Sorbate destruction and non-enzymatic browning in model aqueous systems Destruccion de sorbatos y pardeamiento no enzimático en sistemas modelo acuosos

The effect of system composition on sorbate destruction and sensory damage due to non-enzy matic browning was studied in aqueous model systems with a water activity ( aw) of 0.91 and a pH of 5.0-6.0. The rate constants of sorbate destruction could be described by first order kinetics and those from non-enzymatic browning by zero order kinetics. Both reactions were found to be related not only to temperature and pH but also to the humectants (NaCl, glycerol) used to depress aw. A higher preservative retention and a smaller amount of browning was produced by the use of a mixture of 35.0 g/kg of NaCl and 220.0 g/kg of glycerol as a humectant instead of one of them alone, citric acid instead of phosphoric acid as the acidifying agent, and glass flasks instead of polyethylene containers. The non-enzymatic browning reactions were greatly influenced by sorbic acid destruction. The inclusion of glycine was responsible for the enhanced sorbate destruc tion and browning development.

Download Full-text

Nota. Cinética de pardeamiento no enzimático de zumo de pera concentrado Note./ Non-enzymatic browning kinetics of concentrated pear juice

Food Science and Technology International ◽

10.1177/108201329700300309 ◽

1997 ◽

Vol 3 (3) ◽

pp. 213-218 ◽

Cited By ~ 4

Author(s):

A. Ibarz ◽

O. Martín ◽

G.V. Barbosa-Cánovas

Keyword(s):

Zero Order ◽

Enzymatic Browning ◽

First Order ◽

First Order Kinetics ◽

Zero Order Kinetics ◽

Soluble Solid ◽

Pear Juice ◽

Kinetics Of

Non-enzymatic browning kinetics of concentrated juice for three pear varieties (Alexandrine Douillard, Flor de Invierno and Blanquilla) was evaluated at three temperatures (90, 80 and 70 °C) and different soluble solid contents (52, 62 and 72 °Brix). The evolution of absorbance at 420 nm is described by zero order kinetics, but the formation of 5-hydroxymethyl-2 furfuraldehyde (HMF) and the reduction in formol index followed first order kinetics. The Alexandrine Douillard juices showed non-enzymatic browning which was less pronounced than in Flor de Invierno and Blanquilla juices.

Download Full-text

Parameters Effect on Photocatalytic Reduction Kinetics of Bromate in Aqueous Dispersion of TiO2

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.779-780.1658 ◽

2013 ◽

Vol 779-780 ◽

pp. 1658-1665

Author(s):

Rong Shu Zhu ◽

Fei Tian ◽

Ling Ling Zhang ◽

Ling Min Yu

Keyword(s):

Aqueous Dispersion ◽

Zero Order ◽

Photocatalytic Reduction ◽

Reduction Kinetics ◽

First Order ◽

First Order Kinetics ◽

Zero Order Kinetics ◽

Experimental Parameters ◽

Pseudo First Order ◽

Kinetics Of

This paper studied the photocatalytic reduction kinetics of bromate in aqueous dispersion of TiO2 and investigated the effects of experimental parameters, including initial concentration of BrO3-, pH, TiO2 dosage, anion and cation. The results indicate that the process of photocatalytic reduction of bromate follows a zero-order kinetics. In all the investigated experimental parameters, the initial bromate concentration, pH and anion have great effect on the photocatalytic reduction kinetics. The processes of photocatalytic reduction of bromate show the pseudo first-order kinetics at initial bromate concentration of 0.39 μmolL-1, pH=5.0, or in presence of HCO3-/CO32-, NO3-, SO42-, respectively.

Download Full-text

Use of purified lyophilized human lactate dehydrogenase isoenzymes in a study of the measurement of lactate dehydrogenase activity.

