Reduced coke formation and aromaticity due to chloroperoxidase-catalyzed transformation of asphaltenes from Maya crude oil

The transformation of the porphyrin-free asphaltene fraction from a heavy Maya crude oil was catalyzed by chloroperoxidase from Caldariomyces fumago (CPO) in a ternary system with low water content of 6.3%. The total turnover number (TTN) in this system was determined for lyophilized CPO in the presence of sucrose as cryoprotector and for a covalent bioconjugate with chitosan. The covalent conjugation of CPO with chitosan increased the TTN by 10-fold. Fluorescence due to aromatic groups decreased by 24% in treated asphaltenes, indicating significant changes after the biotransformation. On the other hand, the solubility profile indicated that transformed asphaltenes are less soluble in toluene and more prone to precipitate in the presence of hexane, compared to untreated asphaltenes, which could be related to the introduction of polar atoms. Energy-dispersive X-ray spectroscopy (EDS) showed that the content of chlorine increased six-fold on an atomic basis. Finally, enzymatically transformed asphaltenes are more reactive and thus generate less coke, as evidenced by thermal degradation under nitrogen atmosphere.     

Deposition of a-C:N films and evaluation of their robustness in electrochemical applications

A multilayer a-C:N film electrode deposition process has been developed using the filtered cathodic vacuum arc (FCVA) system based on the highly conductive silicon wafer with a Ti interlayer for ohmic contacts. Its robustness has been evaluated under the practical electrochemical conditions and shows that it has no pin-hole and no breaking point happened when voltages are applied on it. Extremely large errors will arise in the electrochemical characterizing a-C:N film electrodes (hydrogen and oxygen evolutions and oxygen reduction) when there is a pin-hole or a broken point in the films. And the error caused by the non-ohmic contact amplifies at a high potential range. It is expected that non-robust a-C:N film electrodes and non-ohmic contacts mislead the electrochemical characterizing on a-C:N films.     

Electron beam effects on amorphous molybdenum oxide nanostructures grown by condensation in hydrogen

Molybdenum trioxide (MoO₃) was evaporated from a tungsten resistive source in presence of hydrogen as carrier gas at pressures from 100 Pa to 600 Pa. Crystalline samples of molybdenum oxide were obtained at source temperatures below 950 °C. However, at source temperatures above 1000 °C, nanoporous structures were obtained, with porosity in the range of 10–85 nm. As shown by X-ray diffraction as well as selected area electron diffraction (SAED), the nanoporous material was amorphous. Under transmission electron microscopy (TEM) examination, and due to the electron beam, progressive formation of crystalline clusters was observed, as revealed by sequential changes of SAED and dark field images and corroborated in the high resolution TEM images (HRTEM). The growth of crystalline clusters at the nanometer scale occurs without destruction of the nanoporous structures.     

Oil chemical variation in walnut (Juglans regia L.) genotypes grown in Argentina

Walnut (Juglans regia L.) oil (WO) from the varieties Chandler, Franquette, Hartley, Lara, Mayette, Serr, Sorrento and Tulare were studied in order to evaluate genotypical variations in fatty acid (FA) and volatile compositions, tocopherol content and oxidative parameters. Oil content was found to range between 71.4 and 73.9%. Oils obtained by pressing presented low acid (0.05–0.22% oleic acid), peroxide (0.05–0.47 meq O₂/kg oil), K₂₃₂, and K₂₇₀ values, and moderate (247–365 µg/g oil) total tocopherol contents. Variations in unsaturated fatty acid contents were between 16.1 and 25.4% (oleic acid), 52.5 and 58.9% (linoleic acid), and 11.4 and 16.5% (linolenic acid). Oxidative stability (OS), as measured by the Rancimat method, was poor (2.64–3.44 h) and it correlated positively with oleic and negatively with linolenic acid contents. In contrast to their low OS, the antioxidant capacity evaluated through the 2,2‐diphenyl‐1‐picrylhydrazyl radical assay showed that the WO analyzed here have good radical‐scavenging activity. Tocopherols appear to be the most important contributors to this biochemical property. The findings connected with volatile composition showed a similar qualitative pattern where aldehydes were present at higher concentration. Most of them seem to come from unsaturated FA mainly through a chemical pathway.     

