Effects of plant population on soil structure,soil moisture depletion and on yield of cassava (Manihot esculentd) on an Ultisol in Southeast Nigeria

The effects of four cassava populations (8, 10, 13 and 20 × 10³ plants per ha^?1) on soil physical properties, moisture retention characteristics, moisture potential profiles and moisture depletion patterns were compared with uncropped plots receiving no cultivation of an Ultisol in the humid region in eastern Nigeria. The growing of cassava decreased the bulk density of 0–10 cm depth by 17% in comparison with the uncultivated soil (1.53 Mg m^?3). The bulk density of the 10–20 cm depth was higher for the cropped than the uncropped control plots. The moisture retention below a suction of pF 2.4 for 0–10 cm depth was less for the uncultivated control than for soil growing cassava. The reverse was found in moisture retention characteristics of the 20–40 cm depth especially for low suction ranges of pF below 0.8. The 0–10 cm soil layer of uncropped control dried more rapidly than the cropped soil. Below 10 cm, however, cassava depleted moisture reserves more rapidly than in uncropped control. The effect of plant population on soil moisture depletion was more conspicuous within than between rows. Significant differences in water flux and in water uptake from different horizons were observed among various population densities. The total water loss was the highest for the least plant population for the between-row zone, and for the highest population for the within-row zone. Plant population had no effect on tuber and stalk yield.     

Biocontrol of Salmonella Typhimurium in RTE foods with the virulent bacteriophage FO1-E2

Antimicrobial agents can be incorporated into edible films to provide microbiological stability, since films can be used as carriers of a variety of additives to extend product shelf life and reduce the risk of microbial growth on food surfaces. Addition of antimicrobial agents to edible films offers advantages such as the use of small antimicrobial concentrations and low diffusion rates. The aim of this study was to evaluate inhibition by vapor contact of Aspergillus niger and Penicillium digitatum by selected concentrations of Mexican oregano (Lippia berlandieri Schauer), cinnamon (Cinnamomum verum) or lemongrass (Cymbopogon citratus) essential oils (EOs) added to amaranth, chitosan, or starch edible films. Essential oils were characterized by gas chromatography-mass spectrometry (GC/MS) analysis. Amaranth, chitosan and starch edible films were formulated with essential oil concentrations of 0.00, 0.25, 0.50, 0.75, 1.00, 2.00, or 4.00%. Antifungal activity was evaluated by determining the mold radial growth on agar media inoculated with A. niger and P. digitatum after exposure to vapors arising from essential oils added to amaranth, chitosan or starch films using the inverted lid technique. The modified Gompertz model adequately described mold growth curves (mean coefficient of determination 0.991 ± 0.05). Chitosan films exhibited better antifungal effectiveness (inhibition of A. niger with 0.25% of Mexican oregano and cinnamon EO; inhibition of P. digitatum with 0.50% EOs) than amaranth films (2.00 and 4.00% of cinnamon and Mexican oregano EO were needed to inhibit the studied molds, respectively). For chitosan and amaranth films a significant increase (p<0.05) of lag phase was observed among film concentrations while a significant decrease (p<0.05) of maximum specific growth was determined. Chitosan edible films incorporating Mexican oregano or cinnamon essential oil could improve the quality of foods by the action of the volatile compounds on surface growth of molds.     

Survival of coliform bacteria in static compost piles of dairy waste solids intended for freestall bedding

Dairy waste solids separated from a slurry by a centrifugal separator were composted in 12 static piles. Seven of the compost piles were naturally aerated, and five were aerated by a fan that forced air through the piles of solids. The natural aeration process aged the manure solids in an unconfined pile. The fan in the forced aeration process forced air into a perforated plenum beneath the compost piles. Dairy waste solids in each compost pile were heated into the thermophilic temperature range and generally composted well. At most sampling points, coliform bacteria declined to low or undetectable numbers early in the composting period. However, as the composting process proceeded, bacterial numbers increased to approximately those present in raw dairy waste solids. Findings of this study suggest that composting offers little benefit toward net reduction in coliform bacterial numbers in dairy waste solids.     

Aminoglycoside-resistant Streptococcus and Enterococcus species isolated from bovine mammary secretions.

