Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Language
Year
  • 1
    Language: English
    In: Analytical and Bioanalytical Chemistry, 2012, Vol.403(10), p.3031(10)
    Description: The substitution of ewe's and goat's milk for cheaper cow's milk is still a fraudulent practice in the dairy industry. Moreover, soy-based products (e.g., soy milk, yoghurt) have to be checked for cow's milk as they are an alternative for people suffering from an allergy against bovine milk proteins. This work reports the evaluation of different protein-based electrophoretic methods and DNA-based techniques for the qualitative detection as well as the quantitative determination of cow's milk percentage in dairy and soy milk products. Isoelectric focusing (IEF) of [gamma]-caseins using an optimized pH gradient was appropriate not only for the detection of cow's milk, but also for an estimation of cow's milk percentage in mixed-milk cheese varieties. Urea-polyacrylamide gel electrophoresis (PAGE) proved the method of choice to detect cow's milk in soy milk products, whereas IEF and SDS-PAGE of proteins were not applicable due to false-positive results. Polymerase chain reaction (PCR) analysis was used to confirm the results of protein-based electrophoretic methods. Problems inherent in quantitative analysis of cow's milk percentage using protein-based techniques and even more using DNA-based methods were emphasized. Applicability of quantitative real-time PCR for the determination of cow's milk percentage in mixed-milk cheese was shown to be hampered by several factors (e.g., somatic cell count of milk; technological parameters influencing the final DNA concentration in ripened commercial cheese samples). The implementation of certified reference standards (of major relevant cheese groups) containing 50% cow's milk was urgently recommended to enable at least a yes/no decision in commercial mixed-milk cheese samples.
    Keywords: Sheep ; Soy Milk ; Urea ; Dairy Products Industry
    ISSN: 1618-2642
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Analytical and Bioanalytical Chemistry, Oct 1, 2013, Vol.405(25), p.8053(9)
    Description: A rapid ultra-high performance liquid chromatography (UHPLC) protocol for the determination of amino acids as their respective 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatives was successfully applied for assessing free amino acid levels in commercial cheese samples representing typical product groups (ripening protocols) in cheesemaking. Based on the Waters AccQ.Tag[TM] method as a high performance liquid chromatography (HPLC) amino acid solution designed for hydrolyzate analyses, method adaptation onto UHPLC was performed, and detection of AQC derivatives was changed from former fluorescence ([[lambda].sub.Ex] 250 nm/[[lambda].sub.Em] 395 nm) to UV (254 nm). Compared to the original HPLC method, UHPLC proved to be superior by facilitating excellent separations of 18 amino acids within 12 min only, thus demonstrating significantly shortened runtimes (〉35 min for HPLC) while retaining the original separation chemistry and amino acid elution pattern. Free amino acid levels of the analyzed cheese samples showed a high extent of variability depending on the cheese type, with highest total amounts found for original Italian extra-hard cheeses (up to 9,000 mg/100 g) and lowest for surface mold- or bacterial smear-ripened soft cheeses (200-600 mg/100 g). Despite the intrinsic variability in both total and specific concentrations, the established UHPLC method enabled reliable and interferencefree amino acid profiling throughout all cheese types, thus demonstrating a valuable tool to generate high quality data for the characterization of cheese ripening. Keywords HPLC * UHPLC * 6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) * Cheese * Free amino acids
    Keywords: High Performance Liquid Chromatography – Methods ; Amino Acid Synthesis – Methods ; Cheese – Chemical Properties
    ISSN: 1618-2642
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Analytical and Bioanalytical Chemistry, 2013, Vol.405(25), pp.8053-8061
    Description: A rapid ultra-high performance liquid chromatography (UHPLC) protocol for the determination of amino acids as their respective 6-aminoquinolyl- N -hydroxysuccinimidyl carbamate (AQC) derivatives was successfully applied for assessing free amino acid levels in commercial cheese samples representing typical product groups (ripening protocols) in cheesemaking. Based on the Waters AccQ.Tag™ method as a high performance liquid chromatography (HPLC) amino acid solution designed for hydrolyzate analyses, method adaptation onto UHPLC was performed, and detection of AQC derivatives was changed from former fluorescence ( λ Ex 250 nm/ λ Em 395 nm) to UV (254 nm). Compared to the original HPLC method, UHPLC proved to be superior by facilitating excellent separations of 18 amino acids within 12 min only, thus demonstrating significantly shortened runtimes (〉35 min for HPLC) while retaining the original separation chemistry and amino acid elution pattern. Free amino acid levels of the analyzed cheese samples showed a high extent of variability depending on the cheese type, with highest total amounts found for original Italian extra-hard cheeses (up to 9,000 mg/100 g) and lowest for surface mold- or bacterial smear-ripened soft cheeses (200–600 mg/100 g). Despite the intrinsic variability in both total and specific concentrations, the established UHPLC method enabled reliable and interference-free amino acid profiling throughout all cheese types, thus demonstrating a valuable tool to generate high quality data for the characterization of cheese ripening.
