Influence of lambda-carrageenan on the release of systematic series of volatile flavor compounds from viscous food model systems     

Bylaite E  Ilgunaite Z  Meyer AS  Adler-Nissen J 《Journal of agricultural and food chemistry》2004,52(11):3542-3549

The effect of lambda-carrageenan addition level (0.1, 0.25, 0.4, and 0.5% w/w) and viscosity on the release of systematic series of aroma compounds (aldehydes, esters, ketones, and alcohols) was studied in thickened viscous solutions containing lambda-carrageenan and 10 wt % of sucrose. Air-liquid partition coefficients K (37 degrees C) of a total of 43 aroma compounds were determined in pure water and in the lambda-carrageenan solutions by static headspace gas chromatography. Mass transfer of the aroma compounds in water and in the thickened lambda-carrageenan solutions which had a wide viscosity range was assessed by dynamic headspace gas chromatography. K (37 degrees C) increased as the carbon chain increased within each homologous series. Esters exhibited the highest volatility, followed by aldehydes, ketones, and alcohols. Under equilibrium, no overall effect of lambda-carrageenan was found, except with the most hydrophobic compounds. Analysis of flavor release under nonequilibrium conditions revealed a suppressing effect of lambda-carrageenan on the release rates of aroma compounds, and the extent of decrease in release rates was dependent on the physicochemical characteristics of the aroma compounds, with the largest effect for the most volatile compounds. However, none of the effects was of a magnitude similar to the obtained changes in the macroscopic viscosity, and the suppressing effects are therefore attributable to the thickener and not the physical properties of the increasingly viscous systems.  相似文献   

Aluminium and uptake of base cations by tree roots: A critique of the model proposed by Sverdrup et al.     

Peter Högberg  Paul Jensén 《Water, air, and soil pollution》1994,75(1-2):121-125

Sverdrupet al. (1992) proposed a model intended to evaluate effects of soil solution (Ca²⁺+Mg²⁺/Al³⁺ ratios on the uptake of Ca²⁺ and Mg²⁺ (here called base cations=BC) by tree roots. They considered the adsorption of BC on exchange sites on root surfaces to be a major step, and the competition between Al³⁺ and BC for exchange sites on roots to be crucial. Although this may certainly affect the rates of uptake, it will not exclude base cations from entering the root cells through ion channels or by carriers. Above all, the model overlooks important gradients in the rhizosphere, e.g. pH-gradients and root exudates, which have profound influences on the speciation of Al. One should instead consider modifying existing models accounting for processes in a buffered soil medium and handling gradients in the rhizosphere (e.g. Nye and Tinker, 1977). This would also require considerations on mycorrhizas and possible changes in the capacity for uptake of certain ions, which could be induced by deficiencies.  相似文献   

Die Verlagerung physikalisch wechselwirkender Ionen in Böden - Modellentwicklung und -kalibrierung -     

Jens Utermann  Jrg Richter 《植物养料与土壤学杂志》1988,151(3):165-170

Leaching of physically interactive ions in soils - Model development and calibration - A deterministic approach is presented in order to describe vertical leaching of physically interactive cations (K⁺, Na⁺, Ca²⁺, Mg²⁺). Model calibration with undisturbed and disturbed Eutric Gleysol columns under quasi-stationary conditions shows good agreement between measured and simulated concentration profiles. Interaction with the soil matrix is measured on the base of exchange isotherms (Beckett, 1964). Gapon coefficients are derived directly from the slope of the Q/I relationships. In the case of non-linearity of the exchange isotherms it is necessary to use Gapon coefficients, variable in time and space. KCl application induces K⁺ fixation in every case, which can be described by a simple diffusion approach. Leaching phenomena in one of the undisturbed columns can only be explained on the base of a dual pore system.  相似文献   

Fluorescence of muscle and connective tissue from cod and salmon   总被引：1，自引：0，他引：1  

Andersen CM  Wold JP 《Journal of agricultural and food chemistry》2003,51(2):470-476

Autofluorescence of salmon and cod muscle was measured and compared with autofluorescence of collagen type I and type V. Similarities between fluorescence of fish muscle and collagen were found in that the same peaks were obtained around 390, 430, and 480 nm. These similarities are supported by principal component analyses. Texture and gaping score were predicted from the fluorescence spectra by partial least-squares regression. However, the predictions did not perform well. Relating fluorescence to the gaping score gave a prediction error of 0.91 and a correlation of 0.43 when measuring gaping on a scale from 0 to 5. There was no relation between texture and fluorescence spectra. Fluorescence of fish muscle could be related to the storage time. However, this relation seemed not to be induced by changes in collagen.  相似文献   

