Rehydration of Rosa rubiginosa Fruits Dried with Hot Air

The effect of perforation, drying temperature, and rehydration temperature on the rehydration kinetics of Rosa rubiginosa fruits was investigated. Before drying, half of the fruit sample was perforated three times at equidistant points along the equatorial plane of the fruit, in order to speed up the drying process. Samples were dried at various air temperatures (60, 70, and 80°C), with an air velocity of 5 m/s and 5% relative humidity. Then, dried samples were rehydrated at different temperatures (20, 40, 60, and 80°C). The rehydration kinetics was fitted by two empirical models, Peleg and Weibull, and both represented the phenomenon well, in perforated and nonperforated fruits. Regardless of the drying temperature, the higher the rehydration temperature of rose hip fruits, perforated or not, the higher the water absorption capacity. Temperature dependence of the kinetic parameters was E_a = 47.5 kJ/mol (Peleg) and 55.9 kJ/mol (Weibull) for nonperforated fruits and E_a = 40.1 kJ/mol (Peleg) and 45.5 kJ/mol (Weibull) for perforated fruits; thus, perforated fruits were influenced more by rehydration temperature than nonperforated fruits. Perforated fruits rehydrated 30% faster than nonperforated fruits.     

Impact of the Instant Controlled Pressure Drop Treatment on Hot Air Drying of Cork Granules

Instant controlled pressure drop (DIC) is known to enhance drying kinetics of cork granules. The overall kinetics is limited by the internal mass transfer. Hence, the drying kinetics carried out at 50, 60, and 70°C allows the effective diffusivity values to be determined as 2.63E-10 to 4.50E-10 and 4.34E-10 to 6.99E-10 m² s^?1 for untreated and DIC-treated cork granules, respectively. Because the temperature dependence is represented by an Arrhenius-type relationship, the activation energy values are determined as 25.29–48.12 kJ/mol and 32.43–43.98 kJ/mol for untreated and DIC-treated cork granules, respectively.     

Thin-Layer Drying of Green Peas and Selection of a Suitable Thin-Layer Drying Model

The thin-layer drying of three varieties of green peas was carried out in hot air-drying chamber using an automatic weighing system at five temperatures (55–75°C) and air velocity of 100 m/min. The green peas were blanched and sulphited before drying. The variety Pb-87 dried at 60°C was judged to be best for quality on the basis of sensory evaluation and rehydration ratio. The Thomson model was found to represent thin-layer drying kinetics within 99.9% accuracy. The effective diffusivity was determined to be 3.95 × 10^?10 to 6.23 × 10^?10 m²/s in the temperature range of 55 to 75°C. The activation energy for diffusion was calculated to be 22.48 kJ/mol. The variation in shrinkage exhibited a linear relationship with moisture content of the product during drying. The Dincer number at drying air temperature 60°C and drying air velocity 100 m/min was determined to be 2,838,087. The difference between temperatures of drying air and that of green pea kernels was found to decrease with drying time for all the drying temperatures taken for investigation.     

Process-Based Drying Temperature and Humidity Integration Control Enhances Drying Kinetics of Apricot Halves

The effects of drying temperature (50, 60, and 70°C) and absolute humidity (65, 90, 115, 140 g/kg at the initial stage) on drying kinetics and color attributes of apricot halves under process-based drying temperature and humidity integration control (PDTHIC) were investigated. Results indicated that appropriate PDTHIC could reduce the drying time by 18.75% compared to the control group. The absolute humidity parameter should be controlled well rather than continuously dehumidify for traditional practices. The moisture effective diffusivity (D_eff) at 70°C presented drastic fluctuations with increasing absolute humidity parameters, calculated using the Weibull distribution model. The activation energy (E_a) of samples treated by continuous dehumidification and PDTHIC were 31.40 and 74.18 kJ/mol, respectively. The variation trend of color parameters was different from the conventional hot air drying probably due to the dehydration mechanism. Observation of the microstructure of the dried samples indicated that the PDTHIC process can enhance the drying rate of apricot through generating a larger pore network compared to continuous dehumidification at the same temperature. The findings of the current work clearly indicated that process-based drying temperature and humidity integration control enhances the drying kinetics of apricot halves, leading to a promising technology for energy savings.     

