Measurement of casein in milk by Kjeldahl and sodium dodecyl sulfate–polyacrylamide gel electrophoresis

Abstract

Our objectives were to determine if milk casein as a percentage of true protein (CN%TP) estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is equivalent to CN%TP estimated by Kjeldahl, and to determine the proportion of casein (CN), casein proteolysis products (CNPP), and serum protein (SP) from milk true protein (TP) that goes into the Kjeldahl noncasein nitrogen (NCN) filtrate and the proportion that stays in the NCN precipitate using SDS-PAGE. Raw milk samples were collected from 16 mid-lactation Holstein cows twice a week for 2 wk.

Adsorption Properties of Anionic Dyes on Quaternized Microcrystalline Cellulose

“…The nitrogen content of QMCC was measured by the Kjeldahl method using a nitrogen analyzer (KDN-08C(04C), Shanghai Huarui Instrument Co., Ltd.) and calculated by the following equation (eq ): W = 2 T ( V t − V 0 ) × 14.04 m × 100 % where W is the nitrogen content, %; T is the molar concentration of standard sulfuric acid used for titration, mol/L; V 0 is the volume of sulfuric acid standard solution used for blank determination, L; V t is the volume of sulfuric acid standard solution used for sample determination, L; and m is the sample weight, g.…”

Antioxidant and anti-inflammatory protective effects of yellowtail (Seriola quinqueradiata) milt hydrolysates on human intestinal epithelial cells in vitro and dextran sodium sulphate-induced mouse colitis in vivo

“…The Kjeldahl nitrogen determination by an apparatus (Kjeltec 8400, FOSS, Sweden) was used to analyze the crude protein content of YMH. 13 The amino acid composition of the YMH samples was determined using an amino acid analyzer (L-8500A, Hitachi Co., Tokyo, Japan) according to Jiang et al (2019) 14 after being hydrolyzed in 6 M HCl for 24 h at 110 °C under vacuum in the presence of 1% phenol (v/v). The calcium, zinc, iron and selenium content of YMH was analyzed on a Agilent 8800 Triple Quadrupole ICP-MS system (Agilent Technologies Inc., CA, USA).…”

“…The Kjeldahl nitrogen determination by an apparatus (Kjeltec 8400, FOSS, Sweden) was used to analyze the crude protein content of YMH. 13 The amino acid composition of the YMH samples was determined using an amino acid analyzer (L-8500A, Hitachi Co., Tokyo, Japan) according to Jiang et al…”

Chemical Composition and Phytochemical Screening of Juniperus Phoenicea L.: Evaluation of Antioxidant Activity, Minerals, and Bioactive Compounds

“…In this method, the plant material is oxidized with concentrated sulfuric acid, which oxidizes all the components except for the nitrogen present in proteins. The nitrogen is subsequently reduced to ammonia, which is determined through back titration in the presence of a methyl red indicator (28). The total protein content of plants can be calculated by converting the percentage of nitrogen using the equation below:…”