The thin-layer drying characteristics of garlic slices

Integrated drying model of lychee as a function of temperature and relative humidity

Drying is a universal method applied for food preservation. To date, several models have been developed to evaluate drying kinetics. In this study, lychee was dried employing a hot air dryer, and the drying kinetics was evaluated by comparing the Newtonian model, Henderson and Pabis model, Page model, and Logarithmic model. However, temperature and relative humidity, the key driving forces for drying kinetics, are not considered by these models. Thus, an integrated drying model, as a function of temperature and relative humidity, was developed to predict the hot air-drying kinetics and mass transfer phenomena of lychee followed by the calibration and validation of the model with independent experimental datasets. The model validation consisted of Nash- Sutcliffe model coefficient (E ), coefficient of determination ( R 2 ) and index of agreement ( d ) and all of them were found close to 1 indicating perfect model fit. Besides, the developed model was applied for process optimization and scenario analysis. The drying rate constant was found as a function of temperature and relative humidity that was high at high temperature and low relative humidity. Interestingly, temperature showed a higher effect on the drying rate constant compared to relative humidity. Overall, the present study will open a new window to developing further drying model of lychee to optimize quality its quality parameters.

Mathematical modeling of thin-layer drying kinetics and moisture diffusivity study of apple slices using infrared conveyor-belt dryer

The drying features of apples at different infrared drying settings were investigated. The drying time, moisture-effective diffusion, and activation energy of infrared dried apples were measured experimentally and statistically as a function of slice thicknesses, radiation intensity, and air velocity. The infrared intensity of 0.225, 0.130, and 0.341 W/cm2 , slice thicknesses of 6, 4, and 2 mm, and airflow of 0.5, 1.0, and 1.5 m/s were used to dry apple slices. The data shows that the drying time reduced as IR increased, but airflow and slice thickness increased. Eight statistical factors were used to compare 11 alternative mathematical drying models. The experimentally acquired drying curves were matched to the thin-layer drying equations. According to the calculations, the Midilli et al. equation had the greatest (efficiency and R2 ) and lowest (χ2 , sum of squared errors, standard error of estimate, standard error, standard deviation of difference) values. As a result, this equation is the best for modeling the drying curves of apple slices across all drying circumstances. The optimum moisture diffusivity value varied from 2.59 to 9.07 × 10-10  m2 /s. The mean activation energy was determined to be 19.02-29.83 kJ/mol under various experimental conditions.

Process modeling and simulation of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood drying

This study simulate the process modeling of drying characteristics of Gmelina arborea (GmW) and Mansonia altissima (MaW) wood under the influence of various process variables such as drying time, drying temperature, and airflow velocity. GmW and MaW moisture desorption isotherms, kinetics, and thermodynamics were also studied. Five (5) thin-layer and desorption isotherm drying models were used to model the moisture ratio and water activity data from the process. According to the anatomical analysis, the GmW sample has an average lumen size of 147.44 m, indicating a high moisture content. The results showed that the Guggenheim, Anderson, and de Boer (GAB) model with the lowest sum of squared error value (0.046) demonstrated the best-fit to the experimental desorption data for GmW samples and the Henderson-P model for MaW samples, while the Demir et al. model emerged as the best kinetics model fit for describing the moisture desorption isotherm and thin-layer drying kinetics. GmW effective diffusivity (Deff) values ranged from 3.671 × 10-8 to 5.378 × 10-8 m2/s and MaW effective diffusivity (Deff) values ranged from 2.923 × 10-8 to 4.678 × 10-8 m2/s. GmW and MaW activation energies were 252.702 kJ/mol and 313.604 kJ/mol, respectively. The thermodynamic studies revealed that the heat and mass transfer coefficients varied linearly with temperature, as the change in enthalpy (ΔH) and change in entropy (ΔS) decreased while the Gibbs free energy (ΔG) increased. The results obtained from this study demonstrated that the proposed drying process modeling and simulation approach could be successfully applied to investigate the wood drying phenomena. The information can be used to reduce the drying costs and improve the wood quality.

