The casein micelle: Historical aspects, current concepts and significance

Fox, P. F.; Brodkorb, André

doi:10.1016/j.idairyj.2008.03.002

Cited by 313 publications

(200 citation statements)

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“…Fox & Brodkorb (2008) destacam a ação estabilizante da kappa-caseína, ao realizar a interface entre o interior da micela, onde se concentram as caseínas mais hidrofóbicas, e o ambiente aquoso, o que atua como uma barreira física e eletrostática à agregação. Entretanto, o resultado deste trabalho discorda dos descritos por Botaro et al (2007) e Lopes (2008), que não verificaram diferenças no percentual de κ-caseína entre leite estável e instável.…”

Section: Resultsunclassified

Caracterização eletroforética de proteínas e estabilidade do leite em vacas submetidas à restrição alimentar

Barbosa

Fischer

Ribeiro³

et al. 2012

Pesq. agropec. bras.

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Resumo -O objetivo deste trabalho foi avaliar os efeitos da restrição alimentar sobre a produção de leite bovino e sobre seu perfil eletroforético de proteínas, bem como relacioná-los à estabilidade do leite pelo teste do álcool. Foram conduzidos dois experimentos com vacas Jersey: no primeiro, avaliou-se o efeito da redução de 40% na alimentação fornecida a vacas semiconfinadas; no segundo, avaliou-se o efeito da restrição de 30% do conteúdo de nutrientes digestíveis totais na alimentação de vacas confinadas. As frações proteicas foram determinadas por eletroforese, e sua quantificação por meio de análises de imagens. As amostras de leite foram classificadas conforme estabilidade no teste do álcool a 72°GL. A restrição alimentar de 40% a vacas semiconfinadas reduziu a produção de leite, mas não alterou a composição de proteínas lácteas e a estabilidade do leite; neste caso, o leite instável apresentou maiores teores de β-caseína e de proteínas totais, porém menor proporção de κ-caseína em comparação ao leite estável. A restrição de 30% do aporte energético a vacas confinadas não reduziu a produção leiteira, porém diminuiu a percentagem de albumina sérica bovina e a estabilidade no teste do álcool; neste caso, o leite instável e o estável não diferiram quanto às proteínas lácteas.Termos para indexação: b-caseína, κ-caseína, confinamento, eletroforese, leite instável não ácido, teste do álcool. Electrophoretic characterization of proteins and milk stability of cows submitted to feeding restrictionAbstract -The objective of this work was to evaluate the feeding restriction effects on milk yield and on its electrophoretic protein profile, and to relate them to milk stability to the alcohol test. Two experiments were carried out with Jersey cows: in the first one, the effect of 40% feed restriction was evaluated on semiconfined cows; in the second one, the effect of 30% reduction in total digestive nutrients was evaluated on confined cows. Protein fractions were determined by electrophoresis and their quantification was done by image analysis. Milk samples were classified according to their stability in the 72°GL-alcohol test. The 40% feed restriction for semiconfined cows decreased milk yield, but it did not change milk protein contents and stability; in this case, unstable milk showed larger contents of β-casein and total proteins, but lower κ-casein in comparison to stable milk. The 30% restriction of energy supply for confined cows did not reduce milk yield, but decreased the percentage of serum bovine albumin and milk stability; in this case, unstable and stable milk did not differ as for protein fractions.

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Section: Resultsunclassified

Caracterização eletroforética de proteínas e estabilidade do leite em vacas submetidas à restrição alimentar

Barbosa

Fischer

Ribeiro³

et al. 2012

Pesq. agropec. bras.

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“…It was acquired originally from a supposed similarity between the self-association behavior of casein, particularly β-and κ-CN, and the formation of surfactant micelles (Fox and Brodkorb, 2008). It was reinforced by the use of the Bigelow hydrophobicity scale (Bigelow, 1967), which classified β-and κ-CN as being among the most hydrophobic proteins known to science.…”

Section: Quaternary Structures and The Hydrophobic Effectmentioning

confidence: 99%

Invited review: Caseins and the casein micelle: Their biological functions, structures, and behavior in foods

