Abstract:Summary -After a short description of bovine milk proteins, the various methods of current or potential use for detecting and determining them in dairy products are reviewed. This includes, first, the determination of total protein from nitrogen analysis, dye-binding capacity, infra-red spectrometry and amino acid analysis. The methods that allow determination of sorne milk protein fractions of interest (whole casein, whey proteins,~-Iactoglobulin) are then given. They include the Aschaffenburg-Rowland procedu… Show more
“…They point out the difficulty in obtaining accurate or “true” NPCF and acknowledge that researchers rely on amino acid composition to derive these factors but argue that these methods do not account for the molecular weight of the prosthetic groups (glycosylated, phosphorylated). Marriotti et al () and Ribadeau‐Dumas and Grappin, acknowledge that including the weight of prosthetic groups raises the NPCF value but they question whether it overrepresents the delivery of amino acids per se. It should be noted that the inclusion of prosthetic group weights in the NPCF calculation is only conducted by dairy protein analysts.…”
Section: Npcf For Soybean Proteinmentioning
confidence: 99%
“…In the case of soybeans, the overall number of proteins contributing to total protein (Schmutz et al, ) is significantly higher than that of milk protein (Farrell Jr. et al, ); therefore, it is unlikely that using primary sequences for NPCF calculations would be practical. Also, Ribadeau‐Dumas and Grappin, noted “that experimental determination of the Kjeldahl factor on (pure) protein fractions leads to substantial discrepancies from the theoretical values obtained from amino acid sequences.”…”
Protein content in foods and feeds is measured indirectly by nitrogen determination, requiring a nitrogen‐to‐protein conversion factor (NPCF). Historically, 6.25 was applied to all proteins based on two assumptions: (1) all proteins had a nitrogen content of 16% (100/16 = 6.25) and (2) all nitrogen was derived from protein. Amino acid analyses revealed that a conversion factor of 6.25 overestimated the protein content of most foods due to variations in amino acid profiles and nonprotein nitrogen. The lack of standardization of methods to determine food‐specific NPCF has resulted in continued use of 6.25 and inconsistent development of new factors. This review summarizes efforts made to derive NPCF for various foods. Soy protein has been the subject of considerable debate since publication of the “Jones factors” in 1931, which based the soy conversion factor of 5.71 on the nitrogen content of glycinin. Nonetheless, 6.25 is still used by the soy industry, analytic associations, and government regulatory bodies. Given the impact to the valuation of soy protein products and food relabeling costs, changes to soy alone appear discriminatory in the absence of standardized methods for developing NPCF for all proteins. Proposed solutions include (1) developing a consensus method to determine NPCF applicable to all foods, (2) applying standardized NPCF to measure protein in all foods and assessing the economic, nutritional, and regulatory consequences equitably, and (3) developing standardized direct methods to measure protein, such as amino acid analyses, in foods intended as single sources in vulnerable populations where more accurate measurement and reducing any risk of adulteration with nonprotein nitrogen are essential.
“…They point out the difficulty in obtaining accurate or “true” NPCF and acknowledge that researchers rely on amino acid composition to derive these factors but argue that these methods do not account for the molecular weight of the prosthetic groups (glycosylated, phosphorylated). Marriotti et al () and Ribadeau‐Dumas and Grappin, acknowledge that including the weight of prosthetic groups raises the NPCF value but they question whether it overrepresents the delivery of amino acids per se. It should be noted that the inclusion of prosthetic group weights in the NPCF calculation is only conducted by dairy protein analysts.…”
Section: Npcf For Soybean Proteinmentioning
confidence: 99%
“…In the case of soybeans, the overall number of proteins contributing to total protein (Schmutz et al, ) is significantly higher than that of milk protein (Farrell Jr. et al, ); therefore, it is unlikely that using primary sequences for NPCF calculations would be practical. Also, Ribadeau‐Dumas and Grappin, noted “that experimental determination of the Kjeldahl factor on (pure) protein fractions leads to substantial discrepancies from the theoretical values obtained from amino acid sequences.”…”
Protein content in foods and feeds is measured indirectly by nitrogen determination, requiring a nitrogen‐to‐protein conversion factor (NPCF). Historically, 6.25 was applied to all proteins based on two assumptions: (1) all proteins had a nitrogen content of 16% (100/16 = 6.25) and (2) all nitrogen was derived from protein. Amino acid analyses revealed that a conversion factor of 6.25 overestimated the protein content of most foods due to variations in amino acid profiles and nonprotein nitrogen. The lack of standardization of methods to determine food‐specific NPCF has resulted in continued use of 6.25 and inconsistent development of new factors. This review summarizes efforts made to derive NPCF for various foods. Soy protein has been the subject of considerable debate since publication of the “Jones factors” in 1931, which based the soy conversion factor of 5.71 on the nitrogen content of glycinin. Nonetheless, 6.25 is still used by the soy industry, analytic associations, and government regulatory bodies. Given the impact to the valuation of soy protein products and food relabeling costs, changes to soy alone appear discriminatory in the absence of standardized methods for developing NPCF for all proteins. Proposed solutions include (1) developing a consensus method to determine NPCF applicable to all foods, (2) applying standardized NPCF to measure protein in all foods and assessing the economic, nutritional, and regulatory consequences equitably, and (3) developing standardized direct methods to measure protein, such as amino acid analyses, in foods intended as single sources in vulnerable populations where more accurate measurement and reducing any risk of adulteration with nonprotein nitrogen are essential.
