 7.01 to 7.88 mg to 7.44 and 8.58 mg, respectively. Far-infrared drying technology could increase the number of micropores on the surface and inside the materials and improve the quality of dried products. This study explored the law of water transfer during the drying process of Stevia rebaudiana leaves and provided a theoretical reference for the research and application of Stevia rebaudiana leaf drying technology. • Far-infrared technology is applied to the drying of Stevia rebaudiana leaves. • Far-infrared drying technology improves the retention rate of glycosides in Stevia rebaudiana leaves. • The effect of far infrared drying technique on the surface microstructure of Stevia leaves was explored. [ABSTRACT FROM AUTHOR]

This study aimed to explain the non-destructive prediction of water fractions in Shiitake mushrooms (Lentinus edodes) using multispectral imaging (MSI) during far-infrared drying at 70 °C for different periods. Quantitative estimation of water fractions was obtained by combining MSI with chemometrics including partial least-squares (PLS), back propagation neural network (BPNN) and least squares-support vector machines (LS-SVM). Analysis of water fraction mobility of mushroom showed different properties in response of drying process. The proportion of each water fraction corresponds with extracted spectral data of MSI. After comparing the results of different chemometrics, PLS was good for the estimation of water fractions, which showed high accuracy with R p values of 0.95, 0.92, and 0.83. Moreover, lowest RMSEP were estimated at 8.09%, 8.00% and 4.95% for free, immobilized, and bound water, respectively. The findings of this study demonstrated that MSI was an effective tool to monitor the water fractions in processed shiitake mushrooms. • Water fractions were observed at different stages of far-infrared drying of shiitake mushrooms. • Low-field nuclear magnetic resonance (LF-NMR) demonstrated maximum proportion of free water was evaporated after 60 min of drying. • A non-destructive method developed for the prediction of water fractions using multispectral imaging system (MSI). • Quantitative estimation showed high efficiency of models whereas PLS was excellent with highest Rp and lowest RMSEP values. [ABSTRACT FROM AUTHOR]

Background: The current typical drying methods for red ginseng are sun drying and hot-air drying. The purpose of this study was to investigate drying characteristics of red ginseng by using far-infrared drying., Methods: The far-infrared drying tests on red ginseng were conducted at two drying stages: (1) high temperature for 24 h drying and (2) low temperature drying until the final moisture content was 13 ± 0.5% (wet basis). The high temperature drying stage included three drying chamber temperature conditions of 60°C, 65°C, and 70°C. The low temperature drying stage was conducted at temperatures of 45°C and 50°C. Drying characteristics were analyzed based on factors such as drying rate, color changes, energy consumption, and saponin content. The results were compared with those of the hot-air and sun drying methods., Results: The results revealed that increases in drying temperature caused a decrease in drying time and energy consumption for far-infrared drying. The saponin content decreased under all drying conditions after drying, the highest value (11.34 mg/g) was observed at drying conditions of 60∼50°C. The sun drying condition showed the lowest color difference value when compared with far-infrared and hot-air drying., Conclusion: The far-infrared drying showed a faster drying rate, higher saponin content, lower color difference value, and a decrease in energy consumption than seen in hot-air drying.