scholarly journals The influence of high temperatures on milk proteins

2002 ◽  
Vol 56 (3) ◽  
pp. 123-132 ◽  
Author(s):  
Ognjen Macej ◽  
Snezana Jovanovic ◽  
Jelena Djurdjevic-Denin
Keyword(s):  
High Temperatures ◽  
Milk Fat ◽  
Protein Denaturation ◽  
Whey Proteins ◽  
Milk Proteins ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Rennet Coagulation ◽  
Milk Fat Globule ◽  
Rennet Casein

High temperatures Induce certain changes in milk constituents, but the degree of these changes depends on both the temperature and time of heat treatment. The most pronounced changes take place in milk proteins. The forewarming of milk causes an increase in acidity, the precipitation of soluble Ca-phosphate, whey protein denaturation and coagulation, as well as the interaction with casein micelles, the Maillard browning reaction, the dephosphorylation of casein, the hydrolysis of casein micelles, changes in whey proteins, an extension of the rennet coagulation time and an exchange of the rheological properties of the acid and rennet casein gels, changes in the zeta-potential and casein micelle hydration, the interaction between the milk proteins and proteins of milk fat globule membrane.

Milk-fat globule membrane in homogenized cream

1978 ◽  
Vol 45 (2) ◽  
pp. 197-208 ◽  
Author(s):  
Donald F. Darling ◽  
David W. Butcher
Keyword(s):  
Milk Fat ◽  
Polyacrylamide Gel Electrophoresis ◽  
Whey Proteins ◽  
Dominant Group ◽  
Casein Micelles ◽  
Milk Fat Globule Membrane ◽  
Milk Fat Globule ◽  
Fat Globule ◽  
Subsequent Storage ◽  
Interfacial Membrane

SummaryThe proteins of the milk-fat globule membrane in homogenized cream have been studied using polyacrylamide-gel electrophoresis and electron microscopy. The effects of pasteurization and subsequent storage of the homogenized cream on the strength and composition of the membrane have also been investigated. Caseins and undenatured whey proteins are adsorbed to the fat–serum interface during homogenization; the caseins are the more dominant group, but with no apparent preference for any individual protein. After homogenization, but before pasteurization, whey proteins are more easily removed by washing than are the casein components. After subsequent pasteurization, and on storage, whey proteins become more tightly bound and are no longer readily removed by washing. Electron micrographs showed that the interfacial membrane between fat droplets and the serum phase consists of a protein composite material containing casein micelles, casein micellar sub-units and molecular, or non-micellar protein.

Cryo-SEM images of native milk fat globule indicate small casein micelles are constituents of the membrane

RSC Advances ◽  
2014 ◽  
Vol 4 (90) ◽  
pp. 48963-48966 ◽  
Author(s):  
Jie Luo ◽  
Zi Wei Wang ◽  
Fang Wang ◽  
Hao Zhang ◽  
Jiang Lu ◽  
...  
Keyword(s):  
Milk Fat ◽  
Whey Proteins ◽  
Casein Micelles ◽  
Sem Images ◽  
Schematic Representation ◽  
Milk Fat Globule Membrane ◽  
Milk Fat Globule ◽  
Fat Globule

Schematic representation of the native milk fat globule membrane: casein micelles and whey proteins on the surface of the membrane.

Chemical changes in bovine milk fat globule membrane caused by heat treatment and homogenization of whole milk

2002 ◽  
Vol 69 (4) ◽  
pp. 555-567 ◽  
Author(s):  
SUNG JE LEE ◽  
JOHN W. SHERBON
Keyword(s):  
Heat Treatment ◽  
Membrane Proteins ◽  
Milk Fat ◽  
Whey Proteins ◽  
Bovine Milk ◽  
Chemical Changes ◽  
Milk Fat Globule Membrane ◽  
Whole Milk ◽  
Milk Fat Globule ◽  
Fat Globule

The effects of heat treatment and homogenization of whole milk on chemical changes in the milk fat globule membrane (MFGM) were investigated. Heating at 80 °C for 3–18 min caused an incorporation of whey proteins, especially β-lactoglobulin (β-lg), into MFGM, thus increasing the protein content of the membrane and decreasing the lipid. SDS-PAGE showed that membrane glycoproteins, such as PAS-6 and PAS-7, had disappeared or were weakly stained in the gel due to heating of the milk. Heating also decreased free sulphydryl (SH) groups in the MFGM and increased disulphide (SS) groups, suggesting that incorporation of β-lg might be due to association with membrane proteins via disulphide bonds. In contrast, homogenization caused an adsorption of caseins to the MFGM but no binding of whey proteins to the MFGM without heating. Binding of caseins and whey proteins and loss of membrane proteins were not significantly different between milk samples that were homogenized before and after heating. Viscosity of whole milk was increased when milk was treated with both homogenization and heating.