“…Total protein (TP), soluble protein (SP) and tCN contents were calculated according to the method of Ribadeau-Dumas and Grappin [29]. The pH 4.6 insoluble peptides or IP (including g-CN) part of tCN was determined with fast protein liquid chromatography (FPLC) with a Mono Q HR 5/5 anion exchange column (Pharmacia, Uppsala, Sweden) according to the method adapted by Le Roux et al [16].…”
-Lipopolysaccharide experimental mastitis was performed in order to obtain the same milk composition change involved in a clinical mastitis without, however, any bacterial proteolytic participation. Whey from milk with a high somatic cell count (SCC) had a lower mitogenic effect on anti-human prolactin-hybridoma (anti-hPL) cell culture but a greater immunostimulating effect than that of the fetal calf serum regularly used in cell culture. This immunostimulating effect was more pronounced when expressed per cell, with an effect two-to three-fold higher than that of fetal calf serum (P < 0.01), which illustrated the efficiency of such a complement.
Cell culture / whey / proteolysis / mastitisRésumé -Prolifération et production d'immunoglobulines d'hybridomes cultivés sur lactosérum de mammite. Une mammite expérimentale à lipopolysaccharide a été menée en vue d'obtenir le même changement de composition du lait que celui observé dans les cas de mammite clinique, en éliminant toutefois toute interaction avec la protéolyse bactérienne. Le lactosérum issu d'un lait à fort dénombrement cellulaire (DC) avait un effet mitogénique plus faible sur une culture cellulaire d'hybridomes anti-prolactine humaine (anti-hPL) mais toutefois un effet immunostimulant plus important que le sérum foetal de veau. Cet effet immunostimulant a été plus marqué lorsqu'il était exprimé par cellule, avec un effet 2 à 3 fois supérieur à celui observé avec le sérum de veau foetal (P < 0,01), traduisant l'efficacité de la complémentation par un lactosérum issu d'un lait à fort DC.Culture cellulaire / lactosérum / protéolyse / mammite
“…X Present address: Centro de Ciencias Experimentales y Tecnicas, Universidad San Pablo-CEU, 28668-Madrid, Spain. of the neonatal carcass is fat, compared with about 160 g/kg in humans (Pettigrew, 1981;Gurr, 1988)) but receives milk with a high fat content compared with many other terrestrial mammals (70 to 90 g/kg compared with about 40 g/kg in human milk) (Ribadeau-Dumas, 1983;Gurr, 1988). X Present address: Centro de Ciencias Experimentales y Tecnicas, Universidad San Pablo-CEU, 28668-Madrid, Spain. of the neonatal carcass is fat, compared with about 160 g/kg in humans (Pettigrew, 1981;Gurr, 1988)) but receives milk with a high fat content compared with many other terrestrial mammals (70 to 90 g/kg compared with about 40 g/kg in human milk) (Ribadeau-Dumas, 1983;Gurr, 1988).…”
Plasma very low density lipoproteins (VLDL) of gilts were separated into two sub fractions according to their affinity for heparin. The proportion of VLDL present as subfraction 2 (higher affinity for heparin) varied, according to the genetic line of the pigs, between 0-21 and 0-78 in virgin gilts. The proportions were related to the variation in piglet survival in the same nine genetic lines by a quadratic equation, which predicted that greater than 90% survival to weaning was to be found in piglets born to gilts having between about 0-3 and 0-7 of their VLDL as subfraction 2. This observation suggests a simple measurement that could be used in the selection of sows for a breeding programme. The proportion of subfraction 2 fell throughout pregnancy in each of three genetic lines measured and only returned to pre-pregnant values after weaning: these changes did not correlate with the changes in the lipid composition of plasma VLDL measured during pregnancy and lactation. The findings suggest a role for the VLDL subfractions in controlling the nutrition of the neonatal pig.
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