Morphology and mechanical properties of nanocomposites of cellulose acetate and organic montmorillonite prepared with different plasticizers

Nanocomposites of cellulose acetate and an organically modified montmorillonite (CA/MMTO) were prepared by melt intercalation in a twin‐screw extruder, using two different plasticizers: di‐octyl phthalate (DOP) and triethyl citrate (TEC). The influence of plasticizer type and the organoclay added to the structure, the morphology, and the thermal properties of the nanocomposites was investigated. XRD and SAXS results indicated a significant CA or/and plasticizer intercalation in the clay gallery for the CA/MMTO nanocomposites. In addition, the images obtained by TEM show that the morphology of CA/MMTO nanocomposites is made up of intercalated and exfoliated silicate layers. The glass transition temperature (T_g) of CA with DOP or TEC decreased in at almost same value, which shows the characteristics of both additives as plasticizers for cellulose acetate chains. Tensile tests indicate that the nanocomposites with either of the two plasticizers presented the same performance with respect to material properties. The results demonstrated that, for some applications, TEC is an useful alternative to plasticize CA in order to substitute DOP, a non eco‐friendly plasticizer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Determination of halogens in coal after digestion using the microwave-induced combustion technique

The microwave-induced combustion (MIC) technique was applied for coal digestion and further determination of bromide, chloride, fluoride, and iodide by ion chromatography (IC). Samples (up to 500 mg) were combusted at 2 MPa of oxygen. Combustion was complete in less than 50 s, and analytes were absorbed in water or (NH(4))(2)CO(3) solution. A reflux step was applied to improve analyte absorption. Accuracy was evaluated for Br, Cl, and F using certified reference coal and spiked samples for I. For Br, Cl, and F, the agreement was between 96 and 103% using 50 mmol L(-1) (NH(4))(2)CO(3) as the absorbing solution and 5 min of reflux. With the use of the same conditions, the recoveries for I were better than 97%. Br, Cl, and I were also determined in MIC digests by inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry, and F was determined by an ion-selective electrode with agreement better than 95% to the values obtained using IC. Temperature during combustion was higher than 1350 degrees C, and the residual carbon content was lower than 1%. With the use of the MIC technique, up to eight samples could be processed simultaneously, and a single absorbing solution was suitable for all analytes and determination techniques (limit of detection by IC was better than 3 microg g(-1) for all halogens).     

Incorporation of Lactobacillus acidophilus in Minas fresh cheese and its implications for textural and sensorial properties during storage

The effect of Lactobacillus acidophilus on instrumental texture profile and related properties of Minas fresh cheese during storage at 5 °C and on sensory performance was investigated. Four cheese-making trials were prepared, two supplemented with a mesophilic type O culture (T1, T2) and two with lactic acid (T3, T4). L. acidophilus was added in T2 and T3. The viability of L. acidophilus, instrumental texture profile analysis and related properties were monitored during storage for up to 21 days. Probiotic cheeses T3 were firmer by the end of storage, due to higher values of pH and hardness. Differences detected were attributed to the starter, rather than to L. acidophilus. Viability of L. acidophilus during storage ranged from 6.04 to 6.93 for T2 and from 5.46 to 6.53 log cfu g⁻¹ for T3, which performed better in sensory evaluation. Minas fresh cheese is a suitable food system for the delivery of L. acidophilus.     

Phenolic composition in different genotypes of Guabiju fruits (Myrcianthes pungens) and their potential as antioxidant and antichemotactic agents

Fruits of Myrcianthes pungens Berg. Legr. (Myrtaceae), known as guabiju, are widely consumed fresh as well as dried, processed into jam, marmalade, and juices. In this study, chemical composition and antichemotactic and antioxidant activities of fruits from a wild type (GB) and 2 genotypes, PL2 and PL1, of guabiju were investigated. Total anthocyanins for the genotypes ranged from 334 to 531 mg/100 g dry weight (dwt). Total flavonoids and polyphenols ranged from 79.8 to 154 mg/100 g and 2438 to 4613 mg/100 g (dwt), respectively. A reversed phase liquid chromatography method with photodiode array detection was used to determine chemical profiles of the main anthocyanins found in the extracts. An HPLC method for the quantification of flavonoids is proposed, providing a simple procedure with rapid sample preparation. All samples contained 5 identical anthocyanidins, distributed differently, with cyanidin as the main compound. Identified flavonoids were quercitrin, hyperoside, and isoquercitrin; their relative amounts varied among the extracts. The antioxidant activity of guabiju methanolic extract was comparable to that of Trolox, and at a test concentration of 0.25 mg/mL, GB and PL2 activities were higher than those exhibited by Trolox. Total dry extracts of guabiju exhibited greater inhibition of chemotaxis at a concentration of 4 μg/mL, except for GBH (wild-type hydrolyzed extract) which already presented high values at a concentration of 2 μg/mL. These results suggest that the consumption of this fruit, rich in polyphenols, may be beneficial to human health. Practical Application: The paper is the first attempt on the improvement of this native fruit, since it is widely consumed regularly as part of the South American diet. The content of phenolic compounds demonstrates that consumption of guabiju would be beneficial to human health. Differences among samples, originating from open pollination of plants growing on the same site, lead to the conclusion that improvements can be made in the chemical composition and beneficial activity of guabiju fruits by simply selecting genotypes for these characteristics among open-pollinated seedlings.     