Chemical and Thermal Treatment for Drying Cassava Tubers: Optimization, Microstructure, and Dehydration Kinetics

Perishable commodities like cassava necessitate effective postharvest preservation for various industrial applications. Hence, optimizing pretreatment processes and modeling drying kinetics hold paramount importance. This study aimed to optimize cassava pretreatment using the central composite design of a response surface methodology while also assessing microstructure and dehydration kinetics. Diverse chemical and thermal pretreatments were explored, encompassing sodium metabisulfite concentrations (0-4% w/w), citric acid concentrations (0-4% w/w), and blanching time (0-4 min). The four investigated responses were moisture content, whiteness index, activation energy (Ea), and effective moisture diffusivity (Deff). Employing five established drying models, suitability was appraised after optimal pretreatment conditions were determined. The findings revealed that moisture content ranged from 5.82 to 9.42% db, whereas the whiteness index ranged from 87.16 to 94.23. Deff and Ea ranged from 5.06 × 10-9 to 6.71 × 10-9 m2/s and 29.65-33.28 kJ/mol, respectively. The optimal pretreatment conditions for dried cassava were identified by optimizing the use of 1.31% citric acid, 1.03% sodium metabisulfite, and blanching time for 1.01 min. The microstructure indicated that particular chemical and thermal pretreatment configurations yielded particles in the shape of circular and elliptical granules. The logarithmic model provided the most accurate description of the dehydration kinetics, with the highest R2 value (0.9859) and the lowest χ2, RSME, and SSE values of 0.0351, 0.0015, and 0.0123, respectively.

The nutritional value, bioactive availability and functional properties of garlic and its related products during processing

Garlic, a common culinary spice, is cultivated and used around the globe. Consumption of garlic and its supplements reduces the risk of diabetes and cardiovascular disease and boosts the immune system with antibacterial, antifungal, anti-aging, and anti-cancer properties. Diallyl sulfide, diallyl disulfide, triallyl trisulfide, phenolics, flavonoids, and others are the most commercially recognized active ingredients in garlic and its products. In recent years, global demand for medicinal or functional garlic has surged, introducing several products such as garlic oil, aged garlic, black garlic, and inulin into the market. Garlic processing has been demonstrated to directly impact the availability of bioactive ingredients and the functionality of products. Depending on the anticipated functional qualities, it is also recommended that one or a combination of processing techniques be deemed desirable over the others. This work describes the steps involved in processing fresh garlic into products and their physicochemical alterations during processing. Their nutritional, phytochemical, and functional properties are also reviewed. Considering the high demand for functional food, this review has been compiled to provide guidance for food producers on the industrial utilization and suitability of garlic for new product development.

Combined Pulsed Vacuum Osmotic Dehydration and Convective Air-Drying Process of Jambolan Fruits

Jambolan (Syzygium cumini) is a native fruit from Asia that has adapted well to the tropical climate of the Amazonian region. However, due to its limited annual availability and high perishability, the jambolan fruit is still underexploited. Thus, this study aimed to preserve the jambolan through a combined process of pulsed vacuum osmotic dehydration (PVOD) and convective air-drying and to monitor the total phenolic contents (TPCs) and total monomeric anthocyanins (TMAs) during these processes. To this end, jambolan fruits were pretreated with increasing PVOD times. After monitoring of moisture loss, solid gain, weight reduction, water activity, TPC, and TMA, pretreated (PT) and non-pretreated (NPT) fruits underwent convective air-drying (50-70 °C). The PVOD reduced half of the water present in the fruits; nonetheless, PVOD decreased the TPC and TMA over time. The increase in air-drying temperature shortened the drying time for both NPT and PT jambolan, and PVOD reduced even further the drying time of the fruits. Moreover, the fruits pretreated and dried at 60 °C showed promising results, potentially being a good alternative to extend the fruit's shelf life and make it available throughout the year.

Capsular Exopolysaccharides from Two Streptococcus thermophilus Strains Differ in Their Moisture Sorption Behavior

