Disruption and reassociation of casein micelles under high pressure

High pressure (HP) treatment affects many constituents of milk (for reviews see Huppertz et al. 2002; Needs, 2002); particular in the properties of casein micelles in HP-treated milk differ considerably from their counterparts in untreated milk. In milk treated at 100–200 MPa, average casein micelle size differs little from that of untreated milk (Needs et al. 2000a; Huppertz et al. 2004a; Regnault et al. 2004; Anema et al. 2005), but micelle size in milk treated at 250 MPa for [ges ]15 min is considerably higher than in untreated milk, probably due to HP-induced aggregation of casein micelles (Huppertz et al. 2004a,b; Regnault et al. 2004); after treatment at 300–800 MPa, micelle size is ~50% lower than that in untreated milk (Needs et al. 2000a; Huppertz et al. 2004a,b; Anema et al. 2005). HP-induced changes in average casein micelle size are irreversible on subsequent storage, except for the increase in micelle size after treatment at 250 MPa (Huppertz et al. 2004a).

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

Journal of Dairy Research ◽

10.1017/s002202990300640x ◽

2004 ◽

Vol 71 (1) ◽

pp. 97-106 ◽

Cited By ~ 142

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.

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Effects of high pressure on some constituents and properties of buffalo milk

Journal of Dairy Research ◽

10.1017/s0022029905000701 ◽

2005 ◽

Vol 72 (2) ◽

pp. 226-233 ◽

Cited By ~ 16

Author(s):

Thom Huppertz ◽

Mathias R Zobrist ◽

Therese Uniacke ◽

Vivekk Upadhyat ◽

Patrick F Fox ◽

...

Keyword(s):

High Pressure ◽

Buffalo Milk ◽

Casein Micelle ◽

Coagulation Time ◽

Casein Micelles ◽

Rennet Coagulation ◽

Micelle Size ◽

Significant Difference ◽

Β Lactoglobulin

In this study, effects of high pressure (HP) on some constituents and properties of buffalo milk were examined. HP treatment at 100–600 MPa for 30 min affected casein micelle size only slightly, whereas treatment at 800 MPa increased it by ~35%. Levels of non-micellar αs1- and β-caseins were increased by treatment [ges ]250 MPa, and were highest after treatment at 400–800 MPa. The level of non-micellar calcium increased with increasing pressure up to 600 MPa. The L*-value of the milk decreased gradually with increasing pressure, from ~82 for untreated milk to ~65 for milk treated at 800 MPa. Milk pH was increased by ~0·07 units after treatment at 100–800 MPa, with no significant difference between treatment pressures. Denaturation of α-lactalbumin occurred at pressures [ges ]400 MPa, and reached >90% after treatment at 800 MPa, whereas β-lactoglobulin (β-lg) was denatured >100 MPa, reaching ~100% after treatment at 400 MPa; after treatment [ges ]400 MPa, all β-lg was associated with the casein micelles. The rennet coagulation time of buffalo milk increased with increasing pressure, whereas the strength of the coagulum formed decreased after treatment at 250–800 MPa. Overall, HP treatment affected many constituents and properties of buffalo milk; some of these effects have also been observed in the milk from other species, but the extent of the effects, and the pressure at which they occurred, differed considerably.

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Association of casein micelle size and enzymatic curd strength and dry matter curd yield

Ciência Rural ◽

10.1590/0103-8478cr20180409 ◽

2019 ◽

Vol 49 (3) ◽

Author(s):

Denise Ribeiro de Freitas ◽

Fernando Nogueira de Souza ◽

Jamil Silvano de Oliveira ◽

Diêgo dos Santos Ferreira ◽

Cristiane Viana Guimarães Ladeira ◽

...

Keyword(s):

Fixed Effects ◽

Dry Matter ◽

Linear Models ◽

Favorable Effect ◽

Casein Micelle ◽

Casein Micelles ◽

Micelle Size ◽

Milk Protein Content ◽

Bulk Tank ◽

Cheese Production

ABSTRACT: The aim of the present study was to explore the association between milk protein content and casein micelle size and to examine the effects of casein micelle size on enzymatic curd strength and dry matter curd yield using reduced laboratory-scale cheese production. In this research, 140 bulk tank milk samples were collected at dairy farms. The traits were analyzed using two linear models, including only fixed effects. Smaller micelles were associated with higher κ-casein and lower αs-casein contents. The casein micellar size (in the absence of the αs-casein and κ-casein effects) did not affect the enzymatic curd strength; however, smaller casein micelles combined with higher fat, lactose, casein and κ-casein contents exhibited a favorable effect on the dry matter curd yield. Overall, results of the present study provide new insights into the importance of casein micelle size for optimizing cheese production.

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Influence of homogenization of concentrated milks on the structure and properties of rennet curds

Journal of Dairy Research ◽

10.1017/s0022029900023177 ◽

1983 ◽

Vol 50 (3) ◽

pp. 341-348 ◽

Cited By ~ 70

Author(s):

Margaret L. Green ◽

Richard J. Marshall ◽

Frank A. Glover

Keyword(s):

Fatty Acid ◽

Free Fatty Acid ◽

Size Distribution ◽

Casein Micelle ◽

Structure And Properties ◽

Moisture Retention ◽

Casein Micelles ◽

Micelle Size ◽

Whole Milk ◽

Milk Casein

SummaryWhole milk was concentrated by ultrafiltration in a plant causing some homogenization of the fat. Comparisons were made with milk concentrated in a plant causing little homogenization and with milk homogenized conventionally. None of the processes appreciably affected the casein micelle size distribution. On rennet treatment of homogenized milk, casein micelle aggregation occurred more slowly, the protein network in the curd was less coarse and the rate of whey loss was reduced, compared with non-homogenized milk at the same concentration. In using concentrated milks for cheesemaking homogenization improved the composition of Cheddar cheese, because of increased fat and moisture retention, but curd fusion was poorer. Some aspects of the texture of the mature cheeses were improved, but the free fatty acid levels were higher. Values for the firmness of curds, formed from milks processed in different ways, did not relate to the extent of aggregation of the casein micelles. It is suggested that the complete cheesemaking process is driven by the tendency of the casein to aggregate.

