Strawberry drying: Development of a closed-cycle modified atmosphere drying system for food products and the performance evaluation of a case study

In the present study, a closed-cycle modified atmosphere drying (CC-MAD) system was developed as an alternative drying technique to facilitate drying processes for agricultural commodities appropriate to highly humid and sunny regions with a better quality. An absorption dehumidifying system was designed for working pseudo-continuously with the most efficient absorbent in terms of moisture absorption, desorption rate, and capacity. The system, assisted by a solar panel for absorbent regeneration, was tested, while its optimum working condition was determined by strawberry drying. This unique process was comparatively carried out using hot-air and freeze-drying techniques in terms of processing time and final product quality. Strawberry slices (5?mm thickness) were dried successfully using CC-MAD. The optimum drying conditions of CC-MAD were determined as drying temperature of 60°C, drying air/gas velocity of 3?m/s and drying medium oxygen level of 9.47%. The loss of ascorbic acid was significantly reduced by CC-MAD technique. These losses were found to be 2.9, 6.9, 27.2, and 23.8% by freeze-drying, CC-MAD, hot-air drying, and hot-air drying combined with CC-MAD, respectively. The total monomeric anthocyanins loss was also significantly reduced by the CC-MAD technique (20.3%), in a similar way to that of freeze-drying (18.1%) in comparison with hot-air drying (40.4%). In addition, CC-MAD (12,446?kJ/kg fresh product at 4?h drying time) is three times more advantageous in terms of energy cost compared with freeze-drying (30492.8?kJ/kg fresh product at 24?h drying time) and six times faster in terms of drying time. This new drying system can be used as an alternative to freeze-drying in the drying of foods, especially in products sensitive to oxidation.     

A simplified correlation for fixed bed pressure drop

An experimental study was conducted on the pressure drop characteristics of a variety of vertical packed beds in turbulent flow of air. The materials of different particle diameter, D_p, with a range of sphericity Φ, 0.55 ≤ Φ ≤ 1.00 were used in random loose packing to produce beds of different lengths, L, with a range of porosity, ε, 0.36 ≤ ε ≤ 0.56. In the covered test cases the cross-sectional velocity distribution at the exit plane of the packed beds and the pressure drop ΔP_Bed were measured in a particle Reynolds number range of Re_p, 675 ≤ Re_p ≤ 7772. The particular emphasis of the study was given to determine the influence of ε, Φ, D_p, L, Re_p on ΔP_Bed. In this respect the measurements of ΔP_Bed were compared with the well-known Ergun's Equation and the data were expressed in terms of correlations through introduced dimensionless parameters of pressure coefficient, ΔP^? and exit Reynolds number Re_exit. The proposed correlations of ΔP^? = ΔP^?(εRe_pD_p / L) and Re_exit = Re_exit(Re_pD_p / L) are found to be appropriate for the determination of ΔP_Bed and mean exit velocity, U, respectively with an acceptable fit of experimental data in an error margin less than ± 20%. The methodology is presented in this paper as an alternative approach to the available literature on packed beds.     

A generalized reference state extends the applicability of approximative kinetics in metabolic engineering

BACKGROUND: The use of approximative kinetics for modeling enzyme kinetics and for metabolic engineering purposes has become increasingly attractive. Despite a list of advantages, the proposed use of a steady state for reference limits the use of such kinetic formats. RESULTS: Here, to avoid these limitations, an alternative formulation is proposed for the linlog approximative kinetics introducing ‘a characteristic set’ for normalization. The necessary equations for the parameter (elasticities and the reaction rate of the characteristic set) estimation framework using data obtained from various types of perturbation experiments are given. The use of the new formulation is exemplified with three illustrative examples: parameter estimation in steady state and in dynamic experiments; and prediction of the effect of a mutation in enzyme kinetics properties. The implications of the new formulation are discussed. CONCLUSIONS: By introducing a so‐called characteristic set, we show that the approximative quality of this kinetics is improved and this formulation can be used to analyze and model data from a broader set of experimental scenarios. Copyright © 2012 Society of Chemical Industry     

Immunohistochemical distribution of heat shock protein 70 and proliferating cell nuclear antigen in mouse placenta at different gestational stages