Holt

Carver

Ecroyd

et al. 2013

Journal of Dairy Science

381

240

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A typical casein micelle contains thousands of casein molecules, most of which form thermodynamically stable complexes with nanoclusters of amorphous calcium phosphate. Like many other unfolded proteins, caseins have an actual or potential tendency to assemble into toxic amyloid fibrils, particularly at the high concentrations found in milk. Fibrils do not form in milk because an alternative aggregation pathway is followed that results in formation of the casein micelle. As a result of forming micelles, nutritious milk can be secreted and stored without causing either pathological calcification or amyloidosis of the mother's mammary tissue. The ability to sequester nanoclusters of amorphous calcium phosphate in a stable complex is not unique to caseins. It has been demonstrated using a number of noncasein secreted phosphoproteins and may be of general physiological importance in preventing calcification of other biofluids and soft tissues. Thus, competent noncasein phosphoproteins have similar patterns of phosphorylation and the same type of flexible, unfolded conformation as caseins. The ability to suppress amyloid fibril formation by forming an alternative amorphous aggregate is also not unique to caseins and underlies the action of molecular chaperones such as the small heat-shock proteins. The open structure of the protein matrix of casein micelles is fragile and easily perturbed by changes in its environment. Perturbations can cause the polypeptide chains to segregate into regions of greater and lesser density. As a result, the reliable determination of the native structure of casein micelles continues to be extremely challenging. The biological functions of caseins, such as their chaperone activity, are determined by their composition and flexible conformation and by how the casein polypeptide chains interact with each other. These same properties determine how caseins behave in the manufacture of many dairy products and how they can be used as functional ingredients in other foods. aBStraCtA typical casein micelle contains thousands of casein molecules, most of which form thermodynamically stable complexes with nanoclusters of amorphous calcium phosphate. Like many other unfolded proteins, caseins have an actual or potential tendency to assemble into toxic amyloid fibrils, particularly at the high concentrations found in milk. Fibrils do not form in milk because an alternative aggregation pathway is followed that results in formation of the casein micelle. As a result of forming micelles, nutritious milk can be secreted and stored without causing either pathological calcification or amyloidosis of the mother's mammary tissue. The ability to sequester nanoclusters of amorphous calcium phosphate in a stable complex is not unique to caseins. It has been demonstrated using a number of noncasein secreted phosphoproteins and may be of general physiological importance in preventing calcification of other biofluids and soft tissues. Thus, competent noncasein phosphoproteins have similar patterns of phosp...

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“…Some models have proposed arrangements of the proteins within the micelle as clusters or sub-micelles [16,25,45], but the physical arrangement is still subject to much debate [12,40]. One of the models of casein in milk is as a cluster of several hundred casein molecules, with the proteins arranged with a dense hydrophobic core, in which most of the hydrophobic parts of the casein molecules are buried, and a more loosely packed hydrophilic outer layer, containing most of the acidic (carboxylic and phosphoric) groups and some of the basic groups [47].…”

Section: Milk Componentsmentioning

confidence: 99%

Insolubility of milk powder products – A minireview

Baldwin

2010

Dairy Sci. Technol.

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-In this paper, the formation of insolubility in milk powder is described, and the factors affecting the reaction are discussed. The zone in which casein proteins are most sensitive to heat is in the moisture range that occurs during spray drying. The rate of reaction has been determined and shows differences of orders of magnitude with the moisture content. The effect of chemical reagents on the extent of reaction gives insights into the chemical bonds that inhibit hydration. Information on the drying of casein products and individual proteins is used to infer that the withdrawal of moisture from casein proteins and the concentration of divalent cations during drying lead to alterations in the conformation of proteins that have an adverse effect on their rehydration during reconstitution. Further work to fully characterise these effects is required.spray drying / powder / casein / insolubility / kineticsRésumé -Insolubilité des poudres laitières -une mini-revue. L'apparition de l'insolubilité des poudres laitières est décrite et les facteurs affectant cette réaction sont discutés dans cet article. La zone dans laquelle les caséines sont les plus sensibles à la chaleur se situe dans la gamme d'humidité intervenant au cours du procédé de séchage par atomisation. La vitesse de réaction a été déterminée et montre des différences d'ordres de grandeur des taux d'humidité. L'effet des réactifs chimiques sur l'étendue de la réaction donne un aperçu des liaisons chimiques qui inhibent l'hydratation. On peut déduire de l'information obtenue sur le séchage des caséines et des protéines individuelles que l'élimination de l'humidité des caséines et la concentration en cations divalents au cours du séchage conduisent à des modifications de la conformation des protéines qui peuvent avoir des effets négatifs sur leur réhydratation au cours de la reconstitution des poudres. Un travail ultérieur est nécessaire pour caractériser complètement ces effets.séchage par atomisation / poudre / caséine / insolubilité / cinétique

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The casein micelle: Historical aspects, current concepts and significance

Cited by 313 publications

References 71 publications

Caracterização eletroforética de proteínas e estabilidade do leite em vacas submetidas à restrição alimentar

Caracterização eletroforética de proteínas e estabilidade do leite em vacas submetidas à restrição alimentar

Invited review: Caseins and the casein micelle: Their biological functions, structures, and behavior in foods

Insolubility of milk powder products – A minireview

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