Anticorrosives, encapsulates, catalytic supports and other novel nanostructured materials

A phenolic-formaldehydic resin (PFR) of the Novolac-type and modified through the attachment of carboxylic end groups (MPR), is used to tailor the morphological and optical properties of sol–gel synthesized silica materials. Silica microparticles are produced from alkoxide precursors in the presence of PFR or MPR resins, leading to a final material consisting of SiO₂ globules entangled inside a polymerized resin matrix. Under appropriate experimental conditions, chemical bonds can be established between the SiO₂ silanol surface groups and the MPR carboxylic chains, to render SiO₂/MPR core-shell-type compounds. The presence of PFR or MPR resins during the sol–gel production of silica microspheres allows to control: (i) the sizes of final SiO₂ particles and (ii) the transparency or opacity properties of the final hybrid products. In this way, either opaque or transparent solid substrates can be obtained, depending on the amounts of reactants used to prepare the hybrid specimens. Solid MPR and SiO₂/MPR samples were characterized by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy to determine chemical and textural properties of the hybrid substrates. Under appropriate experimental conditions, chemical bonds could be established between the SiO₂ silanol surface groups and the MPR carboxylic chains, to render SiO₂/MPR core-shell-type compounds.     

EVALUATION OF FLUORESCENT IN SITU HYBRIDIZATION (FISH) AS A RAPID SCREENING METHOD FOR DETECTION OF SALMONELLA IN TONSILS OF SLAUGHTERED PIGS FOR CONSUMPTION: A COMPARISON WITH CONVENTIONAL CULTURE METHOD

The pork tonsils are an important carrier of Salmonella, which could be involved in the contamination of pork products during the slaughter process. This paper reports a 23S rRNA fluorescent in situ hybridization (FISH) method used as a rapid screening tool for Salmonella detection in tonsils of slaughtered pigs and its comparison with the conventional culture method. As a rapid screening method, the FISH technique would reduce the high volume of negative samples that are routinely analyzed, indicating presumptive positive samples in a real and practical time. The use of a Sal3 probe allowed the rapid (7 h) Salmonella detection in 16 (34%) of 47 naturally contaminated tonsils, without pre‐enrichment. Salmonella was isolated by the culture method in six samples that were also FISH‐positive samples, and FISH failed to identify only one of the culture‐positive samples. The results indicate the potential of this technique as a rapid screening method for detecting Salmonella in tonsils from pork slaughtered for consumption.     

Supercritical CO2 Conditions Affecting Extraction of Lipid and Cholesterol from Ground Beef

Ground beef was extracted by supercritical CO₂ (SC-CO₂) with pressure ranging from 103-310 bar at 30-50°C. Higher pressure was needed to increase yield of extracted lipid. The profile of cholesterol content for the fractionated lipid extracted at 172 bar or 310 bar was generally lower in the initial stage of extraction and increased with CO₂ used. DSC thermograms indicated that, depending upon extraction conditions, the distribution of lipid components of fractionated samples either shifted toward higher melting temperatures or concentrated those lipids melting between 5-25°C.     

LIPOPEROXIDATION AND ANTIOXIDANT ENZYMES OF REFRIGERATED PERSIAN LIMES (CITRUS LATIFOLIA TANAKA) AS INFLUENCED BY A PRESTORAGE HOT TREATMENT

Effectiveness of a hot water dip conditioning (3 min, 53C) to prevent chilling injury was evaluated with Persian lime (Citrus latifolia Tanaka) fruits stored at 4, 8, 13 and 25C and 80% RH. Conditioning caused a significant increase in peroxidase and superoxide dismutase activities and lipoperoxidation levels in the flavedo of fruits immediately after treatment. During storage enzyme activities diminished until they reached control levels. Conditioned limes kept at 25C maintained higher lipoperoxidation levels than those stored at refrigerated temperatures during all storage periods. Lipoperoxidation decreased slowly in refrigerated fruits until they reached similar levels to control fruits. Chilling injury was observed at 4 and 8C, however, it showed the highest levels in heated fruits. Therefore, conditioning by heat did not act as a protective treatment against chilling injury of Persian limes, possibly because it was not able to sustain the increased antioxidant system during the entire storage period., 27 December 2003     

Suitability of whey and buttermilk for the growth and frozen storage of probiotic lactobacilli