Clinical Chemistry ◽

10.1093/clinchem/32.5.758 ◽

1986 ◽

Vol 32 (5) ◽

pp. 758-762 ◽

Cited By ~ 1

Author(s):

D A Smith ◽

G C Moses ◽

A R Henderson

Keyword(s):

Lactate Dehydrogenase ◽

Zero Order ◽

Lactate Dehydrogenase Activity ◽

First Order ◽

First Order Kinetics ◽

Activity Concentrations ◽

Zero Order Kinetics ◽

Specific Activities ◽

The Stability ◽

Lactate Dehydrogenase Isoenzymes

Abstract We examined the stability of human lactate dehydrogenase (EC 1.1.1.27; LD) isoenzymes 1, 2, and 3--purified to specific activities of about 200 kU/g--when lyophilized in a buffered stabilized matrix of bovine albumin. Each isoenzyme was prepared at two activity concentrations and stored at -20, 4, 20, 37, and 56 degrees C for as long as six months. LD-1 activity decayed with zero-order kinetics, LD-2 and LD-3 with first-order kinetics. The extrapolated half-lives of these preparations at -20 degrees C varied between 80 and 530 years. Stability of reconstituted samples stored at 4 degrees C was excellent for LD-1 but poor for LD-2 and LD-3. We suggest that preparations of human LD-1 be further investigated as a possible reference material.

Download Full-text

Investigations into the kinetics and stoichiometry of bacterial oxidation of covellite (CuS) using a polarographic oxygen probe

Canadian Journal of Microbiology ◽

10.1139/m78-164 ◽

1978 ◽

Vol 24 (8) ◽

pp. 998-1003 ◽

Cited By ~ 5

Author(s):

Pamela A. D. Rickard ◽

Donald G. Vanselow

Keyword(s):

Oxygen Uptake Rate ◽

Zero Order ◽

Bacterial Oxidation ◽

Kinetics Of Oxidation ◽

First Order ◽

Cupric Ion ◽

First Order Kinetics ◽

Zero Order Kinetics ◽

Cupric Sulphate ◽

Kinetics Of

"Oxygraph" apparatus was used to measure quantitatively the kinetics of oxidation of synthetic covellite (CuS) in the presence and absence of Thiobacillus species. The expected stoichiometric relationship between oxygen consumed and cupric sulphate produced was verified by atomic absorption assays of cupric ion and sulphate ion. Thiobacillus cultures markedly increased the oxidation rate.The dependence of each oxygen-uptake rate on oxygen concentration was also measured. Sterile controls and some bacterial cultures showed first-order kinetics while other cultures showed zero-order kinetics.Addition of biological inhibitors to reacting slurries revealed that cultures showing first-order kinetics did not oxidize CuS itself but merely oxidized elemental sulphur formed by non-enzymic oxidation of CuS. Cultures showing zero-order kinetics oxidized CuS in a way that resulted in all oxygen reduction being enzymic. This mechanism possibly involves the cyclic oxidation and reduction of soluble iron.

Download Full-text

Ring-Opening Polymerization of ε-Caprolactone Using Novel Tin(II) Alkoxide Initiators

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.55-57.757 ◽

2008 ◽

Vol 55-57 ◽

pp. 757-760 ◽

Cited By ~ 4

Author(s):

A. Kleawkla ◽

Robert Molloy ◽

W. Naksata ◽

Winita Punyodom

Keyword(s):

Solid State ◽

Rate Constants ◽

Ring Opening ◽

Ring Opening Polymerization ◽

Zero Order ◽

Molecular Aggregation ◽

First Order ◽

First Order Kinetics ◽

Zero Order Kinetics ◽

Kinetics Of

Two novel tin(II) alkoxides, namely: tin(II) hexoxide, Sn(OC6H13)2, and tin(II) octoxide, Sn(OC8H17)2, have been synthesized for use as coordination-insertion initiators in the bulk ring-opening polymerization of ε-caprolactone. The kinetics of the polymerization reactions were studied at 140 °C by dilatometry. It was found that both alkoxides were slow to dissolve in the ε-caprolactone monomer due to their molecular aggregation in the solid state. As a result, the slow solubilization of the initiators gave rise to deviations from the expected first-order kinetics. Instead, the kinetic results adhered more closely to zero-order kinetics with apparent zero-order rate constants k0 of 6.58 x 10-2 and 4.63 x 10-2 mol l-1 min-1 for the hexoxide and octoxide respectively

Download Full-text

RBC Kinetics in Treating Domestic and Industrial Dairy Wastewater Under Low and High Organic Loading Conditions

Water Quality Research Journal ◽

10.2166/wqrj.1992.041 ◽

1992 ◽

Vol 27 (4) ◽

pp. 665-692 ◽

Cited By ~ 1

Author(s):

Rao Y. Surampalli ◽

E. Robert Baumann

Keyword(s):