A total of 117 isolates representing four Streptococcus species and 20 isolates representing two Enterococcus species from bovine mammary secretions were examined for resistance to streptomycin, kanamycin, and gentamicin. Resistance to streptomycin (85.4%) was most prevalent, followed by kanamycin (19%) and gentamicin (2.2%). Minimum inhibitory concentration of streptomycin for most organisms examined ranged from 16 to 250 micrograms/ml. For kanamycin, the minimum inhibitory concentration for most organisms was .5 to 62.5 micrograms/ml. Minimum inhibitory concentration for gentamicin was lower than for kanamycin. Two strains each of Streptococcus uberis and Enterococcus faecalis had minimum inhibitory concentration for streptomycin of greater than 2000 micrograms/ml, and two strains of E. faecalis had similar minimum inhibitory concentration for kanamycin. The minimum bactericidal concentration for all organisms was one to four times higher than minimum inhibitory concentration. None of the organisms evaluated was found to carry plasmids. Transfer of antibiotic resistance in plasmid-free strains was not achieved by mobilization with the aid of plasmid pAD1, indicating the absence of conjugative transposons. These data suggest that expression of aminoglycoside resistance of Streptococcus and Enterococcus species of bovine origin is likely due to factors other than plasmids or conjugative transposons.     

In vitro binding of zearalenone to different adsorbents

Zearalenone (ZEA) is a potent estrogenic metabolite produced by some Fusarium species. No treatment has been successfully employed to get rid of the ZEA contained in foods. This study was conducted to evaluate the ability (adsorptive power) of five adsorbents--activated carbon, bentonite, talc, sandstone, and calcium sulfate--to trap ZEA in vitro. Activated carbon was the best adsorbent, binding 100% ZEA (pH 3 and 7.3) at 0.1, 0.25, 0.5, and 1% dose levels. Bentonite, talc,and calcium sulfate were less efficient than activated carbon but still could bind ZEA to some extent. On the other hand, sandstone was inactive in the experimental conditions employed. Our results indicate that activated carbon could be a good candidate for detoxification of ZEA present in foods.     

Acidified sodium chlorite treatment for inhibition of Listeria monocytogenes growth on the surface of cooked roast beef

The effects of acidified sodium chlorite (ASC) against Listeria monocytogenes on the surface of cooked roast beef were investigated. L. monocytogenes, strain V7, serotype 1/2a, was inoculated at numbers of 6.0 log CFU/g onto 5-g cubes of cooked regular or spicy roast beef. The samples were allowed to air dry for 1 h. The cooked roast beef samples were dipped into ASC or sprayed with ASC solutions of 250, 500, 750, or 1,000 ppm, then placed in bags with or without a vacuum and refrigerated at 4 degrees C. L. monocytogenes counts were determined after 0, 7, 14, 21, and 28 days of storage by spread plating roast beef samples onto Oxford agar plates that were incubated at 37 degrees C for 48 h. At day 28, the number of L. monocytogenes on the > or = 500 ppm ASC-treated spicy roast beef samples had count reductions that were >4.0 log CFU/g, whereas the same concentrations of ASC-treated regular roast beef samples had approximately a 2.5 log CFU/g reduction in L. monocytogenes counts when compared with the untreated samples. No significant differences (P > 0.05) were observed in L. monocytogenes counts between the vacuum- or nonvacuum-packaged ASC-treated cooked roast beef samples. Sensory evaluation showed no significant differences (P > 0.05) between ASC-treated and untreated roast beef. ASC can be used as a processing aid in the form of a dip or spray treatment to control L. monocytogenes on the surface of cooked roast beef.     

Validation and application of an LC-MS/MS method for the determination of cyclic oligomers originating from polyamide 6 and polyamide 66 in food simulant

Polyamides (PAs) are used in the production of various food contact materials (FCMs) and articles such as kitchen utensils and packaging material. Cyclic oligomers have been identified as potential migrants from PA. This study describes the development, validation and application of a multi-oligomer analytical method based on LC-ESI-MS/MS for the identification and quantification of eight cyclic oligomers of PA 6 and four PA 66 migrating from FCMs into food simulant B (3% acetic acid) and beverages. It was proved that doubly charged precursor ions of the cyclic PA 6 and PA 66 oligomers above a mass of 500 Da are formed during the ionisation process of the electrospray technique used. Direct injection of a diluted food simulant into the LC-ESI-MS/MS system after migration makes the validated method a valuable tool for investigating migration of cyclic PA oligomers. The validation results demonstrate that the multi-oligomer method is applicable for the analysis of cyclic PA 6 and PA 66 oligomers in food simulant B. For all investigated cyclic PA oligomers, detection limits were in the range of 0.1–1.1 µg/l. Linearity (r² ≥ 0.99), trueness values between 91% and 122%, and intra-day (RSD_r < 10%) and inter-day precision (RSD_R < 19%) were determined and satisfied validation criteria set out by the European Reference Laboratory for FCMs. The method was extended to tap water and tea. Finally, the multi-oligomer method was successfully applied to determine cyclic PA oligomers in migration solutions originating from different PA FCMs. In all migration solutions, concentrations of cyclic PA oligomers were determined above the LOQ. A preliminary risk assessment based on in silico tools was performed. The results demonstrate the urgent need for toxicological data that would facilitate the evaluation of the health risk of cyclic PA oligomers.     