    Keywords: HPLC ; UHPLC ; 6-Aminoquinolyl--hydroxysuccinimidyl carbamate (AQC) ; Cheese ; Free amino acids
    ISSN: 1618-2642
    E-ISSN: 1618-2650
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Forest Ecology and Management, 2011, Vol.262(2), pp.105-114
    Description: ► Competition for N between young and adult beech is reduced by seasonal timing. ► Beech seedlings favour N uptake in spring, adult beech trees in autumn. ► Removal of vegetation components does not play a role in this competition. ► Competition between plants and soil microorganisms is, therefore, not avoided. Plant growth, reproduction, and biomass allocation may be affected differently by nitrogen availability depending on tree size and age. In this context, competition for limited N may be avoided by different strategies of N acquisition between different vegetation components (i.e., seedlings, mature trees, other woody and herbaceous understorey). This study investigated in a field experiment whether the competition for N between different vegetation components in beech forests was prevented via seasonal timing of N uptake and affected by microbial N use. For this purpose, a removal approach was used to study the seasonal effects on N uptake and N metabolites in adult beech trees and beech natural regeneration, as well as soil microbial processes of inorganic N production and utilisation. We found that the competition for N between beech natural regeneration and mature beech trees was reduced by seasonal avoidance strategies (“good parenting”) of N uptake regardless of the N sources used. In spring, organic and inorganic N uptake capacity was significantly higher in beech seedlings compared to adult beech trees, whereas in autumn mature beech trees showed the highest N uptake rates. Removal of vegetation components did not result in changes in soil microbial N processes in the course of the growing season. Thus, N resources released by the removal of vegetation components were marginal. This consistency in soil microbial N processes indicates that competition between plants and soil microorganisms for N was not avoided by timing of acquisition during the vegetation period, but existed during the entire growing season. In conclusion, N nutrition in the studied forest ecosystem seems to be optimally attuned to European beech.
    Keywords: Fagus Sylvatica ; N Uptake ; N Metabolites ; Soil Microorganisms ; Soil N Processes ; Removal Approach ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Journal of Chromatography A, 20 March 2015, Vol.1386, pp.98-102
    Description: The level of undenatured acid-soluble β-lactoglobulin can be used as an indicator to assess the heat load applied to liquid milk, thus further allowing the discrimination between milk originating from different thermal production processes. In this work, a new UHPLC method for the rapid determination of bovine β-lactoglobulin in 1.8 min only (total runtime 3 min) is presented using simple UV detection at 205 nm. Separation selectivity for possibly co-eluting other major whey proteins (bovine serum albumin, lactoferrin, α-lactalbumin, immunoglobulin G) was verified, and the method validated for the analysis of liquid milk samples regarding linearity (20–560 μg/mL, 〉 0.99), instrumentation precision (RSDs 〈 2.8%), limits of detection and quantification (7 and 23 mg/L milk), repeatability of sample work-up (RSDs ≤ 2.6%) and method recovery (103%). In total, 71 commercial liquid milk samples produced using different preservation techniques (e.g., thermal or mechanical treatment), hence featuring different applied heat loads, were profiled for their intrinsic undenatured acid-soluble β-lactoglobulin levels. As expected, pasteurized milk showed the highest concentrations clearly above 3000 mg/L due to pasteurization being the mildest thermal treatment, while in contrast, ultra-high temperature heated milk featured the lowest amounts (〈200 mg/L). For extended shelf life (ESL) milk, quite diverse levels were determined ranging from ∼100 up to 4000 mg/L, thus clearly illustrating variable applied heat loads and impacts on the “nativeness” of milk essentially due to the fact that the production technologies used for ESL milk may differ significantly, and are currently not regulated in the EU.
