Role of Post-Exposure Time in Co(II) Sorption of Higher Concentrations on Electron Irradiated Sheep Wool

Sorption of Co(II) was investigated on natural as well as accelerated electron beam modified sheep wool involving low and high concentrations up to 200 mmol·dm−3. The sorption experiments confirmed the dependence of the sorption capacity not only on sorbate concentration and absorbed dose of energy, but also on post-exposure time. Post-exposure heating to accelerate transformation of the wool structure was of no effect on the sorption comparing with a simple storage for a period of 100 days. Under all tested conditions, the sorption maximum was measured for Co(II) concentration of 125 mmol·dm−3 and that was assigned to form a Co(II) complex with keratin. This assumption was tested on visible spectra of mixed solutions of Arginine and Co(II) to be a simplified model of Co(II) interaction with keratin. The sorption decrease is associated with generation of cross links between macro-chains through ligands of the Co-complex. The nodal points are a hindrance to diffusion of next ions into the fibers. Also, pH variations of aqueous extracts from the wool samples depending on absorbed dose and post-exposure time indicate complexity of the structural transformation being specific for each dose applied.

THERMODINAMIC PARAMETERS ON THE SORPTION OF PHOSPHATE IONS BY MONTMORILLONITE

The sorption of phosphate by montmorillonite at 10, 30, and 50 oC were investigated aiming to mainly determine thermodynamic parameters for the formation of surface complexes in the adsorption of phosphate ions by montmorillonite. Data were collected by adsorption edge experiments investigating the effect of pH, adsorption isotherms enabling the effect of sorbate concentration, and acid-base titration calculating protons released or taken up by adsorption process. Data analysis was carried out using surface complexation model to fit the data collected in this study using the parameters obtained from previous study, as well as to calculate the values of ΔH and ΔS. Previous study reported that phosphate ions formed two outer-sphere surface complexes with active sites of montmorillonite through hydrogen bonding. In the first complex, [(XH)0– H2L─]─, the phosphate was held to permanent-charge X─ sites on the tetrahedral siloxane faces, and the second complex, [[(SO─)(SOH)]– – [H2L]─] 2─ was formed through the interaction between the phosphate and variable charge surface hydroxyl groups at the edges of montmorillonite crystals and on the octahedral alumina faces. The values of ΔH for the first and second reactions are 39.756 and 3.765x10-7 kJ mol‒1 respectively. Since both reactions have positive enthalpy values, it can be concluded that the reactions are endothermic. Large energy for the first reaction is needed by X─ sites (permanent negatively charge sites of montmorillonite) to be partially desolvated, on which K+ or other surface cations are replaced by H+ ions in the surface protonated process, and are then ready to interact phosphate ions in the solution. Small values of ΔH for the second reactions indicates that hydrogen bonds formed by phosphate and SOH sites in the second reaction are easily broken out, and the phosphate can easily desorbed from the surface. The values of ΔS for the first and second reactions are 122.523 and 2.393 x10-2 J K‒1 mol‒1, which are greater than -10 kJ mol‒1 and indicates that the surface reactions occurs through dissociative mechanisms.Keywords: montmorillonite, adsorption edge, extended constant capacitance, surface complexation model, enthalpy, reaction mechanisms

Effect of Acidified Sorbate Solutions on the Lag-Phase Durations and Growth Rates of Listeria monocytogenes on Meat Surfaces†