DRYING CHARACTERISTICS OF RED CHILLI

ABSTRACT

Red chilli is widely consumed as a food additive throughout the world. It is blanched/treated to minimize quality loss during processing. This paper reports on various pre-treatments applied before drying and their influence on drying kinetics as well as product quality. Inactivation of peroxidase enzyme was achieved by blanching chillies at 90°C for 3 min in hot water. The physical appearance of the dried product was found to be the best when the blanched samples were soaked in gum acacia solution (0.2% m/v) for 15 min at room temperature. The pre-treated chillies were dried in a tray dryer at selected temperatures (55, 60, 65 and 70°C). Results indicated that drying took place in the falling rate period; the drying kinetics were adequately described by the Page's model. The activation energy for drying was determined to be 41.95 and 41.06 kJ/mol respectively, for blanched and gum-treated chillies. Total pigment content decreased while non-enzymatic browning increased with increase in drying air temperature.     

Thermal Degradation Kinetics of Carotenoids in Palm Oil

In the present work, a detailed study is performed for carotene thermal degradation in palm oil at four temperatures ranging from 170 to 230 °C. The heating process was carried out with injection of nitrogen, and the samples were collected every 20 min during a total heating period of 140 min. HPLC analysis was conducted to monitor the carotenoids and tocols variations over the heating time at each temperature. The experimental data were then compared to literature data concerning carotenoids thermal degradation. The thermal degradation kinetics of carotenoids in palm oil followed an order superior to 1. The dependence of constant rates with temperature obeyed the Arrhenius relationship. The activation energy for the carotenoids thermal degradation in palm oil was found to be 109.4 kJ/mol.     

Hot-Air Drying and Rehydration Characteristics of Red Kidney Bean Seeds

The effects of pretreatments such as citric acid and hot water blanching and air temperature on drying and rehydration characteristics of red kidney bean seeds were investigated. Drying experiments were carried out at four different drying air temperatures of 50°C, 60°C, 70°C, and 80°C. It was observed that drying and rehydration characteristics of bean seeds were greatly influenced by air temperatures and pretreatments. Four commonly used mathematical models were evaluated to predict the drying kinetics of bean seeds. The Weibull model described the drying behaviour of bean seeds at all temperatures better than the other models. The effective moisture diffusivities (D_eff) of bean seeds were determined using Fick's law of diffusion. The values of D_eff were between 1.25 × 10^?9 and 3.58 × 10^?9 m²/s. Activation energy was estimated by an Arrhenius-type equation and was determined as 24.62, 21.06, and 20.36 kJ/mol for citric acid, blanch, and control samples, respectively.     

Convective Drying Kinetics of Red Chillies

The drying kinetics of four varieties of chillies (Pb-Lal, Pb-Guchhedar, Pb-Surkh, and CH-1) was studied. The chillies (pricked and unpricked) were pretreated in the dip sol solution. The treated chillies were dried in an automatic weighing experimental dryer at selected temperatures (45°, 50°, 55°, 60°, and 65°C). The results indicated that drying took place in the falling rate period. Out of three models considered, Page's model was found to be the most suitable for describing the drying behavior of chillies. The dependence of drying constant on temperature was analyzed using an Arrhenius equation. The variety Pb-Lal has the maximum value of activation energy (42.59 kJ/mol), which is also reflected in the reduced drying time for this variety. The results of quality studies of dried chillies in terms of capsaicin content and coloring matter indicated that the Pb-Lal variety had acceptable capsaicin content of 532.08 µg and coloring matter of 73.8 ASTA.     

Drying Kinetics of Tomato Slices in Vacuum Assisted Solar and Open Sun Drying Methods

A lab model vacuum-assisted solar dryer was developed to study the drying kinetics of tomato slices (4, 6, and 8 mm thicknesses) compared with open sun drying under the weather conditions of Montreal, Canada. The drying study showed that the time taken for drying of tomato slices of 4, 6, and 8 mm thicknesses from the initial moisture content of 94.0% to the final moisture content of around 11.5 ± 0.5% (w.b.) was 360, 480, and 600 min in vacuum-assisted solar dryer and 450, 600, and 750 min in open sun drying, respectively. During drying, it was observed that the temperature inside the vacuum chamber was increased to 48°C when the maximum ambient temperature was only 30°C. The quality of tomato slices dried under vacuum-assisted solar dryer was of superior quality in terms of color retention and rehydration ratio. The drying kinetics using thin-layer drying models and the influence of weather parameters such as ambient air temperature, relative humidity, solar insolation, and wind velocity on drying of tomato slices were evaluated.     

