Moisture diffusivity and drying kinetic equation of convective drying of grapes

The Desalting Process for Table Olives and Its Effect on Their Physicochemical Characteristics and Nutrient Mineral Content

The desalting process is critical for packaging table olives in brine with reduced NaCl or fortified mineral nutrients. In this study, the effect of desalting on the physicochemical characteristics and mineral content of green Manzanilla Spanish-style (plain and stuffed with pepper paste) and DOP Aloreña de Málaga table olives was investigated for the first time. The surface colour of the fruits turned slightly brownish, and the olives became somewhat softer. The lactic acid, the mineral macronutrients (mainly) and micronutrient contents decreased, while flesh moisture increased. The kinetic parameters of the minerals' losses depended on the presentation, with the estimated values for plain olives being the lowest (slowest desalting). Overall, the desalting process resulted in slight quality damage and a moderated decrease in the mineral concentration in the flesh, leading to some product degradation. This study provides quantitative information on these changes that may affect the commercial value of the final products and offers information for viable designs.

Evaluation of processing mechanism in Astragali Radix by low-field nuclear magnetic resonance and magnetic resonance imaging

Astragali Radix (Huangqi) is an important herb medicine that is always processed into pieces for clinical use. Many operations need to be performed before use, among which drying of Astragali Radix (AR) pieces is a key step. Unfortunately, research on its drying mechanism is still limited. Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) techniques were applied to study the moisture state and distribution during drying. The content of bioactive components and texture changes were measured by HPLC and texture analyzer, respectively. The moisture content of the AR pieces decreased significantly during drying, and the time to reach the drying equilibrium were different at different temperatures. The time when at 70°C, 80°C, and 90°C reach complete drying are 180 min, 150 min and 120 min, respectively. 80°C was determined as the optimum drying temperature, and it was observed that the four flavonoids and astragaloside IV have some thermal stability in AR pieces. When dried at 80°C, although the total water content decreased, the free water content decreased from 99.38% to 15.49%, in contrast to the increase in bound water content from 0.62% to 84.51%. The texture parameters such as hardness changed to some extent, with the hardness rising most significantly from 686.23 g to 2656.67 g. Correlation analysis revealed some connection between moisture content and LF-NMR and texture analyzer parameters, but the springiness did not show a clear correlation with most parameters. This study shows that HPLC, LF-NMR, MRI, and texture analyzers provide a scientific basis for elucidating the drying principles of AR pieces. The method is useful and shows potential for extension and application; therefore, it can be easily extended to other natural herb medicines.

Computational Modeling of Fluidized Beds with a Focus on Pharmaceutical Applications: A Review

The fluidized bed is an essential and standard equipment in the field of process development. It has a wide application in various areas and has been extensively studied. This review paper aims to discuss computational modeling of a fluidized bed with a focus on pharmaceutical applications. Eulerian, Lagrangian, and combined Eulerian-Lagrangian models have been studied for fluid bed applications with the rise of modeling capabilities. Such models assist in optimizing the process parameters and expedite the process development cycle. This paper discusses the background of modeling and then summarizes research papers relevant to pharmaceutical unit operations.

Influence of Different Dehydration Levels on Volatile Profiles, Phenolic Contents and Skin Hardness of Alkaline Pre-Treated Grapes cv Muscat of Alexandria (Vitis vinifera L.)

A dehydration experiment was carried out on Vitis vinifera L. cv Muscat of Alexandria (synonym Zibibbo) following the process for the production of renowned special dessert wines produced on Pantelleria island (Sicily, Italy). Harvested berries were pre-treated in a sodium hydroxide dipping solution (45 g/L, dipped for 185 s, 25 °C) to accelerate the drying process, rinsed, and dehydrated in simulated conditions (relative humidity 30%, 30 °C temperature, air speed 0.9 m/s). Three dehydration levels were achieved, corresponding to “Passolata”, “Bionda”, and “Malaga” stages (35%, 50%, and 65% of weight loss, respectively) of the Pantelleria denomination of origin (DOC). Grape skin mechanical properties, technological parameters, phenolics, and aroma profile varied considerably during dehydration. The most important aroma compounds for their olfactory impact, such as linalool, geraniol, nerol, and citronellol, especially in glycosylated forms, significantly increased in dried grapes compared to fresh ones, even if aroma profile modification occurred. A decrease in break skin force could have induced higher release of flavonoids. The findings showed relevant changes, allowing winemakers to better select the ratio of fresh and dehydrated grapes in the function of the final desired wine.