The surfaces of ready-to-eat meats are susceptible to postprocessing contamination by Listeria monocytogenes. This study quantified the lag-phase durations (LPD) and growth rates (GR) of L. monocytogenes on the surfaces of cooked ham as affected by sorbate solutions of different concentrations and pH levels. Slices of cooked ham inoculated with a four-strain mixture of L. monocytogenes (ca. 103 CFU/g) were surface treated with sorbate solutions of 0 to 4% (wt/vol) at pH 4.0 to 6.5, vacuum packaged, and stored at 4 to 12°C for up to 45 days. The LPD and GR of L. monocytogenes were used to develop response surface models. The models estimated that the LPD of L. monocytogenes in samples treated with solutions of pH 4.0 to 5.5 (no sorbate) were 0 to 11 days and the GR were 0.25 to 0.36 log CFU/day, respectively, at 4°C. With the treatments of 2 and 4% (wt/vol) sorbate solutions, the LPD were estimated to be extended to 2 to 26 days and 34 to >45 days, and the GR were reduced to 0.15 to 0.30 and 0 to 0.19 log CFU/day, respectively. At 4°C, increasing sorbate concentrations by 1% (wt/vol) to 2, 3, and 4% (wt/vol) at pH 5.5 to 4.0 led to an extension of LPD by 2 to 11, 10 to 19, and 18 to 27 days, whereas the GR were reduced by 0.037 to 0.055, 0.048 to 0.066, and 0.060 to 0.078 log CFU/day, respectively. Sorbate also extended the LPD and reduced the GR of L. monocytogenes at 8 and 12°C. Results indicated that sorbate concentration and pH level were significant factors affecting the LPD and GR of L. monocytogenes and that the combination of sorbate and low pH has potential for use as a surface treatment to control L. monocytogenes on meat surfaces.

KINETIKA PERTUMBUHAN MIKROBIA DAN KEMUNDURAN MUTU BAKSO DAGING TERLAPISI PATI UMBI KIMPUL (Xanthosoma sagittifolium)YANG DIINKORPORASI KALIUM SORBAT

The rapidity of microbial growth as damage agents indicates quality deterioration of food as its substrate. The presence of active coatings on the surface of the food material will affect to both of microbial growth rapidity and food quality deterioration. The objectives of this research were to determine the kinetics of microbial growth and quality deterioration of X. sagittifolium starch-based coated meatballs incorporated with potassium sorbate. Various potassium sorbate concentration onedible coatings were tested in the research. Observation parameters included the numberof microbes, protein content, TVB-N, weight losses, and texture. The results showed that the addition of potassium sorbate significantly affected the number of microbes, TVB-N, and texture. However, it did not significantly affect to the protein content and weight losses of meatballs. The number of microbes increased exponentially with the inhibitionrate of 0.101 times of potassium sorbate concentration, while TVB-N and the texture of meatballs changed linearly with the inhibition rate of 0.584 and 0.036 times of potassium sorbate concentration respectively. The active starch-based edible coatings with 0.6% potassium sorbate incorporated increased the shelf life of meatballs up to 4 days, while themeatballs without coating only lasted less than 1 day.Keywords: Active edible coating, microbial growth kinetics, potassium sorbate ABSTRAKKecepatan pertumbuhan mikrobia sebagai agen kerusakan dapat mengindikasikan kemunduran mutupangan sebagai substratnya. Adanya pelapis aktif pada permukaan bahan makanan akan mempengaruhi keduanya.Tujuan penelitian ini adalah untuk menentukan kinetika pertumbuhan mikrobia, dan kemunduran mutu bakso terlapisi pati umbi kimpul (X. sagittifolium) yang diinkorporasi kalium sorbat. Perlakuan yang dicoba dalam penelitian ini adalah konsentrasi kalium sorbat yang berbeda pada pelapis edible. Parameter pengamatan meliputi jumlah mikrobia, kadar protein, TVB-N, susut berat, dan tekstur.Hasil penelitian menunjukkan bahwa penambahan kalium sorbat berpengaruh nyata terhadap jumlah mikrobia, TVB-N, dan tekstur, serta berpengaruh tidak nyata terhadap kadar protein dan susut berat bakso. Jumlah mikrobia meningkat secara eksponensial dengan laju penghambatan 0,101 kali konsentrasi kalium sorbat, sementara TVB-N, dan tekstur bakso berubah secara linier dengan laju penghambatan masing-masing sebesar 0,584dan 0,036 kali konsentrasi kalium sorbat. Pelapis edible aktif berbasis pati X. sagittifolium yang diinkorporasi kalium sorbat 0,6% dapat meningkatkan umur simpan bakso sampai 4 hari, sementara bakso tanpa pelapis hanya bertahan kurang dari 1 hari.Kata kunci: Pelapis edible aktif, kinetika pertumbuhan mikrobia, kalium sorbat