    Keywords: Liquid Milk ; Extended Shelf Life (Esl) Milk ; Whey Proteins ; Β-Lactoglobulin ; Uhplc ; Chemistry
    ISSN: 0021-9673
    E-ISSN: 18733778
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Acta Materialia, 2014, Vol.64, p.241(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.actamat.2013.10.036 Byline: Martin Schloffer, Boryana Rashkova, Thomas Schoberl, Emanuel Schwaighofer, Zaoli Zhang, Helmut Clemens, Svea Mayer Abstract: The intermetallic [beta]-stabilized Ti-43.5Al-4Nb-1Mo-0.1B alloy (in at.%), termed TNM alloy, is designed to be used at elevated temperatures, typically up to 750[degrees]C. To understand the evolution of the microstructures during heat treatments and subsequent creep tests, an understanding of the phase transformations and decomposition reactions that occur is necessary. The present study deals with the development and growth mechanism of the I.sub.o phase, which forms in the [beta].sub.o phase during static annealing treatments and creep tests performed at 750, 780 and 800[degrees]C using an applied stress of 150MPa. In situ high-energy X-ray diffraction experiments were conducted to investigate the decomposition behaviour of the I.sub.o phase during heating as well as to determine its dissolution temperature. High-resolution transmission electron microscopy was used to study the coarsening of I.sub.o grains during creep. The chemical composition of [beta].sub.o and I.sub.o was determined by means of energy dispersive X-ray microanalysis. In particular, the impact of the Mo content on the growth of the I.sub.o grains within the [beta].sub.o matrix was investigated. Additionally, nanohardness measurements in [gamma], [alpha].sub.2, [beta].sub.o and ([beta].sub.o +I.sub.o) grains were performed by cube corner indentation. The results show that [beta].sub.o is the hardest phase in the TiAl-Nb-Mo alloy system when finely dispersed I.sub.o precipitates are present. Article History: Received 29 July 2013; Revised 12 October 2013; Accepted 20 October 2013
    Keywords: Alloys – Mechanical Properties ; Decomposition (Chemistry) – Mechanical Properties ; Intermetallic Compounds – Mechanical Properties ; Hardness (Materials) – Mechanical Properties ; Evolution (Biology) – Mechanical Properties
    ISSN: 1359-6454
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: Food Chemistry, 15 August 2017, Vol.229, pp.452-457
    Description: The aim of this study was to develop a high-throughput UHPLC method for the determination vitamin B active compounds; thiamin, thiamin monophosphate and thiamin diphosphate in bovine milk. In order to sustain the native vitamin B phosphorus esters, sample preparation is crucial. Various acids as well as commonly used enzymes and their enzyme mixtures were compared. Method accuracy was confirmed using certified reference material as well as comparison with the corresponding CEN method, and was found to be satisfactory. Studied milk samples showed significant amounts of thiamin monophosphate, which can make up to 53.9% of the total vitamin B content in commercial milk, and up to 78% in raw milk. Moreover, a tremendous variation of the total content of vitamin B was observed between single cows, which ranged from 0.24 mg/L up to 0.54 mg/L of total vitamin B .
    Keywords: Thiamin ; Thiamin Phosphate Esters ; Uhplc ; Milk ; Chemistry ; Diet & Clinical Nutrition ; Economics
    ISSN: 0308-8146
    E-ISSN: 1873-7072
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Food Chemistry, 30 June 2018, Vol.252, pp.22-27
    Description: Analysis of proteins in bovine milk is usually tackled by time-consuming analytical approaches involving wet-chemical, multi-step sample clean-up procedures. The use of external cavity-quantum cascade laser (EC-QCL) based IR spectroscopy was evaluated as an alternative screening tool for direct and simultaneous quantification of individual proteins (i.e. casein and β-lactoglobulin) and total protein content in commercial bovine milk samples. Mid-IR spectra of protein standard mixtures were used for building partial least squares (PLS) regression models. A sample set comprising different milk types (pasteurized; differently processed extended shelf life, ESL; ultra-high temperature, UHT) was analysed and results were compared to reference methods. Concentration values of the QCL-IR spectroscopy approach obtained within several minutes are in good agreement with reference methods involving multiple sample preparation steps. The potential application as a fast screening method for estimating the heat load applied to liquid milk is demonstrated.