Kinetic Studies and Moisture Diffusivity During Cocoa Bean Roasting

Cocoa bean roasting allows for reactions to occur between the characteristic aroma and taste precursors that are involved in the sensory perception of chocolate and cocoa by-products. This work evaluates the moisture kinetics of cocoa beans during the roasting process by applying empirical and semi-empirical exponential models. Four roasting temperatures (100, 140, 180, and 220 °C) were used in a cylindrically designed toaster. Three reaction kinetics were tested (pseudo zero order, pseudo first order, and second order), along with 10 exponential models (Newton, Page, Henderson and Pabis, Logarithmic, Two-Term, Midilli, Verma, Diffusion Approximation, Silva, and Peleg). The Fick equation was applied to estimate the diffusion coefficients. The dependence on the activation energy for the moisture diffusion process was described by the Arrhenius equation. The kinetic parameters and exponential models were estimated by non-linear regression. The models with better reproducibility were the pseudo first order, the Page, and the Verma models (R2 ≥ 0.98). The diffusion coefficients that were calculated were in the order of 1.26 to 5.70 × 109 m s−2 and the energy activation for moisture diffusion obtained was 19.52 kJ mol−1.

Novel Ingredients Based on Grapefruit Freeze-Dried Formulations: Nutritional and Bioactive Value

Grapefruit is a fruit with interesting nutritional value and functional properties, but a short life. Freeze-drying (FD) is a valuable technique as it produces high-quality dehydrated products. This study is aimed to obtain new food ingredients based on freeze-dried grapefruit formulated with high molecular weight solutes (gum arabic and bamboo fiber) in three different proportions (F1, F2, and F3). To improve the FD, a mild microwave drying pre-treatment was applied. Influence of the water content and the presence of high molecular weight solutes on freeze-drying kinetics was tested by Midilli-Kucuk and Page models. The best FD kinetic model fit on grapefruit powders were Midilli-Kucuk for F2 and F3, and Page for F1, and the adequate freeze-drying times for F1, F2, and F3 were 24, 16, and 18 h, respectively. Final samples were evaluated for nutritional and antioxidant capacity. Gum arabic and bamboo fiber present a protector effect, which results in a significant antioxidant capacity due to the protection of flavonoids and antioxidant vitamins. These novel food ingredients could be of great interest for the food industry in order to develop foods with improved antioxidant capacity as well as enriched in natural fibers and/or micronutrients.

Convective drying of onion: modeling of drying kinetics parameters

Drying is a simultaneous heat and mass transfer processes. Drying kinetics is determined by both internal properties and external drying conditions. In this study, two important drying kinetics parameters of onions i.e. effective water diffusivity and relative activation energy of reaction engineering approach (REA) are determined. The generated parameters are used to model thin layer drying of onion at different temperatures (40, 50, 60, and 70 °C) and relative humidity of 20%. The effective water diffusivity is in the range of 2.8 × 10^-10 m² s^-1 and 8.1 × 10^-10 m² s^-1. Unlike the diffusivity, the relative activation energy of the REA is independent on drying conditions and thus the latter approach requires less effort in generating the transport properties. The transport parameters can be applied for assisting in designing dryer units and evaluating the performance of existing dryer units.