scholarly journals Whey proteins modify the phase transition of milk fat globule phospholipids

1999 ◽  
Vol 79 (2) ◽  
pp. 217-228 ◽  
Author(s):  
Eric Dufour ◽  
Muriel Subirade ◽  
Franck Loupil ◽  
Alain Riaublanc
Keyword(s):  
Phase Transition ◽  
Milk Fat ◽  
Whey Proteins ◽  
Milk Fat Globule ◽  
Fat Globule

scholarly journals Increasing the biological value of the curd product

2018 ◽  
Vol 80 (3) ◽  
pp. 124-127
Author(s):  
E. I. Dobriyan ◽  
A. M. Ilina ◽  
T. A. Medvedeva
Keyword(s):  
Carbohydrate Metabolism ◽  
Milk Fat ◽  
Nutritive Value ◽  
Wide Spectrum ◽  
Whey Proteins ◽  
Milk Proteins ◽  
The Body ◽  
Diabetic Patients ◽  
Biological Value ◽  
Test Intensity

The article is devoted to the improvement of quark product biological value in order to impart the properties adequate to specifity and nutrient status for the group of population with abnormal carbohydrate metabolism. Diabetes comprises the most widespread chronic diseases in the world. The reason for the number of diabetic patients growth bears the complex character but this growth is conditioned mainly by malnutrition. Correctly chosen diet adequate to the level and character of metabolic disorders is the important prophylactic factor. Milk products among which quark and quark products due to high amount of easily digestible protein are very Important in nutrition of the patients suffering from abnormal carbohydrate metabolism. The marketing analysis of this group nutritive value presented in the marked has been carried out. The obtained results show that the manufactures quark products are characterized by low amount of crude protein (from 4.5 to 6.0%) and high carbohydrates content ( from 13,0 to 18.0%) including sucrose (from 7,5 to 12,0%. One of the main requirements to dietetic therapy of the patients suffering from diabetes is drastic restriction and exclusion from food allowance easily digestible refined carbohydrates. The aim of the work is to improve biological value of the quark product by replacement of sucrose by stevia and enrichment it by whey protein. Among sugar substitute of natural origin is stevia, which besides the ability to reduce sugar possesses the wide spectrum of positive physiological impact on the body. The influence of milk components on the expressed after-taste of stevia and the possibility to level it has been studied. It was stated that protein has no impact on stevia after-taste but milk fat partially levels metallic taste and promotes the test intensity. It was stated that the best product organoleptic indices were fixed after introduction of 0.027% of stevia. Milk proteins are food irreplaceable components and mainly whey proteins characterized by high biological value conditioned by their specificity and balanced amino acid composition. But meanwhile commercial samples of quark products contained not more than 0,05% of whey proteins . The possibility to improve the biological value of the product by enrichment with whey proteins has been studied.

Gelation of casein-whey mixtures: effects of heating whey proteins alone or in the presence of casein micelles

2001 ◽  
Vol 68 (3) ◽  
pp. 471-481 ◽  
Author(s):  
CATHERINE SCHORSCH ◽  
DEBORAH K. WILKINS ◽  
MALCOLM G. JONES ◽  
IAN T. NORTON
Keyword(s):  
Heat Treatment ◽  
Whey Protein ◽  
Protein Denaturation ◽  
Whey Proteins ◽  
Treatment Sequence ◽  
Gel Properties ◽  
Casein Micelles ◽  
Gelation Kinetics ◽  
Milk Gelation

The aim of the present work was to investigate the role of whey protein denaturation on the acid induced gelation of casein. This was studied by determining the effect of whey protein denaturation both in the presence and absence of casein micelles. The study showed that milk gelation kinetics and gel properties are greatly influenced by the heat treatment sequence. When the whey proteins are denatured separately and subsequently added to casein micelles, acid-induced gelation occurs more rapidly and leads to gels with a more particulated microstructure than gels made from co-heated systems. The gels resulting from heat-treatment of a mixture of pre-denatured whey protein with casein micelles are heterogeneous in nature due to particulates formed from casein micelles which are complexed with denatured whey proteins and also from separate whey protein aggregates. Whey proteins thus offer an opportunity not only to control casein gelation but also to control the level of syneresis, which can occur.