Zero Order ◽

Dairy Wastewater ◽

Organic Load ◽

Secondary Effluent ◽

Normal Loading ◽

First Order ◽

Substrate Removal ◽

First Order Kinetics ◽

Zero Order Kinetics ◽

Rotating Biological Contactors

Abstract A full-scale, four-stage RBC (rotating biological contactors) plant, having parallel trains used to treat domestic and industrial dairy wastewater, failed to meet standard secondary effluent limits due to overloading in the two initial stages. The plant was first operated under normal loading; subsequently the load to the plant was increased in an incremental fashion by increasing the load from the dairy. This was done to evaluate the effectiveness of the use of supplemental aeration to eliminate oxygen-limiting conditions in the overloaded stages. An enlarged first stage was later created to lower the organic load to the initial stages by removing the wooden baffles between the first and second stages. The experimental work at the plant was conducted for approximately six months, during which daily 24-hour composite samples were collected at the end of each stage and analyzed for various parameters. The experimental results indicated that substrate removal with supplemental air and an enlarged first stage followed first-order kinetics at both lower and higher organic loadings. Without supplemental air, substrate removal followed second-order kinetics at lower loadings and zero-order kinetics at higher organic loadings. With an enlarged first stage only, substrate removal followed first-order kinetics at lower loading and zero-order kinetics at higher loadings. Overall, RBC performance improved significantly with supplemental air and an enlarged first stage. The results also suggest that higher organic loadings and removals can be achieved in the presence of supplemental air due to the maintenance of higher dissolved oxygen levels in the mixed liquor.

Download Full-text

The influence of hydrophylic polymers on the release rate of calcium dobesilate in hydrogel formulation assessed in vitro using porcine ear skin

Current Issues in Pharmacy and Medical Sciences ◽

10.1515/cipms-2015-0076 ◽

2015 ◽

Vol 28 (4) ◽

pp. 225-230 ◽

Cited By ~ 1

Author(s):

Dorota Wojcik-Pastuszka ◽

Anna Lisik ◽

Maria Twarda ◽

Ryszard Berkowski ◽

Witold Musial

Keyword(s):

Release Rate ◽

Hydroxypropyl Methylcellulose ◽

Zero Order ◽

Kinetics Model ◽

Calcium Dobesilate ◽

First Order ◽

Anionic Polymers ◽

First Order Kinetics ◽

Zero Order Kinetics

Abstract A shortage of available experimental data exists in the available bibliography on the release rate of calcium dobesilate (CD) from hydrogel formulations. Thus, the aim of the study was to evaluate the effect of selected hydrophilic nonionic polymers and anionic polymers on the release rate of CD from formulation provided for dermal application, as compared to the reference product in the market. The work utilized excised pork skin, while, Methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), and anionic polymers (copolymers of acrylic acid) were used as CD carriers. The release study was executed by the pharmacopoeial paddle method, with extraction cells and fresh excised porcine skin as a membrane. CD in aqueous acceptor fluid was quantified by UV-VIS spectrometry at 300 nm. Subsequently, the kinetic curves were fitted to a zero-order kinetics model, a first-order kinetics model, a second-order kinetics model, as well as to the Higuchi model. The work saw that porcine ear skin influences the release pattern of the CD, compared to the artificial membrane. In the study, the evaluated formulations with MC, polyacrylic acid (PA) and polyacrylate crosspolymer 11 (PC-11) deliver over 60% of the active component (AC), within 250 min, through the excised porcine ear skin, to the acceptor compartment. Moreover, the release observed via porcine ear skin to the aqueous acceptor compartment is congenial to zero-order or first-order kinetics. In addition, the formulations prepared on the basis of MC and PA appear to control AC delivery, independently of actual concentration of AC.