Sulfate threshold target to control methylmercury levels in wetland ecosystems

Sulfate contamination has a significant environmental implication through the stimulation of toxic hydrogen sulfide and methylmercury (MeHg) production. High levels of MeHg are a serious problem in many wetland ecosystems worldwide. In the Florida Everglades, it has been demonstrated that increasing MeHg occurrence is due to a sulfate contamination problem. A promising strategy of lowering the MeHg occurrence is to reduce the amount of sulfate entering the ecosystem. High surface water sulfate concentrations in the Everglades are mainly due to discharges from the Everglades Agricultural Area (EAA) canals. Water and total sulfur mass balances indicated that total sulfur released by soil oxidation, Lake Okeechobee and agricultural application were the major sources contributing 49,169, 35,217 and 11,775 mtons year^− 1, respectively. Total sulfur loads from groundwater, levees, and atmospheric deposition contributed to a lesser extent: 4055; 5858 and 4229 mtons year^− 1, respectively. Total sulfur leaving the EAA into Water Conservation Areas (WCAs) through canal discharge was estimated at 116,360 mtons year⁻¹, and total sulfur removed by sugarcane harvest accounted for 23,182 mtons year^− 1. Furthermore, a rise in the mineral content and pH of the EAA soil over time, suggested that the current rates of sulfur application would increase as the buffer capacity of the soil increases. Therefore, a site specific numeric criterion for sulfate of 1 mg L^− 1 was recommended for the protection of the Everglades; above this level, mercury methylation is enhanced. In parallel, sulfide concentrations in the EAA exceeded the 2 μg L^− 1 criterion for surface water already established by the U.S. Environmental Protection Agency (EPA).     

Supercritical fluid extraction of grape seed: Process scale-up, extract chemical composition and economic evaluation

The scale-up of the supercritical fluid extraction (SFE) process for grape (Vitis vinifera L.) seed was studied from the laboratory (0.29 L) to the pilot scale (5.15 L) at 35 MPa and 313 K. The scale-up criterion adopted consisted of maintaining a constant solvent to feed ratio (S/F), and the criterion was successfully used to predict the approximate behavior of the SFE process from the laboratory at the pilot scale for a 17-fold scale-up. Linoleic acid was the major component of the extract; palmitic, stearic and oleic acids were also detected. The economic evaluation showed that it is viable to establish a SFE plant in Brazil for SFE processing of grape seed. From the technical-economic evaluation, for SFE of grape seed at 313 K/35 MPa, an extraction time of 240 min and S/F of 6.6 produced the best relationship between yield and cost.     

Oxidative decomposition of atrazine by a Fenton-like reaction in a H2O2/ferrihydrite system

The oxidation of atrazine (ATZ) was studied in the presence of hydrogen peroxide (H(2)O(2)) and ferrihydrite at different concentrations and pHs. The rate of ATZ oxidation increased with H(2)O(2) concentration and is independent of pH ranging from 4 to 8. However, at pH 3 an increase of ten times in the rate of ATZ oxidation was observed due to the mineral dissolution. The decomposition rate of H(2)O(2) was three times higher at pH 8 than 3 and increased with increase of both H(2)O(2) and ferrihydrite concentrations. The results indicate that ferrihydrite controls oxidation of ATZ by H(2)O(2) in two different ways: (i) mineral dissolution at low pH allowing the Fenton reaction to proceed in solution and (ii) surface-mediated decomposition of H(2)O(2) producing non-reactive oxygen species in particular at higher pH. Three degradation products (desethylatrazine, desisopropylatrazine, and 2-hydroxyatrazine) were identified and corroborate with a Fenton reaction taking place in solution.