scholarly journals Journal of Food Quality Thermal Degradation of Plum Anthocyanins: Comparison of Kinetics from Simple to Natural Systems

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Mihaela Turturică ◽  
Nicoleta Stănciuc ◽  
Claudia Mureșan ◽  
Gabriela Râpeanu ◽  
Constantin Croitoru
Keyword(s):  
Antioxidant Activity ◽  
Citric Acid ◽  
Thermal Degradation ◽  
Fluorescence Spectra ◽  
Degradation Rate ◽  
Natural Systems ◽  
Degradation Rate Constant ◽  
Higher Temperature ◽  
Lower Temperature ◽  
The Stability

The stability of anthocyanin was assessed over a temperature range of 50–120°C in different simulated plum juices in order to compare the thermal behavior in the presence of certain compounds. The results were correlated with the antioxidant activity and intrinsic fluorescence spectra. The results suggested significant changes, especially at higher temperature; hence, increase in the fluorescence intensity and some bathochromic and hypsochromic shifts were observed. Anthocyanins in natural matrices presented the highest rate for degradation, followed by the anthocyanins in juices with sugars. Values of the activation energies were 42.40 ± 6.87 kJ/mol for the degradation in water, 40.70 ± 4.25 kJ/mol for the juices with citric acid, 23.03 ± 3.53 kJ/mol for the juices containing sugars, 35.99 ± 3.60 kJ/mol for simulated juices with mixture, and 14.19 ± 2.39 kJ/mol for natural juices. A protective effect of sugars was evidenced, whereas in natural matrices, the degradation rate constant showed lower temperature dependence.

Thermal degradation of EDTA chelates in aqueous solution

1982 ◽  
Vol 60 (10) ◽  
pp. 1207-1213 ◽  
Author(s):  
Ramunas J. Motekaitis ◽  
X. B. Cox III ◽  
Patrick Taylor ◽  
Arthur E. Martell ◽  
Brad Miles ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Thermal Degradation ◽  
Elevated Temperatures ◽  
Degradation Products ◽  
Iminodiacetic Acid ◽  
Reaction Products ◽  
Degradation Rates ◽  
Lower Temperature Range ◽  
Higher Temperature ◽  
Lower Temperature

The thermal degradation of Ca(II), Mg(II), Zn(II), Fe(II), and Ni(II) chelates of EDTA was investigated in alkaline aqueous solution at elevated temperatures (230–310 °C). The kinetics of decomposition were followed by nmr, titrimetry, and spectrophotometry. Reaction products were identified through nmr and by gas chromatography. The relative order of degradation rates, as measured by the loss of EDTA, was found to be Mg(II) > Ca(II) > Zn(II) > Fe(II) > Ni(II). The main degradation products formed in the lower temperature range (~250 °C) are iminodiacetic acid, hydroxyethyliminodiacetic acid, and ethylene glycol. Higher temperature products are primarily dimethylamine and carbon dioxide. The rates of degradation of Ca(II), Mg(II), and Zn(II) EDTA chelates are considerably enhanced when either phosphate is present or a glass-lined autoclave is employed.

scholarly journals pH effect on stability and kinetics degradation of nitazoxanide in solution

2020 ◽  
Vol 4 (1) ◽  
pp. 12-17
Author(s):  
Fábio Barbosa ◽  
Leonardo Pezzi ◽  
Julia Sorrentino ◽  
Martin Steppe ◽  
Nadia Volpato ◽  
...  
Keyword(s):  
Rate Constant ◽  
Degradation Product ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Ph Effect ◽  
Degradation Rate Constant ◽  
Main Degradation Product ◽  
Wide Ph Range ◽  
The Stability ◽  
Ph Range

Stability studies correspond to a set of tests designed to assess changes in the quality of a given drug over time and under the influence of a number of factors. Among these factors, pH plays an important role, due to the catalytic effect that hydronium and hydroxide ions can play in several reactions. In the present study, the degradation kinetics of nitazoxanide was evaluated over a wide pH range, and the main degradation product generated was identified by LC-MS/MS. Nitazoxanide showed first-order degradation kinetics in the pH range of 0.01 to 10.0 showing greater stability between pH 1.0 and 4.0. The degradation rate constant calculated for these pH was 0.0885 x 10-2 min-1 and 0.0689 x 10-2 min-1, respectively. The highest degradation rate constant value was observed at pH 10.0 (0.7418 x 10-2 min-1) followed by pH 0.01 (0.5882 x 10-2 min-1). A major degradation product (DP-1) was observed in all conditions tested. Through LC-MS/MS analysis, DP-1 was identified as a product of nitazoxanide deacetylation. The effect of pH on the stability of nitazoxanide and the kinetic data obtained contribute to a better understanding of the intrinsic stability characteristics of nitazoxanide.

