Heat-Induced Interactions of Whey Proteins and Casein Micelles with Different Concentrations of α-Lactalbumin and β-Lactoglobulin

1997 ◽  
Vol 45 (12) ◽  
pp. 4806-4813 ◽  
Author(s):  
Douglas G. Dalgleish ◽  
Lydia van Mourik ◽  
Milena Corredig
Keyword(s):  
Whey Proteins ◽  
Casein Micelles ◽  
Β Lactoglobulin

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.

High pressure treatment of bovine milk: effects on casein micelles and whey proteins

2004 ◽  
Vol 71 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Thom Huppertz ◽  
Patrick F Fox ◽  
Alan L Kelly
Keyword(s):  
High Pressure ◽  
Treatment Time ◽  
Whey Proteins ◽  
Bovine Milk ◽  
Casein Micelle ◽  
Pressure Treatment ◽  
Casein Micelles ◽  
High Pressure Treatment ◽  
Micelle Size ◽  
Β Lactoglobulin

Effects of high pressure (HP) on average casein micelle size and denaturation of α-lactalbumin (α-la) and β-lactoglobulin (β-lg) in raw skim bovine milk were studied over a range of conditions. Micelle size was not influenced by treatment at pressures <200 MPa, but treatment at 250 MPa increased micelle size by ∼25%, while treatment at [ges ]300 MPa irreversibly reduced it to ∼50% of that in untreated milk. The increase in micelle size after treatment at 250 MPa was greater with increasing treatment time and temperature and milk pH. Treatment times [ges ]2 min at 400 MPa resulted in similar levels of micelle disruption, but increasing milk pH to 7·0 partially stabilised micelles against HP-induced disruption. Denaturation of α-la did not occur [les ]400 MPa, whereas β-lg was denatured at pressures >100 MPa. Denaturation of α-la and β-lg increased with increasing pressure, treatment time and temperature and milk pH. The majority of denatured β-lg was apparently associated with casein micelles. These effects of HP on casein micelles and whey proteins in milk may have significant implications for properties of products made from HP-treated milk.

Disruption and reassociation of casein micelles during high pressure treatment: influence of whey proteins

2007 ◽  
Vol 74 (2) ◽  
pp. 194-197 ◽  
Author(s):  
Thom Huppertz ◽  
Cornelis G de Kruif
Keyword(s):  
High Pressure ◽  
Treatment Time ◽  
Light Transmission ◽  
Whey Proteins ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Β Lactoglobulin ◽  
Steric Stabilisation ◽  
Prolonged Holding

In the study presented in this article, the influence of added α-lactalbumin and β-lactoglobulin on the changes that occur in casein micelles at 250 and 300 MPa were investigated by in-situ measurement of light transmission. Light transmission of a serum protein-free casein micelle suspension initially increased with increasing treatment time, indicating disruption of micelles, but prolonged holding of micelles at high pressure partially reversed HP-induced increases in light transmission, suggesting reformation of micellar particles of colloidal dimensions. The presence of α-la and/or β-lg did not influence the rate and extent of micellar disruption and the rate and extent of reformation of casein particles. These data indicate that reformation of casein particles during prolonged HP treatment occurs as a result of a solvent-mediated association of the micellar fragments. During the final stages of reformation, κ-casein, with or without denatured whey proteins attached, associates on the surface of the reformed particle to provide steric stabilisation.

Kinetics of heat-induced whey protein denaturation and aggregation in skim milks with adjusted whey protein concentration

2005 ◽  
Vol 72 (3) ◽  
pp. 369-378 ◽  
Author(s):  
David J Oldfield ◽  
Harjinder Singh ◽  
Mike W Taylor
Keyword(s):  
Whey Protein ◽  
Protein Concentration ◽  
Protein Denaturation ◽  
Polyacrylamide Gel Electrophoresis ◽  
Whey Proteins ◽  
Pilot Scale ◽  
Casein Micelles ◽  
Reaction Orders ◽  
Β Lactoglobulin ◽  
Kinetics Of

Microfiltration and ultrafiltration were used to manufacture skim milks with an increased or reduced concentration of whey proteins, while keeping the casein and milk salts concentrations constant. The skim milks were heated on a pilot-scale UHT plant at 80, 90 and 120 °C. The heat-induced denaturation and aggregation of β-lactoglobulin (β-lg), α-lactalbumin (α-la) and bovine serum albumin (BSA) were quantified by polyacrylamide gel electrophoresis. Apparent rate constants and reaction orders were calculated for β-lg, α-la and BSA denaturation. Rates of β-lg, α-la and BSA denaturation increased with increasing whey protein concentration. The rate of α-la and BSA denaturation was affected to a greater extent than β-lg by the change in whey protein concentration. After heating at 120 °C for 160 s, the concentration of β-lg and α-la associated with the casein micelles increased as the initial concentration of whey proteins increased.