The aim of the present study was to investigate immunohistochemical distribution of heat shock protein 70 (Hsp70) and proliferating cell nuclear antigen (PCNA) in the mouse placenta at different gestational stages. For this purpose a total of 18 Swiss albino female mice at 12–14 weeks of age were used. Females were sacrificed on days 3 (early), 10 (mid‐), and 17 (late) of pregnancy and the implantation sites of the pregnant uterus were sampled. The sections were made transversely through the central region of the implantation site and stained with hematoxylin and eosin for histological examination. PCNA and Hsp70 was stained immunohistochemically. Since the definitive placenta was not still formed on day 3 of pregnancy, Hsp70 and PCNA positivity were evaluated in only luminal epithelium and decidual‐stromal cells. On days 10 and 17 of pregnancy, Hsp70 and PCNA positivity were evaluated in labyrinth zone, junctional zone and decidual layer of placenta. Hsp70 expression was observed trophoblast cells and decidual cells and was relatively constant throughout the pregnancy. This protein was strongly labeled in the trophoblast cells; while decidual cells were displayed moderate staining. In early pregnant mouse uteri, PCNA was mainly localized in decidual‐stromal cells. The trophoblast cells and decidual cells displayed highly proliferative activity at the midgestational period. However there was a significant decrease in the percentage of PCNA positive cells in late gestation. Microsc. Res. Tech. 79:251–257, 2016. © 2016 Wiley Periodicals, Inc.     

Imidazole modified acrylate-containing photocured hydrogels for the efficient removal of malachite green dye from aqueous solutions

In this work, we aimed to prepare a simple and an efficient adsorbent for the removal of toxic, cationic dye; malachite green (MG). We reviewed many previous studies and designed our adsorbent based on the rationale that (1) acidic groups containing monomers which are capable of making hydrogen bonds (or electrostatic interactions) with MG are very effective in adsorption and (2) π-π stacking enhances the adsorption capacity. We first synthesized an imidazole-acrylate adduct and used it for the preparation of photocured hydrogels. The imidazole-acrylate adduct was characterized by H NMR and FTIR spectroscopy. The effect of experimental conditions on the MG adsorption properties of the hydrogels such as the effect of pH, time and MG concentration were also investigated. Under the optimum conditions (pH = 6 and 220 min contact time) at room temperature, the maximum adsorption capacity was found as high as 714.28 mg/g. The results showed that the adsorption process of the optimum hydrogel, which can be used 4 times without a significant loss in its adsorption capacity, fits the Langmuir isotherm model. The hydrogel adsorbent displayed good selectivity and reusability.     

Arsenite removal from groundwater in a batch electrocoagulation process: Optimization through response surface methodology

In this study, influences of seven process variables such as initial pH (pH_i), applied current (i), operating time (t_EC), initial As(III) concentration (C_o), diameter of Fe ball anode (d_p), column height in the electrocoagulation (EC) reactor (h) and airflow rate (Q_air) for removal of As(III) from groundwater by a new air-fed fixed-bed EC reactor were evaluated with a response surface methodology (RSM). The proposed quadratic model fitted very well with the experimental data for the responses. The removal efficiencies and operating costs were determined to be 99% and 0.01 $/m³ at the optimum operating conditions (a pH_i of 8.5, 0.05 A, 4.94 min, d_p of 9.24 mm, h of 7.49 cm, Q_air of 9.98 L/min for 50 µg/L). This study clearly showed that the RSM in the EC process was a very suitable method to optimize the operating conditions at the target value of effluent As(III) concentration (10 µg/L) while keeping the operating cost to minimal and maximize the removal efficiency.     

Utilization of lentil flour as a biopolymer source for the development of edible films

Lentils are one of the cheapest and most nutritional protein sources for vegetarians. Our objective in this study was to evaluate the feasibility of using lentil flour as a raw material for the development of edible films and to investigate the effects of the glycerol concentration (C_g = 1%, 1.5%, and 2%) and process temperature (T_p; 70 and 90 °C) on the physical properties of these films. The films were characterized via their density; water solubility; thermal, morphological, and chemical characteristics; water vapor permeability (WVP); and tensile and optical properties. The lentil flour films were highly transparent and had lower water solubility values yet similar WVPs and mechanical properties compared to most other biodegradable films. An increase in C_g led to the formation of more flexible films with increased hydrophilicity. A T_p of 90 °C resulted in yellower, more transparent films with increased stiffness compared to a T_p of 70 °C. In this study, lentil flour was shown to be an ideal source for edible film production. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46356.     

Frequency Selective Characteristics of a Plasma Layer with Sinusoidally Varying Electron Density Profile

In this study reflection, absorbtion and transmission characteristics of a plasma layer having sinusoidally varying electron number density are analysed. In the analysis, plasma layer is divided into thin subslabs with constant electron number densities. The general frequency selective behavior of the plasma is investigated by varying the plasma parameters, external magnetic field excitation and sinusoidal electron distribution in order to be used in recent plasma applications.