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Abstract
SummaryThe effects of decreasing pH and micellar calcium concentrations of reconstituted skim milk and caseinate solution were studied by 1H and 17O NMR spectroscopy. The proton transverse relaxation rate 1/T2 of skim milk decreased as the pH decreased, reaching a minimum at pH 5·3. However, as the pH fell sodium caseinate solution showed a continuous increase in 1/T2, with no minimum. Analysis of proton relaxation as a function of the interpulse time in the CPMG (Carr-Purcell-Meiboom-Gill) sequence demonstrated that both the proton exchange mechanism and ‘bound’ water contributed to proton relaxation in skim milk. The study of 17O relaxation rate as a function of pH confirmed the change in protein hydration upon acidification. Increasing the amount of EDTA showed that the proton transverse relaxation rate of skim milk decreased until a plateau was reached when the micellar calcium was totally solubilized. With excess EDTA the relaxation rates of skim milk and caseinate solution were identical. A strong correlation was also found between the pH dependent relaxation rate and the solubilization of micellar phosphorus as detected by 31P NMR. Together, these results suggested that aggregation of caseins by calcium and colloidal calcium phosphate is mainly responsible for the excess hydration in skim milk micelles.
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102
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Abstract
SummaryChanges in heat stability and Ca2+activity of recombined concentrated milk (18% solids non-fat:8% fat) induced by the additions of 0·011–0·217 mol phosphate/kg skim milk solids (SMS), 0·022–0·217 mol citrate/kg SMS, 0·011–0·022 mol Ca/kg SMS and 0·016–0·067 mol EDTA/kg SMS were evaluated. Heat stability was assessed using an objective method which involved determination of viscosity after heating under controlled conditions. Low levels of added phosphate and citrate generally effected an acid shift of the viscosity–pH profile, while higher levels caused a broadening of the profile. Addition of CaCl2at a level of 0·011 mol/kg SMS resulted in a narrowing of the viscosity–pH curve; additions of higher levels resulted in a non-heat stable recombined milk concentrate. EDTA also caused a narrowing of the viscosity–pH curve. The results highlight the importance of pH control for effective stabilization of recombined milk concentrates by additions of phosphate and citrate.
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103
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Abstract
SummaryThe effects of heat treatment and subsequent acidification of milk on the distribution of proteins, Ca and Pi, between the serum and micellar phases were examined using ultracentrifugation. After heating milk at 85 °C for 10 min, and storing for 22 h at 4, 20 or 30 °C, there was a marked increase in the concentration of κ-casein in the serum. At 4 and 20 °C there was also slightly more β-casein in the serum from heat-treated milk than in that from the corresponding raw milk. The whey proteins were extensively denatured, and were almost equally distributed between the supernatants and micellar pellets. After storage for 22 h the distribution of Ca and Pibetween soluble and colloidal phases in heat-treated milk was similar to that in raw milk. After acidifying heat-treated milk by the addition of glucono-δ-lactone and storing for 22 h at 4, 20 or 30 °C there was progressive solubilization of colloidal calcium phosphate with decreasing pH, and at pH 5·0 almost all of the Ca and Piwas present in the serum. At 20 °C, and even more so at 4 °C, serum concentrations of the individual caseins increased considerably with decreasing pH, reaching maximum levels of about 25 and 40% of the total casein at pH 5·7 and 5·5 respectively, and then decreasing rapidly at lower pH. Compared with raw milk, maximum dissociation in heat-treated milks stored at 4 and 20 °C occurred at higher pH, and the overall levels of dissociation of individual caseins from the micelles were lower. At 30 °C, the concentrations of individual caseins in the serum of heat-treated milk decreased steadily as the pH was reduced, and did not show the slight increase found previously for raw milk. The role of the denatured whey proteins in interacting with κ-casein and in promoting aggregation of the micelles on acidification is discussed.
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104
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Abstract
SummaryMeasurements of the zeta potential and particle size of casein micelles in skim milk suspensions at natural and lower pH have been made using the technique of electroacoustics. This technique requires no dilution or change of environment of the casein micelles. The zeta potential obtained at natural pH for a commercial skim milk suspension was −18 mV; it became less negative with decreasing pH. The median particle size observed at natural pH for a commercial skim milk suspension was 0·2 εm, in good agreement with previously reported values. The particle size increased as the pH was decreased.