Streptococcus thermophilus is a species frequently used in the manufacture of fermented milk. Apart from acid production, some strains additionally synthesize exopolysaccharides (EPS) which contribute to texture improvement and syneresis reduction, both being attributable to the EPS's high water binding capacity. There are two different types of EPS that may be produced, namely free exopolysaccharides (fEPS) which are secreted into the medium, and capsular EPS (cEPS) which remain attached to the bacterial cell wall. This study aims to analyze their individual contribution to techno-functional properties of fermented milk by determining the moisture sorption behavior of isolated fEPS and cell-attached cEPS from two S. thermophilus strains separately: ST-1G, a producer of non-ropy fEPS and cEPS, and ST-2E, a producer of ropy fEPS and cEPS. Differences in moisture load and sorption kinetics, determined for the first time for microbial EPS, were related to structural and macromolecular properties. The observed data are discussed by using previously published data on the physical properties of stirred fermented milk produced with these two strains. ST-1G EPS showed a higher cEPS fraction, a higher moisture load and slower moisture desorption than EPS produced by ST-2E, thus contributing to lower syneresis in fermented milk. For ST-2E, higher gel viscosity was related to a higher intrinsic viscosity and molecular mass of the ropy fEPS. Both strains produced complex EPS or EPS mixtures with clearly different molecular structures.

The Temperature Influence on Drying Kinetics and Physico-Chemical Properties of Pomegranate Peels and Seeds

Pomegranate is a fruit desirable for its nutritional and medicinal properties which has a great industrial potential that is yet under-explored. Notable for its integral use, the peels are used in medicinal infusions and the seeds consumed without restrictions. In this sense, the objective of this work is to determine the drying kinetics of pomegranate peels and seeds in a hot air circulation oven, at temperatures of 50, 60, and 70 °C, adjust mathematical models to experimental data, determine the effective diffusivities and thermodynamic properties of the process and the physicochemical characteristics of peels and seeds of fresh pomegranates and in their flours. Twelve models were used to adjust the drying kinetics, obtaining better results with the Diffusion Approximation model, Verma, and modified Henderson and Pabis. The effective diffusivities were well represented by an Arrhenius equation, with activation energies of 31.39 kJ/mol for seeds and 10.60 kJ/mol for peels. In the drying process, the seeds showed higher values of enthalpy, entropy, and Gibbs free energy concerning peels. Pomegranate peel and seed flours have proximal composition and distinct physicochemical characteristics, with high fiber, carbohydrate, and energy content. In addition, peel flours stand out for their mineral content, and seed flours do for their lipid and protein content.

The Effect of Different Drying Methods on Bioactive and Nutrition Contents of Bee Bread and Mathematical Modeling of Drying Characteristics

In this study, the aim was to determine the effect of different drying methods (with microwave and hot air) on the color, nutrient and bioactive contents of fresh bee bread. Drying characteristics were also investigated. Microwave and hot air drying were applied at different microwave powers and temperatures, respectively. Lower moisture ratios and highest effective diffusion coefficients were obtained with microwave drying in a shorter time. The Midilli model was found to be the most suitable thin-layer drying model for both methods. Regardless of the drying conditions, moisture, ash, protein, carbohydrate, and lipid proportions were observed to vary in the ranges of 4.9-8.2 %, 1.61-2.67 %, 17.47-32.54 %, 39.92-60.84 %, and 7.10-8.89 %, respectively. The lowest color difference was obtained for the sample dried at 210 W. As a result, it was determined that microwave drying is more suitable for preserving the nutritional and bioactive content of bee bread during drying.

Controlled Germination of Faba Beans: Drying, Thermodynamic Properties and Physical-Chemical Composition

The objective of this work was to determine the drying kinetics and the thermodynamic properties of the drying process of germinated seeds from faba beans of the Olho-de-Vó Preta (OVP), Raio-de-Sol (RS) and Branca (B) varieties. Additionally, the physicochemical properties of the germinated seeds and subsequent dried flours were determined. A thin layer of seeds were dried using a convective dryer at temperatures of 50, 60, 70 and 80 °C. Mathematical models were applied to the drying experimental data. The samples were further characterized for water content, water activity, ash, pH, alcohol-soluble acidity, total and reducing sugars, proteins, and starch. Page and Midilli models revealed the best predictions of the drying kinetics for all evaluated conditions. The effective diffusion coefficient increased with increasing temperature and presented magnitude in the order of 10−9 m²/s. The activation energy presented results in the range of 19 and 27 kJ/mol, falling within the range reported for agricultural products. The entropy and enthalpy values were higher in the OVP, followed by RS, higher than in the B variety. The increase in drying temperature resulted in a reduction of enthalpy and entropy and an increase in Gibbs free energy, indicating that the drying process is endothermic and requires external energy. Samples have acidic pH and acidity decreased with drying; the RS and B varieties had higher sugar contents; the B variety had the highest protein contents, and these were obtained from the in natura germinated samples; in the B variety the highest starch content was obtained. All flours showed good characteristics, presenting themselves as an alternative for diversifying the supply of beans.