Esterolytic and lipolytic activities of lactic acid bacteria isolated from ewe's milk and cheese

In the present work, we report on the esterase and lipase activities of lactic acid bacteria representing the genera Lactococcus, Leuconostoc, Lactobacillus, and Enterococcus isolated from ewe's milk and cheeses. Esterase activity was studied using alpha- and beta-naphthyl derivatives of 2 to 12 carbon atoms and postelectrophoretic detection. The lactic acid bacteria evaluated had intracellular esterase activities, which preferentially degraded the alpha- and beta-naphthyl derivatives of 2 to 6 carbon atoms. By studying postelectrophoretic patterns, it was found that some strains presented more than one esterase. Lactobacillus plantarum O236 showed four enzymes that hydrolyze carboxyl ester linkages with different specificity. Lipase activity was studied in intracellular and extracellular fractions using tributyrin, tricaprylin, triolein, and milk fat as substrates. The intracellular and extracellular fractions of Leuconostoc mesenteroides O257, Lactobacillus plantarum O236, and Lactobacillus acidophilus O177 were able to hydrolyze tributyrin. L. plantarum O186, L. acidophilus O252, Enterococcus faecium O174 and O426, and Enterococcus faecalis Ov409 showed lipase activity associated with the intracellular fraction on tributyrin. Lactococcus lactis O233, L. plantarum O155, and Lactobacillus casei O190 did not hydrolyze triglycerides. Not all strains that showed esterase activity exhibited high activity on triglycerides. Esterase and lipase activities were species- and strain-specific. Wide variations in activity between strains highlight the need for selecting appropriate starters to produce enzyme-modified cheese as well as accelerated ripened cheese.     

Storage of NO2 on BaO/TiO2 and the influence of NO

The influence of NO on the adsorption and desorption of NO₂ on BaO/TiO₂ has been studied under lean conditions. The adsorption of NO₂ involves the disproportionation of NO₂ into an adsorbed nitrate species and NO released to the gas phase with a 3:1 ratio,

BaO+3NO₂→NO+Ba(NO₃)₂.

Three different nitrate species form on the catalyst: surface nitrates on the TiO₂ support, surface nitrates on BaO, and bulk barium nitrate. The stability of the three species in different gas feeds was investigated by temperature-programmed desorption (TPD).

The reverse reaction of the NO₂ disproportionation has also been observed. If NO is added to the feed, nitrates previously formed on the sorbent will decompose into NO₂. Therefore, the above chemical equation should be considered as an equilibrium reaction. Applying this finding to the NO_x storage and reduction catalyst means that NO probably reacts with the previously formed nitrates yielding NO₂ as an intermediate product. This NO₂ is subsequently reduced by the reducing agents (hydrocarbons and CO) present during the regeneration period.     

Self‐Healing Rubbers Based on NBR Blends with Hyperbranched Polyethylenimines

Hyperbranched PEI and urea‐functionalized PEI amphiphiles are employed as additives in NBR compounding. Polarity design governing phase separation, PEI migration and PEI‐mediated self‐healing of NBR is demonstrated. The compatibility of PEI and NBR decreases with increasing molecular weight of PEI and with decreasing degree of substitution. Microphase‐separated NBR/PEI blends are prepared with varying PEI molecular architectures. Thermal self‐healing of NBR/PEI is monitored by applying tests combining crack initiation with annealing under compression. All PEI additives show complete crack‐healing upon annealing at 100 °C for 12 h. In contrast to neat NBR, the NBR/PEI‐2 blend afforded a self‐healing efficiency of 44% after cutting and re‐joining by compression and annealing.