The growth of six probiotic commercial strains of lactobacilli was assessed in reconstituted dried whey and buttermilk supplemented with yeast extract, meat peptone, soy peptone, tryptone or casein acid hydrolysate at 0.3%, 0.6% or 1%. The addition of 1% glucose was also tested. Growth and acidification kinetics were determined at 37°C using MRS broth and a commercial culture medium as references. The suitability of whey and buttermilk as cryoprotectants at –20°C and –70°C was also assessed. Whey and buttermilk with 0.3% yeast extract were chosen for the growth of probiotic lactobacilli, since no satisfactory growth was observed without an external nitrogen source, whereas glucose did not improve the growth of any of the strains assayed. In general, buttermilk performed as satisfactorily as the reference media. The effectiveness of these media as cryoprotectants was strain dependent: skimmed milk and whey were the most suitable ones, especially for long-term storage at –20°C. However, at –70°C, no significant differences were observed between the culture media assessed. The use of whey or buttermilk as culture media for the production of probiotic lactic acid bacteria and for their cryopreservation implies a novel use of these low-cost products, offering an alternative way of utilizing the by-products of the dairy industry, helping to minimize their negative impact on the environment.     

DISCREPANCIES AND CONSISTENCIES IN THE SUBJECTIVE RATINGS OF WINE-TASTING COMMITTEES

Tasting committees issuing subjective scores carry out the evaluation of wines, as for many other food products. Since highly qualified experts form wine‐tasting committees, the reliability of the scores is not generally questioned. Nevertheless, statistical methods can be applied to assess the work of tasters from the point of view of concordance. Agreement degree may be used as a measurement of the reliability of subjective rating. In order to evaluate both the extent of agreement as well as the circumstances that produce disagreement, this paper examines the subjective scores assigned to white wines awarded the Rias Baixas (Spain) denomination of origin certificate using statistical analysis. It will be seen that agreement depends significantly on the variability in scoring. A statistical method is proposed, which permits an appraisal, in terms of consistency and reliability, of the committees that evaluate wines for quality and authenticity.     

Wear behaviour of an aluminium matrix composite

The wear behaviour of a composite material consisting in AS12UNG alloy reinforced with 15% short fibres of alumina has been studied. The material composition and the wear test conditions were defined in order to evaluate the potential performance of automotive pistons produced with such composite composition. As initially expected, the results indicate that an increase in the sliding velocity lead to higher wear rates in the stationary stages, and higher applied loads also induced acceleration in the wear process. Also, reciprocating sliding movement is clearly more damaging than the circular. However, results have shown that wear rates at 150 °C are lower than those recorded at room temperature representing a promising result for the use of this material in components that operate in this condition. This advantageous behaviour is lost at temperatures near to 300 °C, when a marked increase in the wear rate and a signification contribution of adhesive wear were observed.     

METACHROMATIC EFFECT IN HOMOLOGOUS GROUPS OF WHEAT, BARLEY AND RYE PROLAMINS

The metachromatic behavior of wheat, barley and rye prolamins, separated by polyacrylamide gel electrophoresis (PAGE) and staining with Coomassie Brilliant Blue R-250, is described. Metachromasia was detected both visually and by double beam densitometric analysis of sodium dodecyl sulfate-PAGE and acidic-PAGE (A-PAGE) at pH 3.1. Differential readings were recorded at 525 nm, with reference at 625 nm. Metachromatic components were found in the homologous groups, (a) S-poor prolamins: ω-gliadins, C-hordeins, ω-secalins and (b) high molecular weight (HMW)-prolamins: HMW-glutenins, D-hordeins and HMW-secalins, in wheat, barley and rye, respectively. In contrast, proteins having this characteistic have not been found in oat.     

Electrochemical Regeneration of Activated Carbon Saturated with Toluene

The electrochemical regeneration of an activated carbon, previously saturated with toluene by gas phase adsorption, was studied. Cathodic and anodic regeneration methods were analyzed using a small batch electrochemical cell. In both cases, a stripping efficiency close to 100% was obtained under appropriate conditions of potential, current, and time of electrolysis. Successive loading and regeneration cycles of the activated carbon were performed under cathodic conditions without loss of the adsorption properties of the activated carbon, thus achieving a high regeneration efficiency (close to 99%). This electrochemical method is very effective for regeneration of activated carbon compared to conventional thermal regeneration as it does not modify the porous texture of the material.