Indirect and direct determination of the casein content of milk by Kjeldahl nitrogen analysis: collaborative study
The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For...
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| Veröffentlicht in: | Journal of AOAC International 1998-07, Vol.81 (4), p.763-774 |
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| creator | Lynch, J.M. (Cornell University, Ithaca, NY.) Barbano, D.M Fleming, J.R |
| description | The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42-3.05% by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen X 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDR) = 1.287%, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt%), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560%, RSDR = 0.841; direct casein method (wt%), mean = 2.575, sr = 0.015, SR = 0.025, RSDr = 0.597%, RSDR = 0.988%. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21, 991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC International |
| doi_str_mv | 10.1093/jaoac/81.4.763 |
| format | Article |
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(Cornell University, Ithaca, NY.) ; Barbano, D.M ; Fleming, J.R</creator><creatorcontrib>Lynch, J.M. (Cornell University, Ithaca, NY.) ; Barbano, D.M ; Fleming, J.R</creatorcontrib><description>The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42-3.05% by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen X 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDR) = 1.287%, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt%), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560%, RSDR = 0.841; direct casein method (wt%), mean = 2.575, sr = 0.015, SR = 0.025, RSDr = 0.597%, RSDR = 0.988%. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21, 991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC International</description><identifier>ISSN: 1060-3271</identifier><identifier>EISSN: 1944-7922</identifier><identifier>DOI: 10.1093/jaoac/81.4.763</identifier><identifier>PMID: 9680702</identifier><language>eng</language><publisher>Gaithersburg, MD: AOAC International</publisher><subject>ALIMENTOS ; ANALISIS CUANTITATIVO ; ANALYSE QUANTITATIVE ; ANALYTICAL METHODS ; Animals ; AZOTE ; Biological and medical sciences ; CASEIN ; CASEINA ; CASEINE ; Caseins - analysis ; Caseins - chemistry ; COMPOSICION APROXIMADA ; COMPOSITION GLOBALE ; CONTROLE DE PERFORMANCE ; ENSAYO ; EVALUACION ; EVALUATION ; FOOD ANALYSIS ; FOOD COMPOSITION ; Food industries ; FOODS ; Fundamental and applied biological sciences. Psychology ; IMPROVEMENT ; Indicators and Reagents ; KJELDAHL METHOD ; LAIT ; LECHE ; MEASUREMENT ; MEDICION ; MESURE ; MILK ; Milk - chemistry ; Milk and cheese industries. Ice creams ; Milk Proteins - analysis ; MODIFICATION ; NITROGEN ; Nitrogen - analysis ; NITROGENO ; PERFORMANCE TESTING ; PRODUIT ALIMENTAIRE ; PROXIMATE COMPOSITION ; PRUEBAS DE RENDIMIENTO ; QUANTITATIVE ANALYSIS ; Reproducibility of Results ; TECHNIQUE ANALYTIQUE ; TECNICAS ANALITICAS ; TEST PROCEDURE ; TESTAGE ; TESTING</subject><ispartof>Journal of AOAC International, 1998-07, Vol.81 (4), p.763-774</ispartof><rights>1998 INIST-CNRS</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c381t-507b36a22215cedd95017123ccec4a615692051909d2f6cc4fd4bacc7572678c3</citedby></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,776,780,27903,27904</link.rule.ids><backlink>$$Uhttp://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=2315753$$DView record in Pascal Francis$$Hfree_for_read</backlink><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/9680702$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>Lynch, J.M. (Cornell University, Ithaca, NY.)</creatorcontrib><creatorcontrib>Barbano, D.M</creatorcontrib><creatorcontrib>Fleming, J.R</creatorcontrib><title>Indirect and direct determination of the casein content of milk by Kjeldahl nitrogen analysis: collaborative study</title><title>Journal of AOAC International</title><addtitle>J AOAC Int</addtitle><description>The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42-3.05% by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen X 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDR) = 1.287%, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt%), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560%, RSDR = 0.841; direct casein method (wt%), mean = 2.575, sr = 0.015, SR = 0.025, RSDr = 0.597%, RSDR = 0.988%. