Enhancement of hematite bioreduction by natural organic matter

The effects of natural organic matter (NOM), ferrozine, and AQDS (anthraquinone-2,6-disulfonate) on the reduction of hematite (alpha-Fe2O3) by Shewanella putrefaciens CN32 were studied. It has been proposed that NOM enhances the reduction of Fe(III) by means of electron shuttling or by Fe(II) complexation. Previously both mechanisms were studied separately using "functional analogues" (AQDS for electron shuttling and ferrozine for complexation) and are presently compared with seven different NOMs. AQDS enhanced hematite reduction within the first 24 h of incubation, and this had been ascribed to electron shuttling. Most of the NOMs enhanced hematite reduction after 1 day of incubation indicating that these materials could also serve as electron shuttles. The effect of ferrozine was linear with concentration, and all of the NOMs exhibited this behavior. Fe(II) complexation only enhanced hematite reduction after sufficient Fe(II) had accumulated in the system. Fe(II) complexation appeared to alleviate a suppression of the hematite reduction rate caused by accumulation of Fe(II) in the system. Addition of Fe(II) to the hematite suspension, prior to inoculation with CN32, significantly inhibited hematite reduction and greatly diminished the effects of all of the organic materials, although some enhancement was observed due to addition of anthroquinone-2,6-disulfonate. These results demonstrate that NOM can enhance iron reduction by electron shuttling and by complexation mechanisms.     

Enhanced biodegradation of iopromide and trimethoprim in nitrifying activated sludge

Iopromide (an X-ray contrast agent) and trimethoprim (an antibacterial drug) are frequently detected pharmaceuticals in effluents of wastewater treatment plants (WWTPs) and in surface waters due to their persistence and high usage. Laboratory-scale experiments showed that a significantly higher removal rate in nitrifying activated sludge as compared to conventional activated sludge was observed for both iopromide and trimethoprim. When the activity of the nitrifying bacteria was inhibited, the percent removal of iopromide decreased from 97 to 86% while trimethoprim removal decreased from 70 to 25%. The metabolite of iopromide identified when nitrification was not inhibited was a dehydroxylated iopromide at the two side chains. However, when the nitrifying bacteria were inhibited the metabolite identified was a carboxylate, formed during the oxidation of the primary alcohol on the side chain of iopromide. These results suggest that the nitrifying bacteria are important in the observed biodegradation of iopromide in the activated sludge with higher solid retention time (SRT). Results from the laboratory-scale study were corroborated by the observed removal efficiencies in a full-scale municipal WWTP, which showed that iopromide (ranging from 0.10 to 0.27 microg/L) and trimethoprim (ranging from 0.0.08 to 0.53 microg/L) were removed more effectively in the nitrifying activate sludge which has a higher SRT (49 days) than in the conventional activated sludge (SRT of 6 days). In nitrifying activated sludge, the percent removal of iopromide in the WWTP reached 61%, while in conventional activated sludge, average removal was negligible. For trimethoprim, removal was limited to about 1% in the conventional activated sludge, while in the nitrifying activated sludge, the removal was increased to 50%.     

Thermal properties of fruit juices as a function of concentration and temperature determined using the photopyroelectric (PPE) method

The photopyroelectric (PPE) method is proposed as a new technique for thermal characterisation of fruit juices. By combining different geometries and experimental conditions, the PPE method was shown capable of providing temperature-dependent (between 0 and 70 °C) values of thermophysical parameters (thermal diffusivity, thermal effusivity, thermal conductivity and volume specific heat) for juices having different Brix index. The computer-controlled PPE cell allowed stable temperature variation rates and continuous signal acquisition. The experimental data were used to develop empirical models and hence prediction equations for all the thermal parameters. © 1999 Society of Chemical Industry     

Chemical composition,nutritive value and voluntary intake of tropical tree foliage and cocoyam in pigs

The composition of the leaves of cocoyam (Xanthosoma sagittifolium) and of two trees (Trichanthera gigantea and mulberry, Morus alba), their nutritive value in pigs and voluntary intake by pigs were determined. The average protein content ranged from 170 to 240 g kg^?1 dry matter (DM) and that of neutral detergent fibres from 218 to 398 g kg^?1 DM. The leaves are interesting sources of calcium (up to 69 g kg^?1 DM), potassium, iron and manganese. The proteins are well balanced in essential amino acids, with lysine ranging from 43 to 57 g kg^?1 proteins. The apparent faecal digestibility was determined by difference in 35 kg pigs fed a diet containing 35% leaf meal. The digestibility coefficients of DM, N and energy were, respectively, 47–57, 33–36 and 51–53%. The digestible energy value ranged from 1.674 to 2.037 kcal kg^?1 DM. The voluntary intake of Trichanthera and Xanthosoma was measured in sows weighing 100 kg on average. The intake reached 3.4 kg fresh leaves day^?1 (0.51 kg DM) and 1.0–1.1 kg dry leaf meal/day. It is concluded that low energy density is the main limiting factor of tree foliage for pig nutrition but that they are good sources of minerals and well‐balanced proteins. Copyright © 2005 Society of Chemical Industry     

Matrix effects on flavour volatiles release in dark chocolates varying in particle size distribution and fat content using GC–mass spectrometry and GC–olfactometry