MODELAGEM MATEMÁTICA E PROPRIEDADES TERMODINÂMICAS DA SECAGEM CONVECTIVA DA POLPA DE TUCUMÃ (Astrocaryum aculeatum)

A polpa de tucumã possui potencial para utilização industrial. Entretanto, o elevado conteúdo de umidade limita o seu uso. Assim, objetivou-se secar convectivamente a polpa de tucumã, a qual foi desidratada na espessura de 4 mm, nas temperaturas de 30, 40, 50 e 60 °C, com monitoramento da perda de umidade até equilíbrio higroscópico. Verificou-se que o aumento de temperatura reduziu os teores de umidade de equilíbrio. As taxas de secagem foram maiores em maiores temperaturas e teores de umidade. Os modelos de Dois termos (30 a 50 °C) e Midilli (60 °C) foram os mais adequados para descrever a secagem da amostra. Os coeficientes de difusão efetivos de umidade ficaram compreendidos entre 0,98 × 10-10 e 4,20 × 10-10 m2 s-1 e sua dependência com a temperatura foi descrita pela equação de Arrhenius, com energia de ativação de 42,15 kJ mol-1. As propriedades termodinâmicas evidenciaram um processo endergônica.

Analysis of Volatiles of Rose Pepper Fruits by GC/MS: Drying Kinetics, Essential Oil Yield, and External Color Analysis

Condiments and culinary supplements are subjected to long-term storage and may undergo physical, chemical, and biological changes that can influence their quality. Thus, the objective of the present study was to analyze the drying kinetics of rose pepper (Schinus terebinthifolius Raddi) fruits in an oven with forced air circulation at different temperatures, namely, 45, 55, 65, and 75°C, and determine the effective diffusion coefficient and activation energy using different mathematical models. Furthermore, the effects of the different drying temperatures were analyzed for external color parameters and yield of essential oil contents by gas chromatography coupled to a mass spectrometer. Of the ten models used for fitting, Thompson’s model was one with the best fitting to represent the drying of rose pepper fruits. The diffusion coefficient increases with the elevation of drying air temperature, described by the Arrhenius equation, with activation energy of 53.579 kJ·mol−1. The color of the fruits decreased in lightness (L ${}^{\ast }$ ) with the increase in temperature. Of the thirty-eight terpenes identified, α-pinene and cis-ocimene were the most abundant, with the overall highest yield being found at a drying temperature of 45°C.

The effect of high-power ultrasound pretreatment on drying efficiency and bioactive compounds of chokeberry (Aronia melanocarpa L.)

Chokeberry (aronia) fruit is a rich source of bioactive compounds with various health benefits. However, it has a limited shelf life and a firm (tight) structure that makes it difficult for moisture transfer during drying. Therefore, the aim of the study is to investigate the effects of high-power ultrasound pretreatment (550 W, 30 min) and air drying temperature (65, 70 and 75 °C) on the drying rate and bioactive compounds of chokeberry fruit. Accordingly, chokeberries were dried directly or after ultrasound pretreatment, and the retention rate of bioactive properties, i.e., total phenolic, flavonoid and monomeric anthocyanin contents along with antioxidant capacity values, were examined. The required time for drying as well as the activation energy values were significantly lower in ultrasound treated samples. Logarithmic and Midilli models exhibited the best fit for drying kinetics of samples. The pretreatment led to significantly lower moisture content and a_w values. Compared to fresh sample, the highest retention rate for some bioactive properties was found in ultrasound pretreated sample dried at 75 °C. The ultrasonication also reduced the electricity consumption (kWh) in all temperature levels of drying operations. As a conclusion, the ultrasound pretreatment prior to drying had dual role by facilitating drying kinetics and by providing higher bioactive contents.