Download Full-text

Effects of initial concentration and irradiation dose to degradation of di butyl phthalate from phosphoric acid (30 % P2O5)

Radiochimica Acta ◽

10.1515/ract-2018-2984 ◽

2018 ◽

Vol 106 (11) ◽

pp. 909-916

Author(s):

Louisa Bounemia ◽

Abdelhamid Mellah

Keyword(s):

Organic Matter ◽

Phosphoric Acid ◽

Optimal Recovery ◽

Γ Irradiation ◽

Γ Radiation ◽

Initial Concentration ◽

First Order ◽

First Order Kinetics ◽

Butyl Phthalate

Abstract The pretreatment of the phosphoric acid is a stage of utmost importance leading to an optimal recovery of the uranium present in this acid. To this end, the degradation of the organic matter which obstructs considerably this recovery was tested by γ irradiation. This study lies within the scope of the radiation/matter interaction; concerning the use of the γ irradiator as proceed of phosphoric acid purification by the degradation of di butyl phthalate (DBP). Studies of the interaction of γ radiation with phosphoric acid solutions polluted by an organic matter concern the study of the influence of some parameters such as: dose rate (0.5–35 kGy), initial concentration (50–500 mg/L) of the pollutant, pH and % in P2O5 on the degradation of organic matter by γ irradiation. The reactions followed pseudo first order kinetics for different initial concentrations. The results made it possible to say that the degradation of di butyl phthalate by γ irradiation is dependent on the amount of the concentration of DBP and pH. The G-values decreased with absorbed doses, and increased with higher initial concentrations.Purification of phosphoric acid by γ radiation does not degrade the quality of this acid.

Download Full-text

Ag nanoparticles stabilized on cubic polyhedral oligomeric silsesquioxane cross-linked poly(N-isopropyl acrylamide-co-itaconic acid): An efficient catalyst for 4-nitrophenol reduction

Functional Materials Letters ◽

10.1142/s1793604720510406 ◽

2020 ◽

Vol 13 (07) ◽

pp. 2051040

Author(s):

Vahid Rahimkhoei ◽

Ali Akbari ◽

Maryam Zirak ◽

Bagher Eftekhari-Sis

Keyword(s):

Itaconic Acid ◽

Ag Nanoparticles ◽

Zero Order ◽

Polymeric Support ◽

Efficient Catalyst ◽

First Order ◽

First Order Kinetics ◽

Isopropyl Acrylamide ◽

Nitrophenol Reduction ◽

Oligomeric Silsesquioxane

Ag nanoparticles were synthesized and stabilized on a polymeric support, poly([Formula: see text]-isopropyl acrylamide-co-itaconic acid)/POSS, by simply reducing Ag[Formula: see text] ions adsorbed in the interior of the polymeric network. The prepared Ag@p(NIPAM-IA)/POSS was used as an efficient and recyclable catalyst for removal of the 4-nitrophenol (4-NP) contaminant by NaBH4-induced reduction to 4-aminophenol (4-AP) in aqueous solution. Different conditions including Ag content and amount of the nanocomposite, and also temperature of the 4-NP reduction were investigated. Also, two kinetic models, zero-order and first-order kinetics, were studied for the reduction of 4-NP to 4-AP.

Download Full-text

The Kinetics of Clearance from the Circulation of Man of Heparin and a Semi-Synthetic Heparin Analogue

10.1055/s-0039-1680541 ◽

1977 ◽

Author(s):

D. A. Lane ◽

R. Michalski ◽

V. V. Kakkar

Keyword(s):

High Specificity ◽

Antithrombotic Agent ◽

First Order ◽

First Order Kinetics ◽

Zero Order Kinetics ◽

Low Concentrations ◽

Equal Dose ◽

Rapid Clearance ◽

The Difference ◽

High Concentrations

A study has been made of a low molecular weight semi-synthetic heparin analogue, (SSHA) that may be clinically useful as an antithrombotic agent because of itsreported high specificity for potentiating antithrombin III activity. The clearance from the circulation of both heparin and the analogue has been studied in man following intravenous injection. Heparin obeyed almost zero order kinetics when assayed using a specific anti-Xa assay and first order kinetics when measured with KCCT. At high concentrations the heparin analogue was cleared with first order kinetics when assayed both with the anti-Xa assay and with KCCT. At low concentrations the analogue produced between one half and two-thirds of the anti-Xa activity of an equal dose of heparin, producing only a small prolongation of KCCT. With increasing dose, the more specific anti-Xa potentiating effect of SSHA decreased in part because of the difference in kinetic behaviour between heparin and SSHAbut largely because of a flattening of its anti-Xa dose response curve. Because of the initial more rapid clearance of higher doses of heparin from plasma when it is measured by the KCCT, these results suggest that the use of KCCT can cause a small underestimate of circulating heparin anti-thrombotic activity.

Download Full-text