Effect of Sodium Hypochlorite, Sodium Sorbate and Calcium Propionate Solutions on the Chestnut

The quadratic orthogonal rotation design with 3 factors was used to study the effect of sodium hypochlorite, sodium sorbate and calcium propionate solutions on the chestnut, and to establish the function model with 3 factors. The analysis on this model showed that the order of the effect of 3 factors was as follows: Calcium propionate > Sodium sorbate >Sodium hypochlorite; In this test, for getting over 55% good-fruit rate, respectively, the optimum sodium hypochlorite concentration was 11.4％－19.5％, sodium sorbate concentration was 2.67％－39.9％, calcium propionate concentration was 1.09％－2.71％.

Dynamic studies of nitrophenols adsorption on perfil in a fixed-bed column: application of single and two resistance model

The mechanism of 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP) adsorption on perfil—natural mineral taken from Bulgarian deposits, in a fixed-bed column was investigated. The single component experiments were conducted at constant initial sorbate concentration, volumetric flow rate, temperature and pH. The effect of adsorbent bed depth (Z 1, 2, 3, 6 cm) and sorbate nature on the adsorption capacity, mass transfer parameters and mechanisms was studied. The equilibrium behaviour of the system 4-NP-perfil was described by Langmuir, Freundlich and Redlich-Peterson models. The single resistance Thomas model, including Reynolds-Richards and Walter solutions, and the two-resistance Arnold model were applied for mathematical modeling of the experimental data. The comparative analyses indicated that external mass transfer was the rate limiting mechanism during the initial adsorption stages, while intraparticle diffusion was dominant in the middle and high concentration ranges. The effect of axial dispersion on the dynamics of adsorption was evaluated.

Regularities of Radioactive Barium from Water systems with Modified Hydrolytic Lingine

A method of hydrolytic lignine modification by treatment with sodium hydroxide concentrated solution has been proposed. The optimal conditions for production of the modified sorbent have been identified and influence of a number of factors upon the 133Ba sorption process in the static conditions have been considered, namely: values of ç, sorbent specific content and the sorbate concentration in the solution, time of contact between the liquid and the solid phases, hydrolytic lignine particle size, solution stirring intensity and alkaline metals salts presence. An outcome curve of the radionuclide sorption in the dynamic conditions has been obtained. It was demonstrated that the hydrolytic lignine was an effective sorbent in respect of radioactive 133Ba and could be used for water bodies protection against radionuclides.

Effects of Potassium Sorbate on Postharvest Brown Rot of Stone Fruit

The effect of potassium sorbate (K-sorb), a low-toxicity chemical, to control Monilinia spp. was investigated. Preliminary in vitro studies found the MIC of K-sorb for conidial germination and mycelial growth was, respectively, 260 and 1,250 mg/liter. Immersion of naturally infected peach and nectarine fruit in a solution (15 g/liter) of K-sorb for 120 s reduced brown rot by over 80% in four of five trials. Although treated fruits showed a significant reduction in firmness with respect to the control, they did not reach the overripe stage and retained acceptable quality parameters. In an attempt to elucidate the mechanism of action for K-sorb, the inhibition of enzymatic activity by K-sorb was also tested. In a radial diffusion assay, the addition of K-sorb to agarose reduced polygalacturonase (PG) activity across the concentrations considered. The greatest reduction (54.3%, with respect to the control) was obtained at a sorbate concentration of 15 g/liter. PG kinetic activity of Monilinia laxa observed by a spectrophotometric assay peaked after 40 min in all samples tested. PG activity was significantly higher in the control than in the samples with increased K-sorb concentrations. In conclusion, based on these findings, K-sorb can be recommended as a low-toxicity antifungal compound against Monilinia spp. in peaches and nectarines with its mode of action probably depending in part on the inhibition of PG activity in M. laxa.