Assessment of Drying Kinetics, Textural and Aroma Attributes of Mentha haplocalyx Leaves during the Hot Air Thin-Layer Drying Process

Since Mentha haplocalyx leaves are rich in bioactive constitutes, particularly volatile compounds, there are higher demands for high-quality dried medicinal and aromatic peppermint products. This study aimed to assess the drying kinetics of hot air thin layer drying Mentha haplocalyx leaves and exploring the effects of hot air-drying temperatures on the textural properties and sensory quality. According to our results, the Midilli model is the best model representing the hot air-drying process. The effective moisture diffusivity (Deff) and activation energy (Ea) of the hot air-drying process were determined as 7.51 × 10⁻⁹–3.03 × 10⁻⁸ m²/s and 57.98 KJ/moL, respectively. The changes of textural and aromatic profiles of dried Mentha haplocalyx leaves were subsequently evaluated by the SEM, GC–MS and E-nose technology. Changes in leaf cellular membrane structures were observed in this study, indicating that the loss of moisture content induced the shrinkage of leaf cells during the hot air-drying process. Moreover, the altered profile of volatile compounds was identified at the different drying temperatures. As a result of the GC-MS analysis, increasing the content of D-carvone from 61.89%, 69.25% and 78.2% resulted in drying temperatures of 35 °C, 45 °C and 55 °C, respectively; while a decreasing trend of other volatile compounds, including D-Limonene, cineole and l-caryophyllene was detected as drying temperature elevated. Finally, the aromatic profile was evaluated by E-nose, and results of the flavor radar fingerprint and PCA showed that aromatic profiles were significantly altered by the drying process. The overall results elucidated that the hot air thin layer drying at 35 °C efficiently improved the final quality of dried Mentha haplocalyx leaves by maintaining flavor properties.

Effect of microwave, infrared, and convection hot-air on drying kinetics and quality properties of okra pods

Okra pods were dried using the following drying regimes; microwave (MWD), infrared (IRD) and convective hot-air drying (CHD). The objective of this investigate was to report the influences of drying methods on okra quality under different drying conditions. Data analysis showed that rehydration ratio and colour change increased with increase in drying air temperature and air velocity while specific energy consumption and shrinkage ratio decreased with increase in drying air temperature under (CHD). The rehydration ratio and colour of dried okra increased with increase in both infrared intensity but it also increased with a decrease in air velocity under (IRD). In the MWD method, drying time, specific energy consumption and shrinkage ratio decreased with increases in microwave power while the rehydration ratio and colour increased. Optimum drying period, specific energy consumption, colour, shrinkage and rehydration ratio were obtained for microwave drying. The model of Midilli et al. is the greatest for describing the drying curves of okra under all the drying processing conditions.

Development and validation of a heated drying air diffusion system to optimize rotary dryers and final coffee quality

The final quality of pre-processed coffees is influenced by the applied drying technology. Thus, the aim of the study was to develop and validate a heated air flow diffusion system to optimize and reduce the drying time of rotary dryers and improve the final quality of coffee. Computational fluid dynamics was used for the simulation of the air fluid dynamics in the combustion chamber of the heat generator. It was observed that the energy losses in the upper and lower walls of the heat generator chamber were higher with an increase in the convective heat transfer coefficient. It was found that the rate of fluid flow presented a fully developed profile, in which the higher speed value was found in the central region of the outlet. The reduction in moisture content during coffee drying was directly proportional to the increase in temperature. The Midilli model shows the best fit to describe the drying curves of the coffee. The effective diffusion coefficient increases with increasing temperature of the drying air. It was observed that the adjustments of the fluid dynamics in the burning of gas and the adaptation of the diffuser system significantly influenced the drying time and final quality of naturally processed and pulped coffees. In conclusion, the adapted technological set, a rotary dryer with gas heating and diffusion of heated air, had a high performance in the final quality of the coffee, and for this reason it is recommended to producers and the industry.

Utilization of Cumbeba (Tacinga inamoena) Residue: Drying Kinetics and Effect of Process Conditions on Antioxidant Bioactive Compounds

