Characterization of aroma compounds responsible for the rosy/floral flavor in Cheddar cheese

The aroma-active compounds that contribute to the rosy/floral flavor in Cheddar cheese were characterized using both instrumental and sensory techniques. Two cheeses (>12 months old) with rosy/floral flavor and two Cheddar cheeses of similar ages without rosy/floral flavors were selected. After direct solvent extraction/solvent-assisted flavor evaporation and separation into neutral/basic and acidic fractions, samples were analyzed by gas chromatography-olfactometry with aroma extract dilution analysis. Selected compounds were quantified using internal standard methodology. Some of the intense aroma-active compounds in the neutral basic fraction of the rosy/floral cheeses included 2-phenethanol (rosy), phenylethyl acetate (rosy), and phenylacetaldehyde (rosy/floral). Quantification, threshold analysis, and sensory analysis of model cheeses confirmed that increased concentrations of phenylacetaldehyde and phenylacetic acid caused rosy/floral flavor when spiked into Cheddar cheese.     

Can We Use Zebra and Quagga Mussels for Biomonitoring Contaminants in the Niagara River?

We compared contaminants in zebra and quagga mussels (Dreissena polymorpha and Dreissena bugensis) of two different size classes from sites within the Niagara River to determine if the two species and two size classes can be used to monitor contaminants. Composite samples (i.e., at least 50 individuals) were analysed for 7 trace metals, total PCBs, selected organochlorine pesticides, chlorinated benzenes, and dioxins and furans. ANOVAs and MANOVAs showed that metal tissue concentrations varied significantly among sites, species, and size classes (P < 0.05). At sites where metal concentrations differed between species, zebra mussels had higher concentrations than quagga mussels. Similarly, larger mussels (i.e., 16–25 mm) generally had higher tissue concentrations than smaller mussels (<15 mm length). However, differences in tissue concentrations between size classes were present only for Cd, Cu and Mn and were infrequent, making these results inconclusive. For organic contaminants ANCOVAs and MANCOVAs using lipid concentration as a covariate revealed significant differences in tissue concentrations between the three sites, whereas differences between size classes were modest (P = 0.035). The ANOVA using individual parameters did not show a significant difference in tissue concentrations between the two size classes. In general, mussel tissue concentrations among stations (up to 7 stations throughout the river), were similar for Pb, Zn, Hg and Ni using data separated by species and size class. Concentrations of Cu, Mn and Cd were variable throughout the upper and lower Niagara. Tissue concentrations of α-BHC, 1,2,3 and 1,2,4 trichlorobenzene were similar in quagga mussels collected from 8 stations from the Canadian and American side of the river, whereas concentrations of total PCBs, octachlorostyrene, 1,2,3,4-tetrachlorobenzene, pentachlorobenzene and hexachlorobenzene were higher in quagga mussels from the American side of the upper river.     

The Need for Education in Developing Acceptable Air Pollution Control Strategies

The acute effects of air pollution on human health and the environment are well understood and the arguments for measures to prevent local, gross pollution are strong. Governments and the public will accept the need for controls where effects are obvious. At the broader scale where effects may be more subtle, and where the costs of abatement are high, a convincing case is necessary before acceptable solutions are adopted. An education process is needed to provide the relevant facts in an understandable form. For major air pollutants, where international agreement for control of emissions is required, effect-based instruments have proved successful in Europe. These are designed to be cost effective by offering protection to the more sensitive areas by targeting the cheapest emission controls on the sources responsible for effects. This level of complexity has demanded improved education and communication for all those involved in the decision-making process. The principles and approaches that have provided success are discussed. Attention to these is needed in the future if more stringent and costlier measures are to be agreed.     