Drying of Seabuckthorn (Hippophae rhamnoides L.) Berry: Impact of Dehydration Methods on Kinetics and Quality

Convective hot air drying and freeze drying were investigated as potential dehydration processes to obtain powders of seabuckthorn fruit pulp. Halved seabuckthorn fruits were placed in a hot air dryer and dried at 1 m/s and at 50 or 60°C or freeze dried at less than 30 mTorr and at 20 or 50°C shelf plate temperature. An initial characterization of the seabuckthorn pulp (moisture, pH, soluble solid content, vitamins C and E, total phenolics, and carotenoids) was performed. Water loss, total phenolic compounds, total carotenoids, and vitamin C were determined at different processing times. Vitamin E was determined before and at the end of drying.

Freeze-drying kinetics were faster than air drying, probably due to lower moisture diffusion in the compact, sugary, and oily structure of the air-dried tissue. The temperature had an important impact on hot air–drying and freeze-drying kinetics. Drying method and processing times affected the remaining phenolic, carotenoid, and vitamin contents of seabuckthorn berries. Freeze drying was revealed as a superior method to obtain seabuckthorn powders because of the lower residual moisture content, the ease of grinding, as well as the better nutritional retention.     

Drying kinetics and evolution of the sample's core temperature and moisture distribution of yam slices (Dioscorea alata L.) during convective hot-air drying

In the present work, the drying kinetics and evolution of sample's core temperature and moisture distribution of yam slices during convective hot-air-drying were investigated. In terms of drying kinetics, the effect of drying temperature (50, 55, 60, 65, 70°C), relative humidity (20, 30, 40, 50%), and sample thickness (5, 7, 9 mm) on drying characteristics of yam slices were studied. Results indicated that all the three factors had significant influence on the drying kinetics, whereas drying temperature gave the most significant effect, followed by relative humidity and sample thickness. Moisture-effective diffusivity and activation energy were calculated, and it was found that the diffusivity was in the range of 5.5454 × 10^?10–1.0804 × 10^?9 m²/s and the activation energy was 29.528 kJ/mol. Heat and mass transfer models were developed based on the finite element method to calculate the core temperature and moisture distribution of yam slices during drying. Model validation exhibited good agreement between predicted and experimental data, which illustrated that the developed models could precisely predict the core temperature profile and moisture distribution of the sample. The current work provides further insights to understand the characteristics and mechanism of drying process of yam slices.     

Kinetics of Curing and Thermal Degradation of POSS Epoxy Resin/DDS System

Polyhedral oligomeric silsesquioxanes epoxy resin (POSSER) was prepared from 3-glycidypropyl-trimethoxysilane (GTMS) and tetramethylammonium hydroxide (TMAH) by hydrolytic condensation. POSSER was characterized using Fourier-transformed infrared spectroscopy (FTIR), ¹H-NMR, and liquid chromagraphy/mass spectrometry (LC/MS). The epoxy value of POSSER is 0.50 mol/100 g. The LC/MS analysis indicated that T₁₀ is the majority and contain some amount of T₈, besides, a trace T₉ also exists. The curing kinetics of POSSER with 4,4′-diaminodipheny sulfone (DDS) as a curing agent was investigated by means of differential scanning calorimetry (DSC). The curing reaction order n is 0.8841 and the activation energy Ea is 61.06 kJ/mol from dynamic DSC analysis. Thermal stability and kinetics of thermal degradation were also studied by thermal gravimetric analysis (TGA). TGA results indicated that the temperature of POSSE/DDS system 5% weight loss is approximately 377.0°C, which is higher by 12.6°C than that of pure POSSER, and the primary degradation reaction (300–465°C) followed first order kinetics; the activation energy of degradation reaction is 75.81 kJ/mol.     