The residue generated from the processing of Tacinga inamoena (cumbeba) fruit pulp represents a large amount of material that is discarded without proper application. Despite that, it is a raw material that is source of ascorbic acid, carotenoids and phenolic compounds, which are valued in nutraceutical diets for allegedly combating free radicals generated in metabolism. This research paper presents a study focused on the mathematical modeling of drying kinetics and the effect of the process on the level of bioactive of cumbeba residue. The experiments of cumbeba residue drying (untreated or whole residue (WR), crushed residue (CR) and residue in the form of foam (FR)) were carried out in a fixed-bed dryer at four air temperatures (50, 60, 70 and 80 °C). Effective water diffusivity (Deff) was determined by the inverse method and its dependence on temperature was described by an Arrhenius-type equation. It was observed that, regardless of the type of pretreatment, the increase in air temperature resulted in higher rate of water removal. The Midilli model showed better simulation of cumbeba residue drying kinetics than the other models tested within the experimental temperature range studied. Effective water diffusivity (Deff) ranged from 6.4890 to 11.1900 × 10-6 m2/s, 2.9285 to 12.754 × 10-9 m2/s and 1.5393 × 10-8 to 12.4270 × 10-6 m2/s with activation energy of 22.3078, 46.7115 and 58.0736 kJ/mol within the temperature range of 50-80 °C obtained for the whole cumbeba, crushed cumbeba and cumbeba residue in the form of foam, respectively. In relation to bioactive compounds, it was observed that for a fixed temperature the whole residue had higher retention of bioactive compounds, especially phenolic compounds, whereas the crushed residue and the residue in the form of foam had intermediate and lower levels, respectively. This study provides evidence that cumbeba residue in its whole form can be used for the recovery of natural antioxidant bioactive compounds, mainly phenolic compounds, with the possibility of application in the food and pharmaceutical industries.

Optimization of ohmic heating-assisted osmotic dehydration as a pretreatment for microwave drying of quince

In this study, the ohmic heating system was used as a novel application for osmotic dehydration of quince. After osmotic dehydration, samples were dried by microwave. In this regard, the effects of process variables such as electrical field strengths (20, 30 and 40 V/cm), holding time (10, 20 and 30 minutes), microwave power (90, 180 and 270 W) and sucrose concentration (0%, 25% and 50%) on dielectric constant, dielectric loss factor, rehydration ratios, total phenolic compounds and color values were investigated by response surface methodology (RSM). Optimum conditions were found as 40 V/cm electrical field strength, 30 min holding time, 16.67% sucrose concentration and 270 W microwave power. Total phenolic content, rehydration ratio, color differences and dielectric properties of the novel method were found to be higher than that of control. Moreover, Midilli and Wang & Sing models gave the superior fit to the moisture ratio data obtained during drying.

Quantifying the influencing factors and multi-factor interactions affecting cadmium accumulation in limestone-derived agricultural soil using random forest (RF) approach

Cadmium (Cd) is a highly toxic heavy metal that occurs widely in the environment and poses extensive threats to human health, animals, and plants. This study aims to identify and apportion multi-source and multi-phase Cd pollution from natural and anthropogenic inputs using ensemble models that include random forest (RF) in agricultural soils on Karst areas. The contributions of natural and anthropogenic factors to Cd accumulation were quantitatively assessed using the RF machine learning method. The results revealed that the main influencing factors were pH, organic carbon (C_org), and elevation. Moreover, the interaction effects of pH and C_org on distance and elevation were also quantified and visualised. It is observed that pH and C_org had stronger effects on soil Cd concentration than that of distance when pH > 7.02 and C_org > 1.53. In other words, higher Cd content in the soil along roadways may be caused by the interaction of distance, pH and C_org, with pH and C_org playing the dominant role in our case. Moreover, the maximum contribution of a single factor, elevation, to Cd concentration was about 0.13 mg/kg, and its interactions reached 1.082 mg/kg and 0.83 mg/kg, respectively, when combined with pH and C_org at 194.0 m. However, with increasing elevation, pH and C_org gradually took over the leading roles. This result not only gives us a quantitative understanding of the relationship between the factors that affect soil cadmium accumulation, but also provides an accurate method for source apportionment of heavy metals in soil.

Solar drying of residue from Brazil nut processing

Abstract Brazil nuts are often used for direct consumption or in the preparation process of water-soluble extract. After obtaining the water-soluble extract, a large amount of Brazil nut residues with good sensory characteristics are generated. Thus, this study aimed to dry Brazil nut processing residues in layers with different thicknesses in a direct solar dryer as well as by direct exposure to the sun, in order to fit different mathematical models to the experimental data of drying kinetics, and calculate the drying rates and effective diffusivity. The drying procedures began at 9 a.m. on a concrete base, for samples dried by direct exposure to the sun, and in a solar dryer constructed with expanded polystyrene foam zinc plated and a glass cover. The mass loss of the samples was monitored by weighing at regular times until the hygroscopic equilibrium was obtained. The direct solar dryer had temperatures about 80% higher than those recorded in the open environmental air temperature. Drying rates were higher in dehydrations performed in the solar dryer compared to the drying by exposure to the sun. The Midilli model was selected as the most adequate for predicting the drying of the samples under all experimental conditions, showing coefficients of determination above 0.99. The effective diffusion coefficients of moisture were higher in samples dehydrated in the solar dryer when compared to those dried by exposure to the sun. Regarding the research conducted under the experimental conditions of this study, the performance of the solar dryer to dry Brazil nut processing residues was satisfactory.