Influences of matrix particle size distribution (PSD) (18, 25, 35 and 50 μm) and fat content (25%, 30% and 35%) on flavour release of dark chocolate volatiles were quantified by static headspace gas chromatography using GC–MS. Sixty-eight (68) flavour compounds were identified, comprising alcohols, aldehydes, esters, ketones, furans, pyrans, pyrazines, pyridines, pyroles, phenols, pyrones and thiozoles. From GC–olfactometry, 2-methylpropanal, 2-methylbutanal and 3-methylbutanal had chocolate notes. With cocoa/roasted/nutty notes were trimethyl-, tetramethyl-, 2,3-dimethyl-, 2,5-dimethyl-, 3(or 2),5-dimethyl-2(or 3)-ethyl- and 3,5(or 6)-diethyl-2-methylpyrazine and furfuralpyrrole. Compounds with fruity/floral notes included 3,7-dimethyl-1,6-octadien-3-ol and 5-ethenyltetrahydro-R,R,5-trimethyl-cis-2-furanmethanol. Caramel-like, sweet and honey notes were conferred by 2-phenylethanol, phenylacetaldehyde, 2-phenylethylacetate, 2,3,5-trimethyl-6-ethylpyrazine, 2-carboxaldehyde-1H-pyrrole, furancarboxaldehyde, furfuryl alcohol and 2,5-dimethyl-4-hydroxy-3(2H)furanone. There were direct relationships of fat content with 3-methylbutanal and branched pyrazines but inverse ones with 2-phenylethanol, furfuryl alcohol, methylpyrazine, phenylacetaldehyde, 2, 3, 5-trimethyl-6-ethylpyrazine and 2-carboxaldehyde-1-H-pyrrole. Particle size influenced higher alcohol, aldehyde, ester, ketone and pyrazine concentrations at all fat contents. A multivariate product space suggested flavour effects of the interacting factors.     

Antifungal activity of sourdough fermented wheat germ used as an ingredient for bread making

This study aimed at investigating the antifungal activity of sourdough fermented (Lactobacillus plantarum LB1 and Lactobacillus rossiae LB5) wheat germ (SFWG). Preliminarily, methanol and water/salt-soluble extracts from SFWG were assayed by agar diffusion towards Penicillium roqueforti DPPMAF1. As shown by hyphal radial growth rate, the water/salt-soluble extract showed the inhibition of various fungi isolated from bakeries. The antifungal activity was attributed to a mixture of organic acids and peptides which were synthesized during fermentation. Formic (24.7 mM) acid showed the highest antifungal activity. Four peptides, having similarities with well known antifungal sequences, were identified and chemically synthesized. The minimal inhibitory concentration was 2.5–15.2 mg/ml. Slices of bread made by addition of 4% (wt/wt) of freeze dried SFWG were packed in polyethylene bags and stored at room temperature. Slices did not show contamination by fungi until at least 28 days of storage and behaved as the calcium propionate (0.3%, wt/wt).     

Tannase activity by lactic acid bacteria isolated from grape must and wine

We examined a range of oenological lactic acid bacteria species and reference strains for their potential to degrade tannins. Bacterial tannase activity was checked by a spectrophotometric and a visual reading method. None of the strains belonging to the oenological species of the genus Lactobacillus, Leuconostoc, Oenococcus or Pediococcus were tannase producers, with the exception of Lactobacillus plantarum. All the L. plantarum strains analyzed were positive for tannase activity and their identities were reconfirmed by L. plantarum PCR-specific assay or by sequencing the 16S rDNA. Tannase activity could be considered an important criterion for the selection of malolactic starter cultures since it might confer advantages in the winemaking process by reducing astringency and haze in wine.     

Quantitative effect of refrigerated storage time on the enumeration of Campylobacter, Listeria, and Salmonella on artificially inoculated raw chicken meat

Active monitoring of pathogens on retail foods has been recommended and implemented in a number of developed countries. Because only a portion of retail food is contaminated with pathogens, a cost-effective and informative surveillance program at the retail level often involves a two-stage approach of initial presence-absence analysis and subsequent pathogen enumeration in any positive samples. Most-probable-number (MPN) methods are more resource intensive and therefore used only for samples considered positive by presence-absence methods. Interpretation of the results assumes that the initial bacterial count remains relatively stable between the initiation of the presence-absence analysis and the enumeration analysis. The objective of this study was to quantify the influence of 4 degrees C storage for 5 and 8 days on pathogen counts on raw chicken. The three pathogens examined were Salmonella Typhimurium, Campylobacter jejuni, and Listeria monocytogenes. No significant differences were found between treatments for Salmonella and Campylobacter. However, significant differences were observed for Listeria; counts at day 0 were lower than counts after 5 or 8 days of refrigerated storage (the maximum mean difference was less than 0.6 log units). These findings suggest that a two-stage approach could overestimate the number of Listeria cells on chicken at the time of purchase. By using an MPN analysis on the presumptive positive samples after 5 days of refrigerated storage, this difference will be reduced. These findings support the decision to reduce surveillance costs by performing a two-stage analysis for Salmonella and Campylobacter on retail chicken. This study provides direction for future sampling or surveillance programs that include enumeration of Listeria on retail food.