Uncertainty of nitrogen determination by the Kjeldahl method

Anglov, Thomas; Petersen, I. M.; Kristiansen, J.

doi:10.1007/s007690050423

Cited by 20 publications

(2 citation statements)

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“…In the analytical process, the highest contribution towards the uncertainty comes from the extraction procedure. This is due to repeatability of extraction and to the large amount of volumetric glassware used [37]. For the vegetables under study, homogeneity is the greatest contributor to uncertainty amongst the steps of the feasibility study, which is probably related to the variability of the nitrate content.…”

Section: Homogeneitymentioning

confidence: 97%

The need for reference materials when monitoring nitrate intake

Castanheira

Oliveira

Valente

et al. 2004

Analytical and Bioanalytical Chemistry

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Whether dietary exposure to nitrate metabolites is detrimental or beneficial to human health has long been a matter of controversy. In spite of no consistent epidemiological evidence, nitrate metabolites are associated with the formation of carcinogenic-nitrosamines and gastric cancer. Furthermore, recent studies demonstrate that ingested nitrate plays a role in host defence against gastrointestinal pathogenic bacteria. Analytical values of nitrate content in foods are essential for estimating nitrate intake. The analytical process is of paramount importance for assessing human nitrate exposure and for establishing a link between these exposures and the current and future observed health effects. Therefore, the quality assurance of the measurement process is crucial to obtaining reliability, comparability and traceability of results. Certified Reference Materials (CRM) should play a role in the consistency of the measurement process. However, the availability of nitrate CRMs is still poor. When food monitoring is demanded, an approach could be to use In House Reference Materials (IHRM), prepared at a high metrological level, and all preparation steps should be quality driven. IHRMs were prepared, and available CRMs were used to provide traceability of the process. The homogeneity of IHRM was evaluated using an appropriate statistical design. The stability was monitored using an isochronous method. The material shelf life and storage conditions are presented. HPLC was optimised for the determination of nitrates in four vegetable categories. When a suite of IHRMs were used, the response of the HPLC system was linear over the range 1 to 8 mg L(-1). The detection limit for these compounds was 0.2 microg L(-1) and the determination limit 1.2 microg L(-1). The relationship between measurement uncertainty and critical points of the analytical process is presented. The differences in observed relative uncertainty between food categories could reflect current limitations in the food matrix reference materials.

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Section: Homogeneitymentioning

confidence: 97%

The need for reference materials when monitoring nitrate intake

Castanheira

Oliveira

Valente

et al. 2004

Analytical and Bioanalytical Chemistry

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“…At 500 o C, carbonized samples were burned until pale, and the pale ash amount was placed in a drying vessel for cooling until it reached room temperature, and then ash was weighted. Total protein was determined by Kjeldahl method, [17] and total fat was determined by Soxhlet extraction method. [18] pH and color Fish fillets (10 g) were grounded and homogenized into a paste with mincing machine at 5,000 rpm for 2 min, and the pH of paste was quantified thrice by a pH meter (PHS-3C-3, Leici Company, Shanghai, China).…”

Section: Proximate Composition Analysesmentioning

confidence: 99%

Chlorogenic acid osmosis of snakehead fish: a novel approach to maintain quality and suppress deterioration during storage

Cao

Islam

Duan

et al. 2020

International Journal of Food Properties

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To prevent the degradation, snakehead fish fillets were infiltrated in 4% chlorogenic acid solution for 10, 20, and 30 min; which correspond to chlorogenic acid concentration of 0.2%, 0.5%, 0.7% in the infiltrated samples, respectively. Treated fish fillets were then stored at 2 ± 0.5°C for 2 weeks and were evaluated for total volatile base nitrogen (TVB-N), trimethylamine (TMA), pH, acid value (AV), peroxide value (POV), total bacterial count, and sensory qualities. Results advocated that chlorogenic acid penetration inactivated about 2-log CFU/g microorganism, while TVB-N and TMA were limited to about 10 mg/100 g. Rising kinetics of pH, AV, and POV were impeded markedly as well as 2 weeks of acceptable storage was achieved. Chlorogenic acid penetration features promotion of fish quality, decrease of microbial load and textures. This novel treatment can be applied industrially in tenderization of meat, storage of meat, and microbial inhibition of meat during preservation.

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Enhancing l-malate production of Aspergillus oryzae FMME218-37 by improving inorganic nitrogen utilization

Ding

Luo

Zhou

et al. 2018

Appl Microbiol Biotechnol

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Microbial L-malate production from renewable feedstock is a promising alternative to petroleum-based chemical synthesis. However, high L-malate production of Aspergillus oryzae was achieved to date using organic nitrogen, with inorganic nitrogen still unable to meet industrial applications. In the current study, we constructed a screening system and nitrogen supply strategy to improve L-malate production with ammonium sulphate [(NH)SO] as the sole nitrogen source. First, we generated and identified a high-producing mutant FMME218-37, which stably boosted L-malate production from 30.73 to 78.12 g/L, using a combined screening system with morphological characteristics. Then, by analyzing the fermentation parameters and physiological characteristics, we further speculated the key factor was the unbalance of carbon and nitrogen absorption. Finally, the titer and productivity of L-malate was increased to 95.2 g/L and 0.57 g/(L h) by regulating the nitrogen supply module to balance carbon and nitrogen absorption, which represented the highest level in A. oryzae with (NH)SO as nitrogen source achieved to date. Moreover, our findings using a low-cost substrate may lead to building an economical cell factory of A. oryzae for L-malate production.

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Uncertainty of nitrogen determination by the Kjeldahl method

Cited by 20 publications

References 0 publications

The need for reference materials when monitoring nitrate intake

The need for reference materials when monitoring nitrate intake

Chlorogenic acid osmosis of snakehead fish: a novel approach to maintain quality and suppress deterioration during storage

Enhancing l-malate production of Aspergillus oryzae FMME218-37 by improving inorganic nitrogen utilization

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