MR properties of water in saturated soils and resulting loss of MRI signal in water content detection at 2 tesla

This paper reports a systematic MRI study at 2 tesla of 23 soils, each separately saturated with a known amount of water. The percentage of that water which could be detected using various MR methods was determined by comparison with a liquid reference sample. A pulse-acquire sequence gave a bulk detection of between 47 and 94% of the known water content of saturated soil. Also for bulk measurements, the inversion-recovery sequence used for determining T₁ values detected a range of 0.7–75% of the existing soil water. The CPMG sequence with an echo time (TE) of 1 ms used for determining the bulk T₂ values gave lower values, in the range of 0.4–66% overall. A spin-echo MRI sequence with a TE of 2.9 ms gave an even lower bulk detection, ranging from 0.2 to 57%. These low values for the detectable water content of bulk saturated soil water reflect the loss of water magnetization which occurs even during short echo time MR sequence at 2 tesla field strength. The source of the above findings was investigated by measurements of the longitudinal (T₁) and transverse (T₂) relaxation times and spectral linewidths of the soil-water protons, and by conventional analysis of soil properties. The MR parameters of critical importance to water quantification are T₂ and T₂^*, shorter values of which lead to a progressively greater loss of signal intensity for all MR protocols. Those parameters are affected by the following soil chemical and physical features: soil magnetic susceptibility, and the content of free iron oxides, clay, sand, exchangeable cations (K, Na and Ca), and organic matter. The implication of this work is that the only soil water which can be detected quantitatively at 2 tesla using a conventional spin-echo MRI protocol with echo times of 3 ms or longer is that located in the relatively large soil pores. Using the protocols investigated in this work, water in smaller pores will only be detected accurately for soils which have relatively low paramagnetic-metal impurities and/or have low clay content. Future MR studies of soil water should consider the use of other MRI protocols (e.g. for solid state), and measurement at low magnetic fields.     

Potential future effects of current levels of sulfur deposition on stream chemistry in the southern blue ridge mountains,U.S.

Using newly available regional data sets we examine the potential for future changes in stream acid neutralizing capacity (ANC) for the Southern Blue Ridge Province (SBRP) of the U.S. as related to (1) levels of S deposition, (2) retention of S within watersheds, (3) current surface water SO₄, and (4) potential historical changes in surface water chemistry. We conclude that, although (1) little change in surface water chemistry (as affected by acidic deposition) likely has occurred in the region to date, and (2) soils are currently retaining a majority of atmospherically deposited S, it is likely that marked increases in surface water SO₄ will occur. Such increases could be accompanied by significant surface water acidification (loss of ANC).     

Chemical effects of pH 3 sulphuric acid on a soil profile

Cores of podzolic soil (monolith lysimeters) were treated for 4.8 yr with 1500 mm yr^?1 of either 0.5 mM H₂SO₄ at pH 3, equivalent to 24 g S m^?2 yr^?1 (acid treated) or distilled water (controls). The acid treatment was about 37 times greater than the average annual input of H₃O⁺ from rain at the site from which the monoliths were taken. Acid treatment acidified the litter (from pH(CaCl₂)3.4 to pH(CaCl₂)2.6) and the mineral soil to a depth of 80 cm (mean pH(CaCl₂) decrease of 0.2 unit). In the litter and upper A horizon, ion-exchange reactions provided the main neutralizing mechanism, resulting in a decrease in the reserves of extractable (in 2.5 % acetic acid) Ca, Mg, and Mn of about 70 to 80 %. Dissolution of solid phase Al from hydrous oxides provided most neutralization below this depth. Al3⁺ was the principal soluble Al species throughout the profile. In the litter and upper A horizon, some of the mobilized Al³⁺ was retained on cation exchange sites resulting in an increase in exchangeable Al. Deeper in the profile, where the exchange sites were effectively saturated with Al³⁺, no increase in exchangeable Al occurred, and Al³⁺ was, therefore, available for leaching. Some reversible adsorption of SO₄ ^2?, associated with hydrous Al oxides, occurred in the Bs and C horizons. The results are discussed in relation to possible effects of acid deposition over regions of Europe and N. America.     