CPG-chromatography studies on the stability of casein micelles

1979 ◽  
Vol 46 (2) ◽  
pp. 313-316 ◽  
Author(s):  
Märtha Larsson-Raźnikiewicz ◽  
Elisabeth Almlöf ◽  
Bo Ekstrand
Keyword(s):  
Freeze Drying ◽  
Whey Proteins ◽  
Skim Milk ◽  
Casein Micelles ◽  
Controlled Pore Glass ◽  
Milk Serum ◽  
Colloidal Calcium Phosphate ◽  
Pore Glass ◽  
The Stability ◽  
Β Lactoglobulin

SUMMARYCasein micelles fractionated on controlled pore glass (CPG-10/3000) were shown to be stable by recycling experiments. Only minor effects on the size distribution of the casein micelles were found after heating skim-milk to 100 °C for 10 min, or freeze-drying skim-milk at – 70 °C followed by resuspension in the synthetic milk serum of Jenness & Koops (1962). The heating caused some whey proteins (β-lactoglobulin) to enter the micelle fractions while the freeze-drying caused some of the largest micelles to disrupt. In colloidal calcium phosphate-free skim-milk prepared according to Pyne & McGann (1960) all the micelles appeared to dissociate into monomeric caseins.

Heat induced gelation of acid milk: balance between weak and covalent bonds

2003 ◽  
Vol 70 (2) ◽  
pp. 253-256 ◽  
Author(s):  
Olivier Surel ◽  
Marie-Hélène Famelart
Keyword(s):  
Protein Interactions ◽  
Whey Proteins ◽  
High Heat ◽  
Heat Treatments ◽  
Protein Protein Interactions ◽  
Casein Micelles ◽  
Covalent Bonds ◽  
Disulphide Bonds ◽  
Initial Stage ◽  
Β Lactoglobulin

Gelation of acidified milk at pH[ges ]5, after heat treatments is a well known phenomenon, due to the precipitation of whey proteins, and especially β-lactoglobulin onto κ-casein (Sawyer, 1969). High heat treatments cause denaturation of whey proteins which associate with κ-casein through disulphide interchange reactions (Hill, 1989). Since their charge is reduced, the denatured proteins associated with casein micelles become susceptible to aggregation when milk is then acidified, which promotes enhanced protein–protein interactions (Lucey et al. 1997). The gelation phenomenon involves disulphide bonds (Hashizume & Sato, 1988; Goddard, 1996) which are responsible for the gel firmness (Goddard, 1996). However, other interactions between proteins can occur, such as hydrogen and hydrophobic bonds, especially at the initial stage of interactions (Haque et al. 1987; Haque & Kinsella, 1988; Jang & Swaisgood, 1990). It is therefore relevant to investigate a possible contribution of weak linkages to the gel structure and firmness.

The dynamics of individual whey protein concentrations in cows’ mammary secretions during the colostral and early lactation periods

2018 ◽  
Vol 86 (1) ◽  
pp. 88-93 ◽  
Author(s):  
Raquel F.S. Raimondo ◽  
Juliana S.P. Ferrão ◽  
Samantha I. Miyashiro ◽  
Priscila T. Ferreira ◽  
João Paulo E. Saut ◽  
...  
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Whey Proteins ◽  
Total Proteins ◽  
Mature Milk ◽  
Rennet Coagulation ◽  
Sds Page ◽  
Different Types ◽  
Biuret Method ◽  
Jersey Cows ◽  
Β Lactoglobulin

AbstractThe bovine whey consists of more than 200 different types of proteins, of which β-lactoglobulin, α-lactalbumin, serum albumin, immunoglobulins and lactoferrin predominate. However, their concentrations are not stable due to the existence of protein dynamics during a transition from colostrum secretion to mature milk. To evaluate the dynamics of whey proteins of Jersey cows during a colostral phase and first month of lactation and an influence of the number of lactations, 268 milk samples from 135 Jersey cows were selected through a clinical evaluation. Whey was obtained by rennet coagulation of the mammary secretion. The concentration of total proteins was determined by the biuret method and their fractions were identified by 12% dodecyl sulfate-polyacrylamide gel electrophoresis (12% SDS-PAGE). Maximum concentrations of all protein fractions were observed in the first 12 h of lactation, reducing over the course of the study. Modification of the protein predominance was also observed. The transition from colostrum secretion to milk occurred between 24 and 72 h postpartum. There was an influence of the number of lactations on the dynamics of whey proteins, indicating that multiparous cows had better immunological and nutritional quality when compared to primiparous cows.

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