Drying Kinetics and Physicochemical Characteristics of Laboratory-Prepared Corn/Wheat Distillers Grains and Solubles Dried with Superheated Steam and Hot Air

The effect of superheated steam (SS) drying and hot air (HA) drying on drying kinetics and changes in the color, crude protein, and amino acid concentrations (in particular, lysine content) of corn/wheat wet distillers grains (WDG) and centrifuged solubles (CS) was evaluated. An inversion temperature was reached at 139°C for WDG and 132°C for CS, above which moisture evaporation rate and qualitative changes under SS drying conditions exceeded the values noted in HA, and below which the reverse was observed. A significant decrease (from 8 to 50%) in the lysine content of WDG and CS was reported during SS and HA. The overall changes in the color (ΔE*) of corn/wheat WDG and CS ranged from 7.9 ± 2.6 to 27.2 ± 1.9 during SS drying and from 11.9 ± 3.7 to 32.0 ± 0.5 during HA drying. The observed deterioration in color was attributed mainly to changes in lightness (L*) and yellowness (b*) of dried samples. The values of L* and b* were reliable predictors of the lysine content of corn/wheat distillers co-products.     

Optimization of explosion puffing drying for high-value yellow-fleshed peach crisps using response surface methodology

Response surface methodology (RSM) was used to comprehensively evaluate the pilot scale nonfried explosion puffing drying (EPD) conditions for developing high-value yellow-fleshed peach crisps. The independent variables were different levels of vacuum drying temperature, vacuum drying time, and puffing pressure difference. The responses were crispness, total color difference (ΔE), total carotenoid content (TC), and DPPH radical scavenging capability (AEAC). Statistical analysis revealed that vacuum drying temperature significantly affected all the responses, puffing pressure difference showed maximum influences on TC, AEAC, and crispness, while vacuum drying time showed influences on TC and AEAC. The optimum EPD conditions obtained by RSM were vacuum drying temperature, vacuum drying time, and puffing pressure difference of 73?°C, 144?min, and 0.05?MPa, respectively. At this optimal condition, crispness, ΔE, TC, and AEAC value were found to be 7.3?N, 18.3, 53.5?µg/mg d.w., and 865.4?mg AA/100g, respectively. The EPD-dried yellow-fleshed peach crisps contained higher amounts of carotenoids and AEAC values when compared to hot-air dried samples, they were also found to be crispier than vacuum freeze-dried samples.     

Drying kinetics and effect of air-drying temperature on chemical composition of Phyllanthus amarus and Phyllanthus niruri

In this study, the drying kinetics of Phyllanthus amarus and Phyllanthus niruri were investigated experimentally in an air-drying oven as a function of drying temperature (50, 60, and 70°C). The effects of the air-drying temperature on the phenolic content and the LC–MS profile were also studied. Increases in air-drying temperature reduced the drying time and increased the effective moisture diffusivity. An Arrhenius relationship with activation energy values of 22.828 and 43.129?kJ/mol for P. niruri and P.amarus, respectively, expressed the effect of temperature on the diffusivity. Air drying at 70°C increased the availability of some phenolic compounds. However, the higher temperature negatively affected some sensitive components.     

The Role of Processing Conditions on the Color and Antioxidant Retention of Jet Tube Fluidized Bed–Dried Blueberries

Jet tube fluidized bed drying was investigated as a means of rapidly generating shelf-stable and high-quality sweetened and nonsweetened blueberries. Sugar-infused and noninfused scarified Rabbiteye blueberries (Vaccinium ashei ‘Brightwell’) were dried at 99, 107, and 116°C. Prior scarification of the blueberry surface aided in decreasing the drying time. Increased lightness (L*) values were most notable at higher drying temperatures for sugar-infused blueberries, suggesting loss of pigments. Total monomeric anthocyanins level, initially 7.65 mg cyanidin-3-O-glucoside equivalents (C3G eq)/g extract, decreased as drying temperature increased and ranged between 4.07 down to 1.51 mg C3G eq/g extract for dried blueberries. The total phenolics content increased with drying for noninfused blueberries, with highest levels of 31.6 mg gallic acid equivalents (GAE)/g extract for samples dried at 107°C. With the exception of sugar-infused berries dried at 107 and 116°C, the dried blueberries maintained or demonstrated slightly increased hydrophilic oxygen radical absorbance capacity (H-ORAC_FL) values, indicating that their antioxidant capacity was retained upon drying. Blueberries dried at 107°C possessed the greatest preference scores and best retention of blueberry flavor and required a relatively short drying time.     