Sulphur distribution and metabolism in waterlogged peat

About 90% of total S in a peat profile from a valley mire was associated with organic matter, and in the anaerobic zone, most of the remaining S could be distilled as H₂S (steam-volatile H₂S). [³⁵S]SO^2?₄ was rapidly incorporated into both organic and steam-volatile H₂S pools, with preferential labelling of organic matter at the surface of the peat (? 10 cm depth) and of steam-volatile H₂S at greater depth (? 10 cm depth). Less than 2% of the steam-volatile H₂S could be accounted for as H₂S in solution in the pore water, and evidence suggesting FeS as the source of this fraction is presented. Less than 2% of the total S in the profile was present as FeS₂ or S°, and S₂O^2?₃ and S₄O^2?₆ could not be detected. Measurements of total S content of the peat and estimates of the age of the deposit indicate a rate of S accumulation of 4.76–6.06 g S m^?2yr^?1. The results are discussed in the context of the mechanisms of S transformations and uptake by other mire systems.     

The potential of using alternative pastures,forage crops and gibberellic acid to mitigate nitrous oxide emissions

Purpose

In grazed pastures, nitrous oxide (N₂O), a powerful greenhouse gas and an ozone depletion substance, is mostly emitted from animal excreta, particularly animal urine-N returned to the soil during grazing. We conducted a series of four field lysimeter and plot experiments to assess the potential of using gibberellic acid (GA) and/or alternative pastures or forage crops to mitigate N₂O emissions from outdoor dairy farming systems.

Materials and methods

Pasture and forage plants assessed in the experiments included Italian ryegrass (Lolium multiflorum L.), lucerne (Medicago sativa L.), diverse pastures (including plantain (Plantago lanceolata L.), chicory (Cichorium intybus L.), perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.)), fodder beet (Beta vulgaris L.), kale (Brassica oleracea L.), as well as the standard perennial ryegrass and white clover (RG/WC) pastures. N₂O was determined using a standard static chamber method in the field either on top of lysimeters or field plots.

Results and discussion

The results showed that the application of GA to urine-treated lysimeters with Italian ryegrass, lucerne or RG/WC pastures did not result in lower N₂O emissions. However, the use of diverse pastures which included plantain with a lower urine-N loading rate at about 500 kg N ha^?1 significantly decreased N₂O emissions by 46 % compared with standard RG/WC with a urine-N loading rate at 700 kg N ha^?1. However, when urine-N was applied at the same rates (at 500 or 700 kg N ha^?1), the N₂O emissions were similar between the diverse and the standard RG/WC pastures. This would indicate that it is the N-loading rate in the urine from the different pastures that determines the N₂O emissions from different pastures or forages, rather than the plants per se. The N₂O emissions from cow urine from fodder beet were 39 % lower than from kale with the same urine-N application rate (300 kg N ha^?1).

Conclusions

These results suggest that N₂O emissions can potentially be reduced by incorporating diverse pastures and fodder beet into the grazed pasture farm system. Further studies on possible mechanisms for the lower N₂O emissions from the different pastures or forages would be useful.

     

Activated Carbon Produced from Waste Wood Pallets: Adsorption of Three Classes of Dyes

Activated carbon was derived from waste wood pallets in Hong Kong via phosphoric acid activation and applied to adsorption of basic dye (methylene blue), acid dyes (acid blue 25 and acid red 151), and reactive dye (reactive red 23). The results showed that respective adjustment in phosphoric acid concentration, impregnation ratio, activation temperature, and activation time could maximize the surface area and pore volume of activated carbon. An increase of impregnation ratio or activation temperature significantly influenced the pore size distribution by expanding the porous structure and creating more macropores than micropores. The characterization of the carbon surface chemistry using Fourier-transform infrared (FTIR) spectroscopy, however, revealed a decrease in the amount of several functional groups with increasing activation temperature. The physical properties (surface area and pore volume) of the wood waste-derived activated carbon (using 36% phosphoric acid with an impregnation ratio of 1.5 at an activation temperature of 550°C for 1.5 h) were comparable to those of commercial activated carbon (Calgon F400). The contrasting pH effects on the adsorption of different classes of dyes signified the importance of both electrostatic interaction and chemical adsorption, which correlated to pH-dependent dissociation of surface functional groups. It is noteworthy that the physical properties of activated carbon were insufficient to account for the observed dye adsorption behavior, whereas the surface chemistry of activated carbon and the nature and chemical structure of dyes were more important. The fast kinetics and high capacity of dye adsorption of wood waste-derived activated carbon suggest that production of activated carbon from different types of wood waste should merit further investigation.