An improved protocol for natural convective drying of pumpkin

The most effective way to preserve agricultural product is drying. However, vegetable drying is an energy-consuming procedure. Convective drying is the mode considered in this work. The study intends to explore a new way of pumpkin drying, which reduces drying time and minimizes heat consumption. The study considers pumpkin thin slices and pumpkin samples with cubic shape. The samples were subjected to free convection airflow at different temperatures (40 °C, 46 °C, 52 °C, and 60 °C) for each run. A varying airflow temperature was also considered. Airflow velocity was generated by buoyancy forces for each temperature. Drying curves were plotted and fitted to the widely used thin-layer drying models. The modified Page model came out as the best-fitted model. The effective diffusivity coefficient was determined for each case using the slope moisture curve. It appeared that diffusivity was high and drying time was short, for high temperature. Drying processes for slice configuration and cube configuration showed that the latter was more efficient. When applying the regime of increasing temperatures to the cubic samples, data analysis showed that effective diffusivity was higher during the third step in comparison to all the other drying temperatures and the total drying time was similar to that obtained at drying regime on high temperature. With this procedure, the final consumed energy was much less and the time was shorter.

Modelagem e propriedades termodinâmicas da secagem do epicarpo, mesocarpo e endocarpo do tucumã (Astrocaryum aculeatum)

Resumo O tucumã é um fruto amazônico, possui alto poder nutricional e é utilizado em diversos segmentos econômicos. Portanto, estudos para a redução de umidade devem ser realizados para o aumento do tempo de prateleira deste fruto. Este trabalho tem como objetivo realizar o estudo de secagem do epicarpo (casca), mesocarpo (polpa) e endocarpo (amêndoa) do tucumã nas temperaturas de 60 ºC, 70 ºC e 80 ºC. Foi observado que o aumento da temperatura reduziu o tempo de queda da razão de umidade do epicarpo, mesocarpo e endocarpo. Modelos matemáticos foram utilizados para estimar dados experimentais e foram calculadas propriedades termodinâmicas do processo. Baseado no maior R2 e o menor SE e DQM, o modelo Logístico apresentou melhor ajuste para cinética de secagem dentre os avaliados, estimando energia de ativação de 39,50 kJ mol-1, 46,62 kJ mol-1 e 17,76 kJ mol-1 para o epicarpo, mesocarpo e endocarpo, respectivamente. Os resultados das propriedades termodinâmicas mostraram que a entalpia (ΔH) caracteriza a secagem como um processo endotérmico. A entropia (ΔS) diminui com o aumento da temperatura. Os valores da energia de Gibbs são positivos, ou seja, o processo é não espontâneo e necessita de energia externa para difusividade da água no ar.

Description of Cumbeba (Tacinga inamoena) Waste Drying at Different Temperatures Using Diffusion Models

One approach to improve sustainable agro-industrial fruit production is to add value to the waste generated in pulp extraction. The processing of cumbeba (Tacinga inamoena) fruits generates a significant amount of waste, which is discarded without further application but can be a source of bioactive compounds, among other nutrients. Among the simplest and most inexpensive forms of processing, convective drying appears as the first option for the commercial utilization of fruit derivatives, but it is essential to understand the properties of mass transfer for the appropriate choice of drying conditions. In this study, cumbeba waste was dried at four temperatures (50, 60, 70 and 80 °C). Three diffusion models were fitted to the experimental data of the different drying conditions. Two boundary conditions on the sample surface were considered: equilibrium condition and convective condition. The simulations were performed simultaneously with the estimation of effective mass diffusivity coefficients (D_ef) and convective mass transfer coefficients (h). The validation of the models was verified by the agreement between the theoretical prediction (simulation) and the experimental results. The results showed that, for the best model, the effective mass diffusivities were 2.9285 × 10⁻⁹, 4.1695 × 10⁻⁹, 8.1395 × 10⁻⁹ and 1.2754 × 10⁻⁸ m²/s, while the convective mass transfer coefficients were 6.4362 × 10⁻⁷, 8.7273 × 10⁻⁷, 8.9445 × 10⁻⁷ and 1.0912 × 10⁻⁶ m/s. The coefficients of determination were greater than 0.995 and the chi-squares were lower than 2.2826 × 10⁻² for all simulations of the experiments.