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The structure of casein micelles between pH 5·5 and 6·7 as determined by light-scattering, electron microscopy and voluminosity experiments

Journal of Dairy Research ◽

10.1017/s0022029900028946 ◽

1989 ◽

Vol 56 (3) ◽

pp. 463-470 ◽

Cited By ~ 21

Author(s):

Henk J. Vreeman ◽

Bas W. van Markwijk ◽

Paula Both

Keyword(s):

Electron Microscopy ◽

Light Scattering ◽

Comparative Data ◽

Casein Micelle ◽

Protein Matrix ◽

Casein Micelles ◽

Inelastic Light Scattering ◽

Micelle Size

SummaryHydrodynamic radii from inelastic light-scattering experiments and radii of gyration from Zimm plots give an indication of the change of average casein micelle size when the pH is changed. Combination of the results of both types of measurements gives information on changes in the micelle protein matrix, i.e. changes in the voluminosity.The voluminosity was also determined by the pellet method and by electron microscopy which also provided comparative data on size parameters.

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THE PHYSICAL PROPERTIES OF THE CASEIN IN SOLUTION: EFFECT OF ULTRA-HIGH PRESSURE

Food systems ◽

10.21323/2618-9771-2018-1-3-4-12 ◽

2018 ◽

Vol 1 (3) ◽

pp. 4-12

Author(s):

Roman O. Budkevich ◽

Anastasia I. Eremina ◽

Ivan A. Evdokimov ◽

Nikita M. Fedortsov ◽

Alexey A. Martak ◽

...

Keyword(s):

High Pressure ◽

Hydrodynamic Radius ◽

Physical Property ◽

Tryptophan Fluorescence ◽

Raw Milk ◽

Correlation Spectroscopy ◽

Casein Micelle ◽

Pressure Treatment ◽

Casein Micelles ◽

Large Particles

The aim of this work was to study the effect of pressure (50; 90; 160; 250; 350 MPa) on a physical property of casein micelle: hydrodynamic radius, tyrosine and tryptophan fluorescence and IR spectra characteristics. According to photon-correlation spectroscopy, the average hydrodynamic radius of the casein micelle was 128 nm, increasing at 50 MPa to 467 nm with the formation of conglomerates. Further increase of pressure led to the formation of two fractions of particles, differing in hydrodynamic radius. At a pressure of 350 MPa, an average radius of 75 % of particles was 121 nm. Comparison of hydrodynamic radius and tyrosine fluorescence revealed a decrease in the intensity of the glow with an increase in the proportion of large particles and an increase in the radiation in the solution with a decrease of the micelles size. The increase of casein fluorescence by tryptophan and its decrease by tyrosine indicate a change in the conformation of protein molecules during pressure treatment. FTIR spectroscopy revealed a change in the intensity of the optical density in the range of amide I, amide II and valence bonds of tyrosine, confirming the absence of new bonds. The obtained physical data indicate a change in the structure of casein micelles with an increase in the proportion (25 %) of large particles after the action of high pressure (350mpa), which should be taken into account in milk processing. The fluorescence of casein during pressure treatment is a poorly investigated physical indicator and can be important for the processing of raw milk.

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

Journal of Dairy Research ◽

10.1017/s0022029906002263 ◽

2007 ◽

Vol 74 (2) ◽

pp. 194-197 ◽

Cited By ~ 21

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.

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Electrophoretic mobility of casein micelles

Journal of Dairy Research ◽

10.1017/s0022029900017477 ◽

1979 ◽

Vol 46 (3) ◽

pp. 441-451 ◽

Cited By ~ 29

Author(s):

Donald F. Darling ◽

John Dickson

Keyword(s):

Electrophoretic Mobility ◽

Moving Boundary ◽

Ionic Composition ◽

Skim Milk ◽

Casein Micelle ◽

Casein Micelles ◽

Zeta Potentials ◽

Micelle Structure ◽

Increase With Increase ◽

Micelle Size

SummaryA simplified moving boundary electrophoresis technique has been developed for the measurement of the electrophoretic mobility of casein micelles. The zeta potentials of casein micelles from different skim-milk samples were calculated using Henry's equation and shown to decrease with decrease in pH between pH 6.9 and 5.3 and to increase with increase in temperature between 10 and 45 °C. Neither severe heat treatment (up to 135 °C for 51 min) nor centrifugal fractionation of micelles into different micelle size ranges had any significant effect on zeta potential. The ionic composition of the serum phase has been shown to be extremely important in determining the electrophoretic mobility. Casein micelles electrophoresed through milk ultrafiltrate consistently gave a lower mobilities than the same micelles centrifuged through milk centrifugate. The results are discussed in relation to present theories of casein micelle structure; these theories do not accommodate all of the observations.

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