Experimental data on convective drying of potato samples with different thickness

A laboratory setup is developed to examine the characteristics of convective drying of a moist potato sample. The thickness effect (5, 10 and 15 mm) of product on heat and mass transfer during potato drying was presented. Potato samples were dried at temperature of 51 °C and air velocity of 1 m s⁻¹. Structural Change (length, width and thickness) of the samples were measured during drying. The heat distribution at different locations, sides surfaces and heart of the samples, was acquired at a time interval of 30 min for the test period. According to drying rate, potato drying is predominantly in the falling rate period. The moisture diffusivity data determined from experimental convective drying kinetics. The method based on the analytical solution of a fickian diffusive model has been developed to both evaluate the sample thickness effects on moisture diffusivity. Moreover, this dataset is made public in order to be used by other researchers studying the performances analysis of the drying systems.

Moisture Diffusivity of Seedless Grape undergoing convective drying

Seedless grape (Sultana grape) is a very important commercial fruit grown in large quantities in Tunisia. This product is characterized by a high initial moisture content (the initial wet basis moisture content of the fruit is more than 80 %), and thus a high shrinkage during drying. The mature seedless grape is a spherically shaped fruit. Thermo-physical properties and drying kinetics of seedless grape is essential for the optimization of its drying processes. This paper is composed of two parts, the first one is reserved to the experimental study of seedless grapes, such as the establishment of the desorption isotherms which were determined at 40, 50, 60 and 70 °C by using static gravimetric method and these desorption data were fitted by GAB model. Then we were interested in measurement of the axial hydrous shrinkage of a grape berry and it was expressed as a function of moisture content. Indeed, the drying kinetics under different controlled conditions of air temperature and relative humidity were realized. In the second part, the moisture diffusivity of the seedless grape was determined by minimizing the sum of square of deviations between the predicted and experimental values of moisture content of convective drying kinetics. The adopted approach was based on a numerical solving of the conservation equation of the solid phase and the equation of diffusion/convection of liquid phase for spherical geometry, coupled by the solid phase velocity due to shrinkage. The moisture diffusivity of seedless grape increased with temperature and was correlated by an Arrhenius-type equation. Indeed, the effect of moisture diffusivity was expressed by an exponential function. The moisture diffusivity of seedless grape ranged between 3.5610−10 (m2/s) and 12.610−10 (m2/s). Activation energy was found equal to 57.76 kJ/mol.

Effect of Blanching and Air Flow Rate on Turmeric Drying

Turmeric processing involves two main steps, blanching and drying. Blanching is a common step in the traditional processing of rhizomes, and hot air drying is an alternative to traditional solar drying. For this study, drying kinetics were performed at different air flow rates (0.2, 0.5, 0.7, 1.2, 2.1, 2.6, 3 and 4m/s) to determine the effect of air flow on the process. To examine the blanching effect, drying kinetics were carried out with blanched and unblanched rhizomes at different temperatures (60, 70, 80, 90 and 100ºC). A diffusion model and two empirical models (Weibull and Peleg) were used to describe mass transfer during drying. The effect of air flow rate on external resistance was observed, and the air velocity transition zone between the external and internal resistance control zone was identified (1–2m/s). Blanching previous to drying increased the process rate at all the temperatures tested, although its effect was reduced when the air drying temperature increased. Empirical models fitted better drying kinetics than the diffusion model, however, the diffusion model provides valuable information about the phenomenon of water removal and scaling up.

Mass Transfer During Osmotic Dehydration of Pineapple

The diffusion coefficients of water and solutes are important parameters in the analysis, design and optimisation of an osmotic dehydration process. This work estimated by Fick’s Law the diffusion coefficients of water and sucrose during the osmotic dehydration of slices of pineapple fruit in sucrose solution at different temperatures. In addition, it analysed the effect of the change in thickness (shrinkage) during the process, and the use of higher order terms in the analytical solution. The model results were in good agreement with experimental data of water loss and solid gain. The best fit was found when the shrinkage was considered in a simple model based on the solution of Fick’s Law. The equilibrium water content ranged between 34 and 36% for a 60% w/w sucrose solution and was practically independent of temperature. Equilibrium sugar content increased from 45 to 54% as the temperature rose from 30 to 50°C. Thickness variation was found to be independent of temperature and was only dependent on water content.