Comparative Kinetic Study and Microwaves Non-Thermal Effects on the Formation of Poly(amic acid) 4,4'-(Hexafluoroisopropylidene)diphthalic Anhydride (6FDA) and 4,4'-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction Activated by Microwave, Ultrasound and Conventional Heating

Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system.     

Nanomaterials and the environment: a review for the biennium 2008-2010

Applications of nanotechnology are touching almost every aspect of modern life. The increased use of engineered nanomaterials (ENMs) in consumer products, chemical and medical equipment, information technology, and energy, among others, has increased the number of publications (informative and scientific) on ENMs. By the 1950s, very few papers were committed to nanomaterials (NMs), but in 2009, more than 80,000 journal articles included the concept nanotechnology. The objective of this review is to compile and analyze publications on NMs in the biennium 2008-2010. This review includes the most recent publications in risk assessment/toxicity, characterization and stability, toxicity, fate and transport of NMs in terrestrial ecosystems, and new ENMs. Carbon nanotubes, metallic, metal oxides and hydroxides nanoparticles, quantum dots, and polystyrene NPs are included.     

Comparison of Antimutagenic Activity of Phenolic Compounds in Newly Harvested and Stored Common Beans Phaseolus vulgaris against Aflatoxin B1

ABSTRACT: Phenolic compounds were extracted from recently harvested or stored black Jamapa beans ( Phaseolus vulgaris ) that were subjected or not to thermal treatment. The beans studied were cropped in the same area and were from the same lot. The highest amount of condensed tannins (CT) was found in the seed coat of recently harvested beans [222.41 ± 16mg of (+)-catechin equivalents per gram of seed coat]. After 2 yof storage, the amount of CT dropped significantly [35.8 ± 3.4 mg of (+) -catechin equivalents per gram of seed coat]. Thermal treatment significantly reduced the amount of CT in whole beans by approximately 70%. The raw seeds contained 13.76 ±1.2 mg of (+)-cat-echin equivalents per gram of seeds and a portion of CT appeared in the broth [9.4 ± 0.1 mg of (+) -catechin equivalents per gram of lyophilized broth]. The antimutagenic activity of these extracted phenolic compounds was tested against aflatoxin B₁ (AFB₁) in the Kado microsuspension assay. Newly harvested beans showed higher antimutagenic activity against AFB₁ mutagenicity than stored beans. The results suggest that to take the maximum advantage of components with biological activity present in beans, they must be used fresh.     

Frozen Foods Treated by Pressure Shift Freezing: Proteins and Enzymes

ABSTRACT: This work was focused on the changes that potatoes undergo after pressure shift freezing (PSF) treatment on protein content, peroxidase (POD), and polyphenoloxidase (PPO) enzymes. The samples were subjected to different conditions of P/T (210 MPa at −20°C; 180 MPa at −16°C; 150 MPa at −12°C; and 120 MPa at −8°C). Results showed that none of these conditions were enough to inactivate the POD and PPO enzymes. The POD was more resistant than PPO. Three isoenzymes of POD (61, 51, and 46 kDa) were detected. The protein content decreased about 50% after the PSF treatment at 210 MPa, −20°C; however, sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed 2 bands of about 21 kDa quite resistant to the treatment. On the contrary, mass spectrometry revealed among the resistant proteins, 2 fragments of pH 8.5 and about 20 kDa were more sensitive to 150 MPa, −12°C. The 2 fragments matched to a Solanum tuberosum proteinase inhibitor II protein     

Classification of unaltered and altered dry-cured ham by impedance spectroscopy: A preliminary study

The aims of this work were characterized by the physicochemical and microbiological features of dried-cured hams classified by the manufacturer as altered (deep spoilage and swollen) and unaltered, as well as, correlated these results with the electronic measurements of impedance spectroscopy, in order to lay the groundwork to design a suitable electrode to be used for checking in line all dry-cured ham elaborated. Double electrode and coaxial needle electrode were used in a frequency range of 100 Hz to 1 MHz. The electronic measurements of the two electrodes were able undoubtedly to discriminate between altered and unaltered dry-cured hams; moreover a tendency to classify between deep spoilage and swollen hams was shown. The values into the range of frequencies between 100 Hz–1000 Hz, for both electrodes, showed the best clustering results. More studies are needed to select the best electrode which can be transformed in a robust and versatile electrode which could be used for checking in line all dry-cured ham elaborated.     