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21, 991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC International</description><subject>ALIMENTOS</subject><subject>ANALISIS CUANTITATIVO</subject><subject>ANALYSE QUANTITATIVE</subject><subject>ANALYTICAL METHODS</subject><subject>Animals</subject><subject>AZOTE</subject><subject>Biological and medical sciences</subject><subject>CASEIN</subject><subject>CASEINA</subject><subject>CASEINE</subject><subject>Caseins - analysis</subject><subject>Caseins - chemistry</subject><subject>COMPOSICION APROXIMADA</subject><subject>COMPOSITION GLOBALE</subject><subject>CONTROLE DE PERFORMANCE</subject><subject>ENSAYO</subject><subject>EVALUACION</subject><subject>EVALUATION</subject><subject>FOOD ANALYSIS</subject><subject>FOOD COMPOSITION</subject><subject>Food industries</subject><subject>FOODS</subject><subject>Fundamental and applied biological sciences. Psychology</subject><subject>IMPROVEMENT</subject><subject>Indicators and Reagents</subject><subject>KJELDAHL METHOD</subject><subject>LAIT</subject><subject>LECHE</subject><subject>MEASUREMENT</subject><subject>MEDICION</subject><subject>MESURE</subject><subject>MILK</subject><subject>Milk - chemistry</subject><subject>Milk and cheese industries. Ice creams</subject><subject>Milk Proteins - analysis</subject><subject>MODIFICATION</subject><subject>NITROGEN</subject><subject>Nitrogen - analysis</subject><subject>NITROGENO</subject><subject>PERFORMANCE TESTING</subject><subject>PRODUIT ALIMENTAIRE</subject><subject>PROXIMATE COMPOSITION</subject><subject>PRUEBAS DE RENDIMIENTO</subject><subject>QUANTITATIVE ANALYSIS</subject><subject>Reproducibility of Results</subject><subject>TECHNIQUE ANALYTIQUE</subject><subject>TECNICAS ANALITICAS</subject><subject>TEST PROCEDURE</subject><subject>TESTAGE</subject><subject>TESTING</subject><issn>1060-3271</issn><issn>1944-7922</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>1998</creationdate><recordtype>article</recordtype><sourceid>EIF</sourceid><recordid>eNpNkMFPHSEQh0ljY63ttTcTDqa3fQK7C4s382JbU5MeWs9kdmCV5y5Y4DV5_32xbkxPTJhvvpn8CPnE2YYz3V7sIAJeDHzTbZRs35ATrruuUVqIo1ozyZpWKP6OvM95x1jHJRPH5FjLgSkmTki6CdYnh4VCsHQtrSsuLT5A8THQONHy4ChCdj5QjKG4UJ5_Fz8_0vFAv-_cbOFhpsGXFO9dqC6YD9nny4rPM4wxVdUfR3PZ28MH8naCObuP63tK7r5c_9p-a25_fL3ZXt022A68ND1TYytBCMF7dNbqnnHFRYvosAPJe6kF67lm2opJInaT7UZAVL0SUg3YnpLPL96nFH_vXS5m8RldvSe4uM9mYEzolvcV3LyAmGLOyU3mKfkF0sFwZp5DNv9CNgM3nakh14Gz1bwfF2df8TXV2j9f-5AR5ilBQJ9fMVGXqv4_zQTRwH2qyN1PrrWuh_Gq-QuSc49n</recordid><startdate>19980701</startdate><enddate>19980701</enddate><creator>Lynch, J.M. (Cornell University, Ithaca, NY.)</creator><creator>Barbano, D.M</creator><creator>Fleming, J.R</creator><general>AOAC International</general><scope>FBQ</scope><scope>IQODW</scope><scope>CGR</scope><scope>CUY</scope><scope>CVF</scope><scope>ECM</scope><scope>EIF</scope><scope>NPM</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7X8</scope></search><sort><creationdate>19980701</creationdate><title>Indirect and direct determination of the casein content of milk by Kjeldahl nitrogen analysis: collaborative study</title><author>Lynch, J.M. (Cornell University, Ithaca, NY.) ; Barbano, D.M ; Fleming, J.R</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c381t-507b36a22215cedd95017123ccec4a615692051909d2f6cc4fd4bacc7572678c3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1998</creationdate><topic>ALIMENTOS</topic><topic>ANALISIS CUANTITATIVO</topic><topic>ANALYSE QUANTITATIVE</topic><topic>ANALYTICAL METHODS</topic><topic>Animals</topic><topic>AZOTE</topic><topic>Biological and medical sciences</topic><topic>CASEIN</topic><topic>CASEINA</topic><topic>CASEINE</topic><topic>Caseins - analysis</topic><topic>Caseins - chemistry</topic><topic>COMPOSICION APROXIMADA</topic><topic>COMPOSITION GLOBALE</topic><topic>CONTROLE DE PERFORMANCE</topic><topic>ENSAYO</topic><topic>EVALUACION</topic><topic>EVALUATION</topic><topic>FOOD ANALYSIS</topic><topic>FOOD COMPOSITION</topic><topic>Food industries</topic><topic>FOODS</topic><topic>Fundamental and applied biological sciences. Psychology</topic><topic>IMPROVEMENT</topic><topic>Indicators and Reagents</topic><topic>KJELDAHL METHOD</topic><topic>LAIT</topic><topic>LECHE</topic><topic>MEASUREMENT</topic><topic>MEDICION</topic><topic>MESURE</topic><topic>MILK</topic><topic>Milk - chemistry</topic><topic>Milk and cheese industries. Ice creams</topic><topic>Milk Proteins - analysis</topic><topic>MODIFICATION</topic><topic>NITROGEN</topic><topic>Nitrogen - analysis</topic><topic>NITROGENO</topic><topic>PERFORMANCE TESTING</topic><topic>PRODUIT ALIMENTAIRE</topic><topic>PROXIMATE COMPOSITION</topic><topic>PRUEBAS DE RENDIMIENTO</topic><topic>QUANTITATIVE ANALYSIS</topic><topic>Reproducibility of Results</topic><topic>TECHNIQUE ANALYTIQUE</topic><topic>TECNICAS ANALITICAS</topic><topic>TEST PROCEDURE</topic><topic>TESTAGE</topic><topic>TESTING</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Lynch, J.M. (Cornell University, Ithaca, NY.)</creatorcontrib><creatorcontrib>Barbano, D.M</creatorcontrib><creatorcontrib>Fleming, J.R</creatorcontrib><collection>AGRIS</collection><collection>Pascal-Francis</collection><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>CrossRef</collection><collection>MEDLINE - Academic</collection><jtitle>Journal of AOAC International</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Lynch, J.M. (Cornell University, Ithaca, NY.)</au><au>Barbano, D.M</au><au>Fleming, J.R</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Indirect and direct determination of the casein content of milk by Kjeldahl nitrogen analysis: collaborative study</atitle><jtitle>Journal of AOAC International</jtitle><addtitle>J AOAC Int</addtitle><date>1998-07-01</date><risdate>1998</risdate><volume>81</volume><issue>4</issue><spage>763</spage><epage>774</epage><pages>763-774</pages><issn>1060-3271</issn><eissn>1944-7922</eissn><abstract>The classic method for determination of milk casein is based on precipitation of casein at pH 4.6. Precipitated milk casein is removed by filtration and the nitrogen content of either the precipitate (direct casein method) or filtrate (noncasein nitrogen; NCN) is determined by Kjeldahl analysis. For the indirect casein method, milk total nitrogen (TN; Method 991.20) is also determined and casein is calculated as TN minus NCN. Ten laboratories tested 9 pairs of blind duplicate raw milk materials with a casein range of 2.42-3.05% by both the direct and indirect casein methods. Statistical performance expressed in protein equivalents (nitrogen X 6.38) with invalid and outlier data removed was as follows: NCN method (wt%), mean = 0.762, sr = 0.010, SR = 0.016, repeatability relative standard deviation (RSDR) = 1.287%, reproducibility relative standard deviation (RSDR) = 2.146%; indirect casein method (wt%), mean = 2.585, repeatability = 0.015, reproducibility = 0.022, RSDr = 0.560%, RSDR = 0.841; direct casein method (wt%), mean = 2.575, sr = 0.015, SR = 0.025, RSDr = 0.597%, RSDR = 0.988%. Method performance was acceptable and comparable to similar Kjeldahl methods for determining nitrogen content of milk (Methods 991.20, 991.21, 991.22, 991.23). The direct casein, indirect casein, and noncasein nitrogen methods have been adopted by AOAC International</abstract><cop>Gaithersburg, MD</cop><pub>AOAC International</pub><pmid>9680702</pmid><doi>10.1093/jaoac/81.4.763</doi><tpages>12</tpages><oa>free_for_read</oa></addata></record> |
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| source | Oxford University Press Journals All Titles (1996-Current); MEDLINE |
| subjects | ALIMENTOS ANALISIS CUANTITATIVO ANALYSE QUANTITATIVE ANALYTICAL METHODS Animals AZOTE Biological and medical sciences CASEIN CASEINA CASEINE Caseins - analysis Caseins - chemistry COMPOSICION APROXIMADA COMPOSITION GLOBALE CONTROLE DE PERFORMANCE ENSAYO EVALUACION EVALUATION FOOD ANALYSIS FOOD COMPOSITION Food industries FOODS Fundamental and applied biological sciences. Psychology IMPROVEMENT Indicators and Reagents KJELDAHL METHOD LAIT LECHE MEASUREMENT MEDICION MESURE MILK Milk - chemistry Milk and cheese industries. Ice creams Milk Proteins - analysis MODIFICATION NITROGEN Nitrogen - analysis NITROGENO PERFORMANCE TESTING PRODUIT ALIMENTAIRE PROXIMATE COMPOSITION PRUEBAS DE RENDIMIENTO QUANTITATIVE ANALYSIS Reproducibility of Results TECHNIQUE ANALYTIQUE TECNICAS ANALITICAS TEST PROCEDURE TESTAGE TESTING |
| title | Indirect and direct determination of the casein content of milk by Kjeldahl nitrogen analysis: collaborative study |
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