Fresh cut ‘Tommy Atkins’ mango pre-treated with citric acid and coated with cassava (Manihot esculenta Crantz) starch or sodium alginate

This work aimed to evaluate quality parameters of ‘Tommy Atkins’ mango slices pre-treated with citric acid and cassava starch or sodium alginate edible coatings, with or without glycerol. Samples only treated with citric acid were also evaluated. Mango slices dipped in sanitising solution were used as control. Colour parameters, mechanical properties, weight loss and respiration rate were analysed during 15 days at 5 °C. Cassava starch coating, with or without glycerol, provided higher stress at failure and lightness values than control sample throughout storage (p ≤ 0.05). The citric acid promoted colour preservation, but increased significantly samples weight loss during storage. Sodium alginate coatings did not maintain quality characteristics, showing stress at failure and lightness values lower than control after 15 days. All coatings reduced respiration rate, but citric acid dipping and cassava starch coating without glycerol treatments were more effective, reaching values around 41% lower, when compared to control sample.

Industrial Relevance

Fresh-cut mangoes are appreciated world-wide for its exotic flavour and nutritional composition. However, their shelf life is limited by changes in colour, texture, appearance and microbial growth. The edible coatings act as gas and water vapour barrier, extending the storage time of fresh-cut fruit and vegetables. Thus, cassava starch and alginate are alternatives to preserve minimally processed mangoes, maintaining the quality parameters of fresh fruit. This work is useful for the minimal processing industry in order to increase shelf life of fresh-cut mangoes, which can be considered an alternative to fast food and other ready-to-eat products, attending the demand for healthy and convenient foodstuffs.     

Effects of aerobic training,resistance training,or combined resistance‐aerobic training on the left ventricular myocardium in a rat model

This study follows the left ventricular (LV) hypertrophy in rats undergoing aerobic training alone (A), resistance training alone (R), or combined resistance and aerobic training (RA) (usually referred as concurrent training) program. A sedentary control group (C) was included. LV remodeling was evaluated using electron and light microscopy. The LV weight to body weight (LVW: BW) increased 11.4% in A group, 35% in the R group, and 18% in the RA group compared to the C group. The LV thickness increased 6% in the A group, 17% in the R group, and 10% in the RA group. The LV internal diameter increased 19% in the A group, 3% in the R group, and 8% in the RA group compared with the C group. The cross‐sectional area of cardiomyocyte increased by 1% with the A group, 27% with R group, and 12% with RA training. The capillary density increased by 5.4% with A training, 11.0% with R training, and 7.7% with RA training compared with the C group. The volume fraction of interstitial collagen increased by 0.4% with training A, increased by 2.8% with R training, and 0.9% with RA training. In conclusion, except for the LV internal diameter, which increased more in the A group, the cardiac parameters increased more in the R group than in the other groups and in RA group than in A group. Collagen density increased from 5.4 ± 0.8% in the C group to 5.8 ± 0.6% in the A group (n. s.) (P > 0.05), to 8.2 ± 0.7% in the R group (P < 0.05), and to 6.3 ± 0.4% in the RA group (P < 0.05). These results demonstrate a significant increase for collagen content in the LV with R and RA exercise, but the increase was higher with R training alone than with RA training. Microsc. Res. Tech. 77:727–734, 2014. © 2014 Wiley Periodicals, Inc.     

Addition of sodium caseinate to skim milk inhibits rennet-induced aggregation of casein micelles

The objective of this paper was to observe the rennet-induced aggregation behaviour of casein micelles in milk in the presence of additional sodium caseinate. Analysis of the centrifugal supernatants by size exclusion chromatography confirmed an increase in the soluble protein in the milk serum phase after addition of sodium caseinate. Although the total amount of κ-casein hydrolyzed over time was not affected, there was a significant effect of soluble casein on milk gelation, with a dose-dependent decrease of the gelation time as measured by rheology. Light scattering experiments also confirmed that the addition of soluble caseins inhibited the aggregation of casein micelles. Addition of 1 mM CaCl₂ prior to renneting increased the extent of rennet aggregation in samples containing additional sodium caseinate, but the inhibiting effect was still evident. The amount of soluble casein (as measured by chroma tography) significantly decreased after renneting, suggesting its association with the micellar fraction. Supporting experiments carried out with purified fractions of soluble caseins demonstrated that both α_s-casein and β-casein played a role as protective colloids (increasing steric repulsion) during renneting. It was concluded that the inhibiting effect observed during gelation was caused by the adsorption of soluble casein molecules on the surface of rennet-altered casein micelles.