Effects of ultrasonic vacuum drying on the drying kinetics, dynamic moisture distribution, and microstructure of honey drying process

The aim of this study was to study the strengthening effect of ultrasonic vacuum technique on the drying kinetics, moisture distribution, and microstructure of honey using low-field nuclear magnetic resonance and scanning electron microscopy. Results showed that ultrasonic vacuum drying technique could substantially shorten the drying time from 600 to 60 min, compared with vacuum drying. The sonochemical effects of ultrasonic vacuum drying were enhanced with the increased ultrasonic power and were more obvious in the initial stage of drying. This finding is consistent with the effective water diffusion coefficient results. The non-linear fitting analysis of experimental data on seven kinds of thin-layer drying mathematical models showed that logarithmic model is more suitable for describing the law of moisture change in honey during ultrasonic vacuum drying than the other models because of its higher regression coefficient value (≥0.99) and smaller reduced chi-square and root mean square error values (≤0.01). In addition, low-field nuclear magnetic resonance results showed that the increase in ultrasonic power accelerated the migration of bound water to immobilized water in honey samples. Scanning electron microscopy results showed that the porous structure formed by increasing the ultrasonic power is also conducive to the rapid migration and drying of moisture. In conclusion, ultrasonic vacuum drying technique is an effective and safe way for drying viscous materials compared with vacuum drying technique.

Mathematical Modeling, Moisture Diffusion and Color Quality in Intermittent Microwave Drying of Organic and Conventional Sweet Red Peppers

The aims of this research were to evaluate the influence of intermittent microwave drying on the moisture diffusion and color qualities of organically and conventionally grown sweet red peppers and mathematically express drying kinetic data. Pepper samples of 150 g were dried at 150, 300 and 450 W using a microwave oven. Results showed that intermittent microwave drying at 450 W occurred mainly in the falling rate period, whereas drying at lower powers resulted in relatively longer constant rate periods for both peppers types. The Midilli model provided the best fit for all data. The moisture diffusivity (Deff) values of organic and conventional samples ranged from 59.69 × 10−10 to 182.01 × 10−10 m2s−1 and from 59.11 × 10−10 to 181.01 × 10−10 m2s−1, respectively, and the difference was insignificant. The pre-exponential factor for the Arrhenius equation (D0) and activation energy (Ea) values were almost identical for both product types. Overall, organic or conventional growing did not alter the structural features related to the heat transfer properties. Intermittent microwave drying at 150 and 300 W for organic peppers and 150 W for conventional peppers gave the highest ΔL*, Δa* and a*/b* values, producing the most bright and red pepper powders. Thus, these treatments can be used to produce higher color quality powders.

New Potent 5α- Reductase and Aromatase Inhibitors Derived from 1,2,3-Triazole Derivative

This work describes the utility of pyrazole-4-carbaldehyde 1 as starting material for the synthesis of a novel potent series of 5α-reductase and aromatase inhibitors derived from 1,2,3-triazole derivative. Condensation of 1 with active methylene and different amino pyrazoles produced the respective Schiff bases 2-4, 8 and 9. On the other hand, 1 was reacted with ethyl cyanoacetate and thiourea in one-pot reaction to afford the pyrazolo-6- thioxopyridin-2-[3H]-one (10). Moreover, α-β unsaturated chalcone derivative 11 was prepared via the reaction of compound 1 with P-methoxy acetophenone, which in turn reacted with each of ethyl cyanoacetate, malononitrile, hydrazine hydrate, and thiosemicarbazide to afford the corresponding pyridine and pyrazole derivatives 13, 14, 17, and 20. The structure of newly synthesized compounds was characterized by analytical and spectroscopic data (IR, MS and NMR). All new compounds were evaluated against 5α-reductase and aromatase inhibitors and the results showed that many of these compounds inhibit 5α-reductase and aromatase activity; compound 13 was found to be the highest potency among the tested samples comparing with the reference drugs.