Flow Cytometric Analysis of Oxidative Stress in Escherichia coli B Strains Deficient in Genes of the Antioxidant Defence

The detection of reactive oxygen species (ROS) and the analysis of oxidative stress are frequent applications of functional flow cytometry. Identifying and quantifying the ROS species generated during oxidative stress are crucial steps for the investigation of molecular mechanisms underlying stress responses. Currently, there is a wide availability of fluorogenic substrates for such purposes, but limitations in their specificity and sensitivity may affect the accuracy of the analysis. The aim of our work was to validate a new experimental model based in different strains of Escherichia coli B deficient in key genes for antioxidant defense, namely oxyR, sodA and sodB. We applied this model to systematically assess issues of specificity in fluorescent probes and the involvement of different ROS in a bacterial model of oxidative stress, as the probes can react with a variety of oxidants and free radical species. Our results confirm the higher sensitivity and specificity of the fluorescent probe mitochondrial peroxy yellow 1 (MitoPY1) for the detection of H₂O₂, and its very low capacity for organic hydroperoxides, thus extending MitoPY1′s specificity for H₂O₂ in mammalian cells to a bacterial model. On the contrary, the fluorescent probe 2′,7′-dichlorodihydrofluorescein diacetate (H₂DCF-DA) is more sensitive to organic peroxides than to H₂O₂, confirming the lack of selectivity of H₂DCF-DA to H₂O₂. Treatment with organic peroxides and H₂O₂ suggests a superoxide-independent oxidation of the fluorescent probe Hydroethidine (HE). We found a positive correlation between the lipophilicity of the peroxides and their toxicity to E. coli, suggesting greater quantitative importance of the peroxidative effects on the bacterial membrane and/or greater efficiency of the protection systems against the intracellular effects of H₂O₂ than against the membrane oxidative stress induced by organic peroxides. Altogether, our results may aid in preventing or minimizing experimental errors and providing recommendations for the proper design of cytometric studies of oxidative stress, in accordance with current recommendations and guidelines.     

In vitro gastrointestinal digestion of mango by-product snacks: Potential absorption of polyphenols and antioxidant capacity

Mango by-products are considered cheap sources of valuable foods and nutraceutical ingredients. In this work, antioxidant capacity (AOX), and potential absorption ability (PAA) of extractable polyphenols (EP) from mango by-product snacks (MB-S) were evaluated at different stages of in vitro gastrointestinal digestion. A wheat and oat-based control snack and three MB-S formulations (F1, F2 and F3) were prepared. Mango by-products were added at the expense of wheat in MB-S (paste-peel-seed): F1 (70-30-0), F2 (70-15-15), F3 (70-7.5-22.5). The highest release of polyphenols was observed after the gastric digestion. In the intestinal stage, MB-SF1 was the snack with the highest EP content (23.39 mg GAE/g db), two times greater than the control. Gallic acid and mangiferin were the main polyphenols identified in MB-S. The incorporation of mango seed in the MB-S reduced the polyphenols PAA by 10.29%. However, compared with the control snack, consumption of 30 g MB-SF1 provided additional 45 mg polyphenols.     

Relationship between lysyl oxidase activity,pyridinoline content and muscle texture during ice storage of jumbo squid (Dosidicus gigas)

Collagen fibres, stabilised by lysyl oxidase (LOX), play an important role in jumbo squid because they are responsible for the union between various cells; therefore, a close interdependence between their functions and muscle firmness during ice storage has been suggested. In this study, the relationship between LOX activity, pyridinoline (Pyr) content and muscle texture (SF) during ice storage of jumbo squid mantle was evaluated. LOX activity was confirmed within the range of 4.1–7.1 × 10^?3 U g^?1 of protein, leading to an increase in Pyr content, detected in the range of 0.85–1.32 mmol mol^?1 of collagen after 5–20 days. The SF of the muscle became harder during the ice storage time, increasing from 21.08 to 37.95 N. It was therefore possible to establish the relationship between LOX activity, collagen cross‐links (Pyr content) and texture patterns during ice storage of jumbo squid muscle, which increased after 20 days.