Analysis of products of animal origin in feeds by determination of carnosine and related dipeptides by high-performance liquid chromatography   总被引：5，自引：0，他引：5  

Schönherr J 《Journal of agricultural and food chemistry》2002,50(7):1945-1950

Products of animal origin such as meat meal were commonly used as sources of protein and amino acids for the production of compound feeds. Because the feeding of such products is prohibited in Germany, the official feedstuff control of the government must evaluate feeds for the forbidden use of products of animal origin. Microscope examination is the official method to prove animal-originated adulterations of feeds. This paper proposes a high-performance liquid chromatography method for the determination of the dipeptide carnosine and related dipeptides (anserine and balenine) and shows the dependence of the contents of anserine, balenine, and carnosine in compound feeds on the content of meat meal in feeds. The presented method can complete and confirm the result of the microscopic method for evidence of components of animal origin in feeds.  相似文献   

Effects of Foliar Fertilization on Incidence of Berry Shrivel and Bunch Stem Necrosis in Vitis vinifera L. CVS ‘Pinot Blanc’ and ‘Zweigelt’     

Kristina Bachteler  Monika Riedel  Nikolaus Merkt  Wolfgang Schies  Jutta Fröhlin  Jens Wünsche 《Journal of plant nutrition》2015,38(6):839-853

Berry shrivel and bunch stem necrosis are the economically most important physiological disorders of grapevine. The nutritional status of the plant is considered as one of the main elicitors for the occurrence of these disorders. For foliar fertilization trials, two vineyards that had previously been affected by both diseases were selected in Southwest Germany, one with the variety ‘Zweigelt’ and one with Pinot Blanc. By the use of potassium, magnesium, and calcium foliar fertilizers, a rapid increase of different nutrients in the plants should be caused and the effects on the diseases observed. In 2010, no significant differences in the fertilization treatments were found for both varieties. In ‘Pinot Blanc’, significantly more berries were affected by berry shrivel in 2011 in plots treated with calcium fertilizer compared to those treated with potassium and magnesium. Plots with magnesium fertilizer showed significantly less berries affected by berry shrivel than the untreated control.  相似文献   

A comparison of two methods for the isolation of free and occluded particulate organic matter     

Angelika Klbl  Jens Leifeld  Ingrid Kgel‐Knabner 《植物养料与土壤学杂志》2005,168(5):660-667

Various methods exist for the isolation of particulate organic matter (POM), one of the soil‐organic‐matter (SOM) fractions reacting most sensitive on land‐use or soil‐management changes. A combination of density separation and ultrasonic treatment allows to isolate two types of POM: (1) free POM and (2) POM occluded in soil aggregates. POM fractions are closely linked to their biochemical function for the formation and stabilization of aggregates, therefore methods using different aggregate sizes may result in different POM fractions isolated. We evaluated two physical fractionation procedures to reveal whether they yield different POM fractions with respect to amount and composition, using grassland and arable soils with sandy‐loam to sandy–clay‐loam texture and thus low macroaggregate stability. Method I used air‐dried aggregates of <2.0 mm size and a low‐energy sonication for aggregate disruption, method II used field‐moist aggregates <6.3 mm and a high‐energy–sonication procedure for aggregate disruption. POM fractions were analyzed by elemental analysis (C, N) and CPMAS ¹³C‐NMR spectroscopy. With both methods, about similar proportions of the SOM are isolated as free or occluded POM, respectively. The free‐ and occluded‐POM fractions obtained with method I are also rather similar in C and N concentration and composition as shown by ¹³C‐NMR spectroscopy. Method II isolates a free‐ and occluded‐POM fraction with significantly different C and N concentrations. NMR spectra revealed significant differences in the chemical composition of both fractions from method II, with the occluded POM having lower amounts of O‐alkyl C and higher amounts of aryl C and alkyl C than the free POM. Due to the use of larger, field‐moist aggregates with minimized sample pretreatment, two distinctly different POM fractions are isolated with method II, likely to be more closely linked to their biochemical function for the formation and stabilization of aggregates. High‐energy sonication as in method II also disrupts small microaggregates <63 µm and releases fine intraaggregate POM. This fraction seems to be a significant component of occluded POM, that allows a differentiation between free and occluded POM in sandy soils with significant microaggregation. It can be concluded, that microaggregation in arable soils with sandy texture is responsible for the storage of a more degraded occluded POM, that conversely supports the stabilization of fine microaggregates.  相似文献   