Performance of different process additives on the properties of mango powder obtained by drum drying

The use of process additives was evaluated in the drum drying of commercial mango pulp, using corn starch, maltodextrin 10/20 DE, and glyceryl monostearate (GMS). The mass flow rate (MFR) and some powder properties were analyzed: moisture content, vitamin C, total phenolic compounds, carotenoids, β-carotene, glass transition temperature (T_g), hygroscopicity, solubility, color, rheological behavior and color of reconstituted pulp. The pulps presented non-Newtonian and pseudoplastic fluid behavior, while T_g values ranged from 29°C to 38°C. The process performed with 3% corn starch and 0.5% GMS (dry basis) resulted in greater MFR (8.0?±?0.2?kg/h?m²) and vitamin C retention (61.0?±?0.7%).     

Drying Kinetics of Biofilms Obtained from Chestnut Starch and Carrageenan with and without Glycerol

Drying kinetics of biofilms from chestnut starch and hybrid carrageenan were experimentally determined and modelled. The biofilms were obtained by mixing the respective solutions (4.0% w/w) of both substances in the proportion 80/20 of chestnut starch/hybrid carrageenan. Glycerol (at 5.0% w/w) was added to some biofilms. Biofilms were prepared using a casting method. Drying kinetics were performed at 30, 40, and 50°C for forced air convection (1.8 ± 0.1 m/s) and 30 and 50°C for natural convection. Constant drying rate period, above critical moisture content (5.4 and 4.2 kg water/kg d.b. without and with glycerol, respectively) allowed the evaluation of the heat transfer coefficients. The water diffusion coefficients were determined in the falling rate period assuming a semi-infinite slab with variable thickness. Water sorption isotherms of biofilms at 25°C were determined and fitted with the GAB model. Mechanical properties of different biofilms showed no significant differences for Young's modulus values (44.0 ± 4.6 MPa). Nevertheless, films prepared at 30°C under natural drying showed the lowest values of tensile strength and elongation (32.2 ± 4.9 MPa and 0.85 ± 0.11%).     

Accurate Determination of Moisture Content of Organic Soils Using the Oven Drying Method

Abstract

The accuracy of moisture content values determined for organic soil using the oven drying method is dependent on the oven drying temperature. Some charring of the organic fraction occurs at the standard oven drying temperature of 110 ± 5°C; pore water remains in the soil when temperatures below 100°C are used. A new technique to determine the specific oven drying temperature that yields the correct value of the moisture content for organic soils is presented. Routine moisture content tests should be conducted at the standard oven drying temperature; moisture content values determined on the basis of the recommended oven drying temperature of 60°C include a larger error. A moisture content parameter is introduced to facilitate direct comparison of moisture content values calculated on the basis of different oven drying temperatures.     

Forced Convective Drying of Wastewater Sludge with the Presentation of Exergy Analysis of the Dryer

The main objective is studying the fundamental aspect, by means of drying kinetics and the application of forced convective drying of wastewater sludge with the determination of the optimum drying conditions. The drying system is composed of two units; small samples of 2.5 g are dried in the first unit and a bed of sludge weighing 250 g is dried in the second unit. The experiments are performed under air temperatures varying between 80°C and 200°C. The range of the air velocity and its humidity is 1–2 m/s and 0.005–0.05 kg_water/kg_{dry air}, respectively. The experiments are performed for two different sludges: activated sludge (AS) and thermalized and digested sludge (TDS). Usually, three main drying phases are observed during drying of bed of sludge. These phases are reduced to only two for small samples. Determination of the influent parameters shows that the temperature of the drying air and sludge origin can profoundly influence the drying kinetic of the sludge. The exergy analysis of the two units of the drying system allows selecting 140°C, 2 m/s, and 0.05 kg_water/kg_{dry air} as optimum drying conditions with an exergy efficiency reaching 90%.