Poly(3-hydroxybutyrate) - Organo Modified Montmorillonite Nanohybrid; Preparation and Characterization

2012 ◽  
Vol 622-623 ◽  
pp. 263-270 ◽  
Author(s):  
Ali Salehabadi ◽  
Mohamad Abu Bakar
Keyword(s):  
Thermal Degradation ◽  
Degradation Rate ◽  
Solvent Casting ◽  
X Ray Diffraction ◽  
X Ray ◽  
Casting Technique ◽  
Modified Montmorillonite ◽  
Degradation Rate Constant ◽  
Degradation Activation Energy ◽  
Silicate Layers

Nano-biohybrid, based on biodegradable polyester, poly (3-hydroxybutyrate) (PHB), and a commercial organo modified montmorillonite (MMT), were prepared by solvent casting technique. Morphology and non-isothermal degradation of PHB and PHB/MMT hybrids were characterized by POM and TG-DTG technique. In the composite materials, an increase MMT loading in the PHB decreased the onset temperature (Tonset) of thermal degradation, while it achieved higher values upon increasing the heating rate. Kissinger plots deduced a trend of the degradation activation energy, Ed, which was related to the agglomeration of MMT. The thermal degradation rate constant, k, was related to the MMT loading in PHB. X-ray diffraction analysis confirmed the expansion of MMT silicate layers.

scholarly journals Vitamin C stability in acerola and camu-camu powder obtained by spray drying

2020 ◽  
Vol 23 ◽  
Author(s):  
Vitor Augusto dos Santos Garcia ◽  
Josiane Gonçalves Borges ◽  
Fernanda Maria Vanin ◽  
Rosemary Aparecida de Carvalho
Keyword(s):  
Antioxidant Activity ◽  
Vitamin C ◽  
Spray Drying ◽  
Physicochemical Characteristics ◽  
Storage Conditions ◽  
High Vitamin ◽  
Industry Applications ◽  
High Antioxidant Activity ◽  
Lower Temperature ◽  
The Stability

Abstract Acerola and camu-camu fruits possess high vitamin C content. However, since these fruits are little consumed in their fresh form, it is important to consider that vitamin C can be oxidized depending on storage conditions. Thus, this study aimed to produce acerola and camu-camu powders by spray drying to maintain the stability of their vitamin C content during storage. Acerola and camu-camu powders were characterized in relation to their physicochemical characteristics, antioxidant activity, and vitamin C concentration and stability under different storage conditions (30 °C and 40 °C, 75% relative humidity). In general, the powders were proven to be stable, with low water activity (< 0.40) and humidity (< 4.0 g/100 g powder), as well as high vitamin C concentrations (1593.2 and 6690.4 mg/100 g of powder for acerola and camu-camu, respectively). Furthermore, we observed a high antioxidant activity by ABTS●+, DPPH• and FRAP assays. The powders stored at lower temperature (30 °C) showed higher vitamin C stability. In conclusion, acerola and camu-camu powders produced by spray drying are potential sources of vitamin C and active compounds and are therefore suitable for several food industry applications.

The thermal degradation behavior of meta- and para- hetero-amide fibers by TGA-FTIR

2013 ◽  
Vol 33 (4) ◽  
pp. 337-344 ◽  
Author(s):  
Ning Sun ◽  
Yinxing Liang ◽  
Zhaohua Xu ◽  
Heng Li ◽  
Jiang Shaohua ◽  
...  
Keyword(s):  
Thermal Degradation ◽  
Degradation Behavior ◽  
Leading Role ◽  
Degradation Temperature ◽  
Thermal Degradation Behavior ◽  
Different Temperatures ◽  
Degradation Behaviors ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Hydrolytic Mechanism

Abstract The thermal degradation behaviors of poly-p-phenylene-benzimidazole-terephthalamide (PBIA), poly-m-phenylene isophthalamide (PMIA) and poly-p-phenylene terephthalamide (PPTA) fibers are investigated by thermogravimetric analysis (TGA) coupled with Fourier transform infrared spectroscopy (TGA-FTIR). The results demonstrate that PBIA fiber exhibits better thermal- and thermo-oxidative stability than that of the other two polymers. PBIA shows the highest onset degradation temperature, both in nitrogen and air. TGA-FTIR provides information on compositions of pyrolyzates and their relationship with the structures of polyamides. Analysis of the compositions and distributions of all pyrolyzates, at different temperatures, indicates that a hydrolytic mechanism plays a leading role at lower temperature, and a homolytic mechanism is dominant at higher temperature.

