Mass Transfer Modeling During Osmotic Dehydration of Hexahedral Pineapple Slices in Limited Volume Solutions

The study of mass transfer during osmotic dehydration process in limited volume solutions was carried out to evaluate the diffusion coefficients of sucrose and water in the osmotic treatment of hexahedral pineapple slices. The experimental osmotic dehydration kinetics for pineapple slices of two different sizes were conducted at 25 °C using a 1:1 solution to fruit weight ratio. The analytical solution of a 3D mass transfer model considering a limited volume of osmotic solution (i.e., an osmotic media of variable solute concentration) was used for describing the mass transfer in osmotic dehydration of pineapple slices. This model was fitted to the experimental kinetics by means of nonlinear regression to obtain the diffusion coefficients. Additionally, the diffusion coefficients were evaluated considering an infinite volume of osmotic solution (i.e., an osmotic media of constant solute concentration). Results showed that the proposed model may be fitted accurately to the experimental osmotic dehydration kinetics and allows the estimation of diffusion coefficients when solute concentration in the osmotic media varies along the process.     

The Effect of Path Diffusion on The Effective Moisture Diffuslvlty in Carrot Slabs

ABSTRACT

In order to evaluate the effect of path diffusion on the average moisture diffusivity in carrot. drying curves for different shaves (slices and cylinders) and temperatures of 50, 60 and 70°C were ohtained takine into consideration the use of an average leneth of carrot sample (slice thickness or the cylinder radio). The. results showed significant differences betuecn radial and axial average diffusivities. Significant differences were also observed between core and annular diffusivity. The experimenta1 drying curves did not show enough evidence on the effect of drying temperature on the average moisture diffusivity.     

GC–MS and GC–olfactometry analysis of aroma compounds in a representative organic aroma extract from cured vanilla (Vanilla planifolia G. Jackson) beans

Volatile compounds from cured vanilla beans were extracted using organic solvents. Sensory analysis showed that the aromatic extract obtained with a pentane/ether (1/1 v/v) solvent mixture provided the extract most representative of vanilla bean flavour. Sixty-five volatiles were identified in a pentane/ether extract by GC–MS analysis. Aromatic acids, aliphatic acids and phenolic compounds were the major volatiles. By GC–O analysis of the pentane/ether extract, 26 odour-active compounds were detected. The compounds guaiacol, 4-methylguaiacol, acetovanillone and vanillyl alcohol, found at much lower concentrations in vanilla beans than vanillin, proved to be as intense as vanillin.     

Characterization of La2−xSrxCoTiO6 (0.6 ≤ x ≤ 1.0) series as new cathodes of solid oxide fuel cells

La_2−xSr_xCoTiO₆ (0.6 ≤ x ≤ 1.0) compound series is prepared by Sr-substitution in the A-site of the perovskite by a modified Pechini procedure under air. Charge compensation as Sr²⁺ content increase occurs by Co²⁺ oxidation to Co³⁺. Reduced samples are obtained by further treatment under 5%H₂/Ar and characterized by Neutron Powder Diffraction. Upon redution, Co³⁺ to Co²⁺ reduction and oxygen vacancies creation are detected. Dependence of total conductivity with temperature and pO₂ exhibits a typical p-type semiconducting behaviour. Results show that the higher the Sr content, the higher holes (Co³⁺) concentration and consequently, La_2−xSr_xCoTiO₆ (x = 1.0) shows the highest conductivity (13.23 S/cm at 1073 K in air). The negligible reactivity with YSZ, used as the electrolyte, of symmetrical cells under oxidant conditions and the moderate thermal expansion found by XRD point to their possible use as SOFC cathodes. Thus, La_1.2Sr_0.8CoTiO₆-based cathodes display polarization resistance of 0.9 Ω cm² at 1073 K in oxygen, only slightly above than the current state-of-the-art.     

The Effect of Path Diffusion on The Effective Moisture Diffuslvlty in Carrot Slabs

In order to evaluate the effect of path diffusion on the average moisture diffusivity in carrot. drying curves for different shaves (slices and cylinders) and temperatures of 50, 60 and 70°C were ohtained takine into consideration the use of an average leneth of carrot sample (slice thickness or the cylinder radio). The. results showed significant differences betuecn radial and axial average diffusivities. Significant differences were also observed between core and annular diffusivity. The experimenta1 drying curves did not show enough evidence on the effect of drying temperature on the average moisture diffusivity.     

Effect of Process Variables on Spray-Dried Garlic Juice Quality Evaluated by Multivariate Statistic

Garlic juice was spray-dried at different inlet-outlet (110, 130 °C)–(60, 70, 80 °C) air temperatures and different types (gum arabic, DE-10 maltodextrins) and concentrations (0, 0.5, 0.8 g/g dm) of carrier material. Dried product quality was evaluated through moisture, water activity, powder color coordinates, and the retention of allicin and pyruvic acid. A complete 2?×?3?×?3 experimental design was developed but some treatments were experimentally nonfeasible. Then, results were analyzed by 1WANOVA and PCA. Drying conditions that maximized allicin retention were maltodextrin at 110 °C, 70 °C of inlet, outlet air temperatures, and 0.5 g carrier/g dm. Under these conditions, retentions were as follows: 76.9 % allicin and 89.9 % pyruvic acid. These results suggest that the obtained powder might be useful as a food additive or ingredient due to the higher retention levels of pyruvic acid than other types of convective drying.     

Food Sorption Isotherms Prediction Using the Ross Equation

Estimation of food sorption isotherms was developed using Ross, Raoult, Norrish and Henderson equations. Food average composition of main solutes (sucrose, glucose, fructose, xylose, maltose, lactose, and salts), nonsolutes (starch, protein, and fiber), and the solute solubility at different temperatures were taken into account. The individual water activity of a single solute was kept constant at moisture contents below saturation at given temperature. Water activities for non-solutes were evaluated with Henderson equation based on literature data for starch, protein and fiber. Sorption isotherms for apricot, raisins, potato, rice, bean and nonfat milk were predicted and compared with those reported in literature. Predicted isotherms represented an expected behavior of the experimental isotherms obtained by different authors.     

Extraction kinetics modeling of antioxidants from grape stalk (Vitis vinifera var. Bobal): Influence of drying conditions

The use of antioxidant extracts obtained from natural products is highly relevant in the food, chemical and pharmaceutical industry. The mathematical analysis of the antioxidant extraction could contribute to a better understanding of the process and is fundamental for optimization tasks. However, the high complexity of natural matrixes makes modeling difficult. The main aim of this work was to model the antioxidant extraction process from grape stalk in order to quantify the influence of the previous drying operation on extraction kinetics. The antioxidant extraction kinetics for freeze dried and hot air dried samples at several temperatures (40, 55, 70, 85, 100 and 115 °C) were carried out, using the FRAP method to measure the antioxidant capacity in the extracts. A diffusion model was developed that took significant external resistance as well as the complex geometry of grape stalk into consideration. From the modeling results, the influence of the drying conditions on the antioxidant concentration of the dry stalk, the antioxidant effective diffusivity and the mass transfer coefficient were identified.