    Keywords: External Cavity-Quantum Cascade Laser (EC-Qcl) ; Total Protein ; Casein ; Β-Lactoglobulin ; Bovine Milk Analysis ; Chemometrics ; Chemistry ; Diet & Clinical Nutrition ; Economics
    ISSN: 0308-8146
    E-ISSN: 1873-7072
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Analytical and Bioanalytical Chemistry, 2012, Vol.403(10), pp.3031-3040
    Description: The substitution of ewe’s and goat’s milk for cheaper cow’s milk is still a fraudulent practice in the dairy industry. Moreover, soy-based products (e.g., soy milk, yoghurt) have to be checked for cow’s milk as they are an alternative for people suffering from an allergy against bovine milk proteins. This work reports the evaluation of different protein-based electrophoretic methods and DNA-based techniques for the qualitative detection as well as the quantitative determination of cow’s milk percentage in dairy and soy milk products. Isoelectric focusing (IEF) of γ-caseins using an optimized pH gradient was appropriate not only for the detection of cow’s milk, but also for an estimation of cow’s milk percentage in mixed-milk cheese varieties. Urea-polyacrylamide gel electrophoresis (PAGE) proved the method of choice to detect cow’s milk in soy milk products, whereas IEF and SDS-PAGE of proteins were not applicable due to false-positive results. Polymerase chain reaction (PCR) analysis was used to confirm the results of protein-based electrophoretic methods. Problems inherent in quantitative analysis of cow’s milk percentage using protein-based techniques and even more using DNA-based methods were emphasized. Applicability of quantitative real-time PCR for the determination of cow’s milk percentage in mixed-milk cheese was shown to be hampered by several factors (e.g., somatic cell count of milk; technological parameters influencing the final DNA concentration in ripened commercial cheese samples). The implementation of certified reference standards (of major relevant cheese groups) containing 50% cow’s milk was urgently recommended to enable at least a yes/no decision in commercial mixed-milk cheese samples. Figure Austrian cheese variety manufactured from cow’s, sheep’s and goat’s milk
    Keywords: Milk species identification ; Cow’s milk percentage ; Mixed-milk cheese ; Electrophoresis ; PCR ; Quantitative real-time PCR
    ISSN: 1618-2642
    E-ISSN: 1618-2650
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Current Analytical Chemistry, 2014, Vol.10(3), p.366-374
    Description: A new UHPLC protocol for the determination of amino acids after pre-column derivatization with 6- aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) was presented. Applying a simple and easy to prepare binary eluent system, the 20 major proteinogenic amino acids were separated in about 7 min with a total runtime of 10.5 min until the next injection. Since AQC amino acid derivatives were primarily designed to be used with fluorescence detection but facilitate UV detection as well, both approaches were evaluated for their applicability with the established UHPLC method. 6-aminoquinoline, the hydrolysis by-product of derivatization which implies similar absorbance as amino acid derivatives, was effectively separated prior to the polar amino acids, hence no interferences in UV detection were observed. For UV detection at 254 nm, all amino acids exhibited a quite similar response, whereas the respective fluorescence yield at 395 nm emission (excitation at 245 nm) indicated significant dependencies from the applied conditions mainly affected by aqueous quenching. Regarding the possible sensitivity compared to UV, fluorescence detection proved to be superior with detection limits ranging down to the low fmol level. Additionally, the established method was successfully applied to analyze amino acid levels intrinsic to commercial hydrolysates/peptones, that were primarily destined for microbiological use. The found proportion of amino nitrogen ranged from 8% for soy protein acid hydrolysate to 2% for fish peptone, while both detection approaches proved to be equally suitable for the given application.
    Keywords: 6-Aminoquinolyl-N-Hydroxysuccinimidyl Carbamate Amino Acids Derivatization Fluorescence Detection Hydrolysate Uhplc Uv Detection.
    ISSN: 1573-4110
    E-ISSN: 1875-6727
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages