Protein nitrogen in fruits, vegetables, and meats by a modified Kjeldahl method: A quantitative analysis experiment

1962 ◽  
Vol 39 (7) ◽  
pp. 365
Author(s):  
Clifton E. Meloan
Keyword(s):  
Quantitative Analysis ◽  
Protein Nitrogen ◽  
Analysis Experiment ◽  
Kjeldahl Method

Effect of Nitrates on Determination of Protein Nitrogen by Kjeldahl Method

1942 ◽  
Vol 25 (3) ◽  
pp. 769-772
Author(s):  
Eugene I Whitehead ◽  
Oscar E Olson
Keyword(s):  
Protein Nitrogen ◽  
Kjeldahl Method

scholarly journals Spectrophotometric Determination of Organic Nitrogen by a Modified Lassaigne Method and Its Application to Meat Products and Baby Food

2002 ◽  
Vol 85 (4) ◽  
pp. 971-977 ◽  
Author(s):  
Birsen Demirata ◽  
Resat Apak ◽  
Hüseyin Afsar ◽  
Izzet Tor
Keyword(s):  
Meat Products ◽  
Molar Absorptivity ◽  
Baby Food ◽  
Protein Nitrogen ◽  
Colorimetric Measurement ◽  
Total Digestion ◽  
Kjeldahl Method ◽  
The Mean ◽  
Aqueous Leachate

Abstract A modified Lassaigne method was developed for N determination based on fusion of the organic substance with metallic Na, conversion of the cyanide in the aqueous leachate to thiocyanate by ammonium polysulfide treatment, and colorimetric measurement of the thiocyanate formed by the addition of excessive ferric ions in acidic medium. The mean molar absorptivity of the Fe(NCS)2+ complex at 480 nm is 2.96 × 103 L/mol·cm, enabling quantitation of 0.25–7.72 ppm N (linear range) in the final solution. The relative amounts of Na, (NH4)2S2, and Fe(III) with respect to nitrogen in the analyte were optimized. The developed method was successfully applied to the determination of N in various brands of baby food, and it was compared statistically with the conventional Kjeldahl and elemental analysis methods. Protein nitrogen in a number of meat products was also precisely determined by the developed method. Thus, the total digestion time of the conventional Kjeldahl method was reduced considerably (e.g., to approximately 15 min for a dried sample) with a relatively simple spectrophotometric method requiring no sophisticated instrumentation.

Separation of an APC mixture. A quantitative analysis experiment

1976 ◽  
Vol 53 (11) ◽  
pp. 731
Author(s):  
Paul Haddad ◽  
Malcolm Rasmussen
Keyword(s):  
Quantitative Analysis ◽  
Analysis Experiment

Protein Nitrogen Unit Precipitation Procedure for Allergenic Extracts: Collaborative Study

1981 ◽  
Vol 64 (6) ◽  
pp. 1435-1438
Author(s):  
Joan C May ◽  
Jenny T C Sih ◽  
◽  
Allergy Laboratories ◽  
J Best ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Coefficient Of Variation ◽  
Collaborative Study ◽  
Precipitation Method ◽  
Protein Nitrogen ◽  
Accuracy And Precision ◽  
Precipitation Procedure ◽  
Allergenic Extracts ◽  
Kjeldahl Method ◽  
Repeatability Standard Deviation

Abstract Protein nitrogen unit (PNU) determination is one of the methods used to test and label the concentration of allergenic extracts. This recently standardized method is applicable to all allergenic extracts. One PNU/mL is equivalent to 1 × 10−5 mg nitrogen determined to be in the material precipitated from 1 m l allergenic extract by phosphotungstic acid (PTA), a protein precipitant. The nitrogen is quantitated by the Kjeldahl method or another analytical method of equivalent accuracy and precision. A collaborative study of the optimized PNU precipitation method in which 6 samples were analyzed in duplicate by 6 laboratories using the Kjeldahl method for the determination of nitrogen yielded a mean of 0.1358 mg N/ml, a repeatability standard deviation and coefficient of variation of 0.0071 mg N/mL and 5.23%, respectively, and a reproducibility standard deviation and coefficient of variation of 0.0188 mg N/mL and 13.84%, respectively. The method has been adopted official first action.

scholarly journals ACEI and antioxidant peptides release during ripening of Mexican Cotija hard cheese

2016 ◽  
Vol 5 (3) ◽  
pp. 85 ◽  
Author(s):  
Leticia Hernández-Galán ◽  
Anaberta Cardador-Martínez ◽  
Daniel Picque ◽  
Henry Eric Spinnler ◽  
Micloth López-del-Castillo Lozano ◽  
...  
Keyword(s):  
Ace Inhibition ◽  
Soluble Nitrogen ◽  
Converting Enzyme ◽  
Antioxidant Peptides ◽  
Protein Nitrogen ◽  
Kjeldahl Method ◽  
Inhibitory Activities ◽  
Highly Correlated ◽  
Ace Inhibitory ◽  
Hard Cheese

<p>Cotija cheese is an artisanal Mexican cheese produced with raw cow´s milk. Our objective was to measure the antioxidant and angiotensin converting enzyme (ACE) inhibitory activities of the peptides released during its ripening. For that, Cotija cheeses were ripened 6 months in a chamber at 25 ºC without humidity control. Weekly samples were taken to determine acid soluble nitrogen (ASN), non-protein nitrogen (NPN) and ethanol soluble nitrogen (EtOH-SN) indexes, by Kjeldahl method. Antioxidant and ACE inhibitory activities were measured by spectrophotometry and HPLC methods, respectively. Peptides in each nitrogen fraction were determined by HPLC. Our results showed that during ripening of Cotija cheeses peptides with antioxidant and ACE inhibitory activities were released and increased through ripening time reaching a maximum of 79.8 % of 2,2- diphenyl-1-picrylhydrazyl (DPPH) discoloration and 100 % of ACE inhibition at the end of ripening. Both activities were highly correlated with the types of peptides present in each fraction.</p>

Modeling with Multiple Correlated Spectral Data Based on Approximating the Nonlinear Spectrum Induced by Scattering

2021 ◽  
pp. 000370282110365
Author(s):  
Yongshun Luo ◽  
Gang Li ◽  
Guosong Shan ◽  
Ling Lin
Keyword(s):  
Quantitative Analysis ◽  
Spectral Data ◽  
Prediction Accuracy ◽  
Data Set ◽  
Analysis Experiment ◽  
Scattering Material ◽  
Modeling Data ◽  
Highly Correlated ◽  
Equal Space ◽  
Strong Scattering

In the spectral quantitative analysis of scattering solution, the improvement of accuracy is seriously restricted by the nonlinearity caused by scattering, and even the measurement will fail due to the influence of scattering. The important reasons are that the modeling variables are greatly affected by nonlinearity, and the information contained in the modeling data cannot represent the scattering characteristics. In this paper, a method is proposed, in which the spectral data of several optical pathlengths with equal space are combined as the modeling data set of a sample. These highly correlated spectral data contain relatively nonlinear information. The addition of the spectral data provides more options for the selection of principal components in modeling with PLS method. By giving lower weight to the corresponding wavelength which is greatly affected by scattering, the model is insensitive to scattering and the prediction accuracy is improved. Through the spectral quantitative analysis experiment on strong scattering material, the prediction accuracy of the model was 61.7% higher than that of the traditional method and was 58.5% higher than that of the variable sorting for normalization method. The feasibility of the method is verified.

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