Colluvisols under cultivation in Schleswig-Holstein. 1. Genesis,definition and geo-ecological significance     

Lothar Beyer  Carsten Köbbemann  Jens Finnern  Dirk Elsner  Uwe Schleuß 《植物养料与土壤学杂志》1993,156(3):197-202

In Schleswig-Holstein, F.R.G., two typical soil associations from loamy boulder marl and loamy pleistocene sands were mapped and ecologically characterized in order to show the necessity of an adequate classification of Colluvic Cumulic Anthrosols (Colluvisols). More than 50% of the original soils have been altered by erosion. The depth of the colluvic wM horizon ranges between 10 cm and more than 100 cm. The amounts of soil organic matter and plant available nutrients are much higher in the Colluvisols than in the haplic soils. Soil classification does not deal with all these aspects with regard to mapping of colluvic soils. In the German soil classification adequate and ecologically significant definitions and instructions of the nomenclature of colluvic soils are not available. Therefore, a proposal is presented to classify colluvic soils. In addition the threshold value of 0.6% soil organic matter in sandy parent material is too low in order to distinguish a Bv from a M horizon; 1.0% would be a more acceptable value. It would be necessary to investigate yield on erodic, non-erodic and colluvic soils in order to determine the effect of erosion and accumulation on crop yield.  相似文献   

Harvest regimen optimization and essential oil production in five tansy (Tanacetum vulgare L.) genotypes under a northern climate     

Dragland S  Rohloff J  Mordal R  Iversen TH 《Journal of agricultural and food chemistry》2005,53(12):4946-4953

Tansy (Tanacetum vulgare L.) was cultivated at the Norwegian Crop Research Institute at the Apelsvoll Research Centre, Division Kise, in the period from 2000 to 2001. The study focused on different harvesting regimens for high biomass production and essential oil (EO) yield and quality. Two tansy genotypes from Canada (Richters and Goldsticks) and three Norwegian genotypes (Steinvikholmen, Alvdal, and Brumunddal) were studied. The Canadian genotypes reached a height of 130-145 cm and showed a higher dry weight of aerial plant parts compared to the Norwegian plants in 2000. Similar oil yields could be observed for the Canadian types and genotype Steinvikholmen in the range of 30.8-34.6 L/ha when the plants were harvested twice during budding and before flowering after regrowth (year 2001). In contrast, single harvesting at the full bloom stage resulted in higher oil yields, between 42.1 and 44.5 L/ha (Canadian genotypes), whereas 21.0-38.4 L/ha was obtained from the Norwegian types. Tansy genotypes could be grouped into the following chemotypes: the mixed chemotypes Steinvikholmen (thujone-camphor), Alvdal (thujone-camphor-borneol), Goldsticks (thujone-camphor-chrysanthenyl type), and Brumunddal (thujone-camphor-1,8-cineole-bornyl acetate/borneol-alpha-terpineol) and the distinct chemotype Richters, with average concentrations of (E)-chrysanthenyl acetate >40% in both leaf and flower EO.  相似文献   

A retrospective study on salmonella infection in Danish broiler flocks     

ystein Angen  Marianne N. Skov  Mariann Chril  Jens F. Agger  Magne Bisgaard 《Preventive veterinary medicine》1996,26(3-4):223-237

A retrospective longitudinal study was conducted to identify risk factors associated with Salmonella enterica infection in Danish broiler production. The study was based on information in the antemortem database (AM database) where data were available for all broiler flocks slaughtered over the 2-year period from 1992 to 1993 in Denmark. The AM database contains information collected by the ante-mortem veterinarians, from the slaughterhouses, and from the salmonella examinations carried out at the National Veterinary Laboratory. The epidemiological unit was the individual broiler flock. The salmonella status of the flock was determined by examining the caecal tonsils from 16 3-week-old chickens from each flock. This procedure would detect a salmonella-infected flock, with a probability above 95%, if the prevalence is above 20%. Furthermore, the structure and quality of the collected data have been evaluated.

Fourteen variables were selected for analysis by multivariable logistic regression. An increased risk of salmonella infection in the broiler flocks was associated with the biggest hatcheries and feedmill, with an increasing number of houses on the farm, if the preceding flock was infected, and if the flock was reared in the autumn. Additionally, the main variables of the model were analysed by including a random effect at the house level. This resulted only in minor changes of the parameter estimates.  相似文献