Heat stability of milk: pH-dependent dissociation of micellar κ-casein on heating milk at ultra high temperatures

1985 ◽  
Vol 52 (4) ◽  
pp. 529-538 ◽  
Author(s):  
Harjinder Singh ◽  
Partick F. Fox
Keyword(s):  
Whey Protein ◽  
Whey Proteins ◽  
Heat Stability ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Ph Profile ◽  
Ph Values ◽  
Maximum Stability ◽  
Β Lactoglobulin ◽  
Maximum Minimum

SUMMARYPreheating milk at 140 °C for 1 min at pH 6·6, 6·8, 7·0 or 7·2 shifted the heat coagulation time (HCT)/pH profile to acidic values without significantly affecting the maximum stability. Whey proteins (both β-lactoglobulin and α-lactalbumin) co-sedimented with the casein micelles after heating milk at pH < 6·9 and the whey protein-coated micelles, dispersed in milk ultrafiltrate, showed characteristic maxima–minima in their HCT/pH profile. Heating milk at higher pH values (> 6·9) resulted in the dissociation of whey proteins and κ-casein-rich protein from the micelles and the residual micelles were unstable, without a maximum–minimum in the HCT/pH profile. Preformed whey protein–casein micelle complexes formed by preheating (140 °C for 1 min) milk at pH 6·7 dissociated from the micelles on reheating (140 °C for 1 min) at pH > 6·9. The dissociation of micellar-κ-casein, perhaps complexed with whey proteins, may reduce the micellar zeta potential at pH ≃ 6·9 sufficiently to cause a minimum in the HCT/pH profile of milk.

High-pressure treatment of milk: effects on casein micelle structure and on enzymic coagulation

2000 ◽  
Vol 67 (1) ◽  
pp. 31-42 ◽  
Author(s):  
ERIC C. NEEDS ◽  
ROBERT A. STENNING ◽  
ALISON L. GILL ◽  
VICTORIA FERRAGUT ◽  
GILLIAN T. RICH
Keyword(s):  
Whey Proteins ◽  
Skim Milk ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Dense Networks ◽  
Protein Levels ◽  
Micelle Structure ◽  
Milk Casein ◽  
Β Lactoglobulin ◽  
Gel Network

High isostatic pressures up to 600 MPa were applied to samples of skim milk before addition of rennet and preparation of cheese curds. Electron microscopy revealed the structure of rennet gels produced from pressure-treated milks. These contained dense networks of fine strands, which were continuous over much bigger distances than in gels produced from untreated milk, where the strands were coarser with large interstitial spaces. Alterations in gel network structure gave rise to differences in rheology with much higher values for the storage moduli in the pressure-treated milk gels. The rate of gel formation and the water retention within the gel matrix were also affected by the processing of the milk. Casein micelles were disrupted by pressure and disruption appeared to be complete at treatments of 400 MPa and above. Whey proteins, particularly β-lactoglobulin, were progressively denatured as increasing pressure was applied, and the denatured β-lactoglobulin was incorporated into the rennet gels. Pressure-treated micelles were coagulated rapidly by rennet, but the presence of denatured β-lactoglobulin interfered with the secondary aggregation phase and reduced the overall rate of coagulation. Syneresis from the curds was significantly reduced following treatment of the milk at 600 MPa, probably owing to the effects of a finer gel network and increased inclusion of whey protein. Levels of syneresis were more similar to control samples when the milk was treated at 400 MPa or less.

Recent advances in the destabilization of dairy emulsions

1982 ◽  
Vol 49 (4) ◽  
pp. 695-712 ◽  
Author(s):  
Donald F. Darling
Keyword(s):  
Milk Fat ◽  
Quantitative Measure ◽  
Major Protein ◽  
Casein Micelle ◽  
Emulsion Droplets ◽  
Aggregation Processes ◽  
Constant Shear Stress ◽  
Adsorption Processes ◽  
Milk Fat Globule ◽  
Fat Globule

SUMMARYDestabilization of emulsion droplets is described in terms of flocculation, coalescence and adsorption processes, and then discussed with reference to various technological aspects of dairy emulsions. A semi-quantitative measurement of homogenization-induced flocculation of cream is described using measurements on the time-dependent decrease in viscosity that occurs during shear. The whipping of cream is discussed in terms of the adsorption of fat droplets to air bubbles and the formation of a fat particle network with the fat directly in contact with air. The whipping of homogenized creams is shown to be dependent upon the structure of the newly formed milk fat globule membrane. Since the major protein component of the membrane is casein, any change in casein micelle stability is reflected in the whipping properties of the cream.The presence of crystalline fat within emulsion droplets is essential for many destabilization processes. Fat crystals pierce the film between 2 approaching interfaces, thus leading to aggregation. The contact angle between fat crystal, oil and aqueous phase can be used to describe the susceptibility of an emulsion to destabilize.A quantitative measure of emulsion destabilization under shear is described kinetically in terms of reversible flocculation followed by coalescence. The measurement of emulsion viscosity as a function of time at constant shear stress is used to monitor the aggregation processes and the 3 rate constants evaluated by computer curve fitting.

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