Radix Pseudostellariae protein-curcumin nanocomplex: Improvement on the stability, cellular uptake and antioxidant activity of curcumin

2021 ◽  
Vol 151 ◽  
pp. 112110
Author(s):  
Xixi Cai ◽  
Qingxia Weng ◽  
Jiaming Lin ◽  
Guiqing Chen ◽  
Shaoyun Wang
Keyword(s):  
Antioxidant Activity ◽  
Cellular Uptake ◽  
The Stability

scholarly journals Effect of food processing on the antioxidant activity of flavones from Polygonatum odoratum (Mill.) Druce

2021 ◽  
Vol 16 (1) ◽  
pp. 92-101
Author(s):  
Guanghui Xia ◽  
Xinhua Li ◽  
Zhen Zhang ◽  
Yuhang Jiang
Keyword(s):  
Antioxidant Activity ◽  
High Pressure ◽  
Food Processing ◽  
Yeast Fermentation ◽  
Pressure Treatment ◽  
Processing Methods ◽  
High Pressure Treatment ◽  
Effect Of Food ◽  
The Stability

Abstract Polygonatum odoratum (Mill.) Druce (POD) is a natural plant widely used for food and medicine, thanks to its rich content of a strong antioxidant agent called homoisoflavones. However, food processing methods could affect the stability of POD flavones, resulting in changes to their antioxidant activity. This study attempts to evaluate the antioxidant activity of POD flavones subject to different processing methods and determines which method could preserve the antioxidant activity of POD flavones. Therefore, flavones were extracted from POD samples, which had been treated separately with one of the four processing methods: extrusion, baking, high-pressure treatment, and yeast fermentation. After that, the antioxidant activity of the flavones was subject to in vivo tests in zebrafish embryos. The results show that yeast fermentation had the least disruption to the antioxidant activity of POD flavones, making it the most suitable food processing method for POD. By contrast, extrusion and high-pressure treatment both slightly weakened the antioxidant activity of the flavones and should be avoided in food processing. The research results provide a reference for the development and utilization of POD and the protection of its biological activity.

scholarly journals Complexes of Copper and Iron with Pyridoxamine, Ascorbic Acid, and a Model Amadori Compound: Exploring Pyridoxamine’s Secondary Antioxidant Activity

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 208
Author(s):  
Guillermo García-Díez ◽  
Roger Monreal-Corona ◽  
Nelaine Mora-Diez
Keyword(s):  
Antioxidant Activity ◽  
Ascorbic Acid ◽  
Rate Constant ◽  
Stable Complex ◽  
Aqueous Environment ◽  
Oh Radicals ◽  
Bidentate Ligands ◽  
Superoxide Radical Anion ◽  
Amadori Compound ◽  
The Stability

The thermodynamic stability of 11 complexes of Cu(II) and 26 complexes of Fe(III) is studied, comprising the ligands pyridoxamine (PM), ascorbic acid (ASC), and a model Amadori compound (AMD). In addition, the secondary antioxidant activity of PM is analyzed when chelating both Cu(II) and Fe(III), relative to the rate constant of the first step of the Haber-Weiss cycle, in the presence of the superoxide radical anion (O2•−) or ascorbate (ASC−). Calculations are performed at the M05(SMD)/6-311+G(d,p) level of theory. The aqueous environment is modeled by making use of the SMD solvation method in all calculations. This level of theory accurately reproduces the experimental data available. When put in perspective with the stability of various complexes of aminoguanidine (AG) (which we have previously studied), the following stability trends can be found for the Cu(II) and Fe(III) complexes, respectively: ASC < AG < AMD < PM and AG < ASC < AMD < PM. The most stable complex of Cu(II) with PM (with two bidentate ligands) presents a ΔGf0 value of −35.8 kcal/mol, whereas the Fe(III) complex with the highest stability (with three bidentate ligands) possesses a ΔGf0 of −58.9 kcal/mol. These complexes can significantly reduce the rate constant of the first step of the Haber-Weiss cycle with both O2•− and ASC−. In the case of the copper-containing reaction, the rates are reduced up to 9.70 × 103 and 4.09 × 1013 times, respectively. With iron, the rates become 1.78 × 103 and 4.45 × 1015 times smaller, respectively. Thus, PM presents significant secondary antioxidant activity since it is able to inhibit the production of ·OH radicals. This work concludes a series of studies on secondary antioxidant activity and allows potentially new glycation inhibitors to be investigated and compared relative to both PM and AG.

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