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105
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Famelart MH, Gauvin G, Pâquet D, Brulé G. Acid gelation of colloidal calcium phosphate-depleted preheated milk. ACTA ACUST UNITED AC 2009. [DOI: 10.1051/dst/2009014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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106
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Semenova MG, Belyakova LE, Polikarpov YN, Antipova AS, Dickinson E. Light scattering study of sodium caseinate+dextran sulfate in aqueous solution: Relationship to emulsion stability. Food Hydrocoll 2009. [DOI: 10.1016/j.foodhyd.2008.06.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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107
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108
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Renan M, Guyomarc'h F, Arnoult-Delest V, Pâquet D, Brulé G, Famelart MH. Rheological properties of stirred yoghurt as affected by gel pH on stirring, storage temperature and pH changes after stirring. Int Dairy J 2009. [DOI: 10.1016/j.idairyj.2008.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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109
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MOON JEONGHAN, HONG YOUNHO, HUPPERTZ THOM, FOX PATRICKF, KELLY ALANL. Properties of casein micelles cross-linked by transglutaminase. INT J DAIRY TECHNOL 2009. [DOI: 10.1111/j.1471-0307.2008.00442.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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110
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Takeuchi KP, Cunha RL. Influence of ageing time on sodium caseinate gelation induced by glucono-δ-lactone at different temperatures. ACTA ACUST UNITED AC 2008. [DOI: 10.1051/dst:2008031] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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111
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ANEMA SKELTEG. EFFECT OF TEMPERATURE AND RATE OF ACIDIFICATION ON THE RHEOLOGICAL PROPERTIES OF ACID SKIM MILK GELS. J FOOD PROCESS PRES 2008. [DOI: 10.1111/j.1745-4549.2008.00230.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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112
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Martin G, Williams R, Choong C, Lee B, Dunstan D. Comparison of rennet gelation using raw and reconstituted skim milk. Int Dairy J 2008. [DOI: 10.1016/j.idairyj.2008.05.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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113
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114
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Mezdour S, Boyaval P, Korolczuk J. Solubility of αS1-, β- and κ-casein in water-ethanol solutions. ACTA ACUST UNITED AC 2008. [DOI: 10.1051/dst:2008001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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115
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Stability of casein micelles subjected to CO2 reversible acidification: Impact of carbonation temperature and chilled storage time. Int Dairy J 2008. [DOI: 10.1016/j.idairyj.2007.07.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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116
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Augustin MA, Clarke PT. Skim milk powders with enhanced foaming and steam-frothing properties. ACTA ACUST UNITED AC 2008. [DOI: 10.1051/dst:2007012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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117
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Pitkowski A, Nicolai T, Durand D. Scattering and Turbidity Study of the Dissociation of Casein by Calcium Chelation. Biomacromolecules 2007; 9:369-75. [DOI: 10.1021/bm7006899] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anne Pitkowski
- Polymères, Colloïdes, Interfaces, UMR CNRS, Université du Maine, 72085 le Mans Cedex 9, France
| | - Taco Nicolai
- Polymères, Colloïdes, Interfaces, UMR CNRS, Université du Maine, 72085 le Mans Cedex 9, France
| | - Dominique Durand
- Polymères, Colloïdes, Interfaces, UMR CNRS, Université du Maine, 72085 le Mans Cedex 9, France
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118
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Horne DS, Anema S, Zhu X, Nicholas KR, Singh H. A lactational study of the composition and integrity of casein micelles from the milk of the tammar wallaby (Macropus eugenii). Arch Biochem Biophys 2007; 467:107-18. [PMID: 17884009 DOI: 10.1016/j.abb.2007.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Accepted: 08/03/2007] [Indexed: 10/22/2022]
Abstract
The amount of casein found in the milk of the tammar wallaby increases as lactation progresses. The increase is due to increasing amounts of beta-casein; the alpha-casein remains largely constant. The alpha-casein is the more highly phosphorylated; the most abundant form is the 10-P, throughout lactation. The level of phosphorylation of beta-casein shifts to lower average values in late lactation, possibly indicating the enzymatic reaction is overloaded by the increasing amounts of beta-casein. Unlike bovine casein micelles, the wallaby micelles are not completely disrupted at pH 7.0 by sequestration of their calcium content with ethylene diamine tetraacetic acid (EDTA). Complete disruption only follows the addition of sodium dodecyl sulphate, indicating considerably greater importance for hydrophobic bonds in maintaining their integrity. This micellar behaviour indicates that, despite the evolutionary divergence of marsupials millennia ago, the caseins of wallaby milk assemble into micelles in much the same fashion as in bovine milk.
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119
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Raouche S, Dobenesque M, Bot A, Lagaude A, Cuq JL, Marchesseau S. Stability of casein micelle subjected to reversible CO2 acidification: Impact of holding time and chilled storage. Int Dairy J 2007. [DOI: 10.1016/j.idairyj.2006.11.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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120
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Canabady-Rochelle LS, Sanchez C, Mellema M, Bot A, Desobry S, Banon S. Influence of Calcium Salt Supplementation on Calcium Equilibrium in Skim Milk During pH Cycle. J Dairy Sci 2007; 90:2155-62. [PMID: 17430913 DOI: 10.3168/jds.2006-665] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Calcium is a mineral essential for humans, especially for bone constitution. Yet most of the worldwide population does not satisfy their Ca needs. Hence, Ca supplementation is of major importance, even in western countries where some specific populations at risk do not satisfy the recommended daily intake of Ca. More than 70% of dietary Ca comes from dairy products. Calcium supplementation of naturally Ca-rich sources such as skim milk is then of special interest. To our knowledge, few data are available concerning milk Ca (MC) supplementation of milk, particularly when followed by pH cycle. In this paper, MC supplementation is studied and compared with Ca chloride (CC) supplementation as a well-known source of Ca. The effect of Ca salt supplementation followed by pH cycle was studied in reconstituted skim milk. Calcium supplementation was carried out with CC and MC at 25 mmol of Ca/kg of skim milk. Ionized Ca concentration and turbidity variations were followed in situ by Ca ion selective electrode and turbidimetry using light reflection. From normalized data on ionized Ca concentration and turbidity vs. pH, it appeared that hysteresis areas were smaller for CC-supplemented milk, whereas unsupplemented milk and MC-supplemented milk behaved similarly. For these 3 dairy systems, pH cycles to pH 5.0 led to a larger hysteresis area than pH cycles to pH 5.5. The shrinkage of the hysteresis area could be interpreted as a reinforcement of casein micelles with Ca ions over the pH cycle.
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Affiliation(s)
- L S Canabady-Rochelle
- Nancy-University Laboratoire de Sciences et Gènie Alimentaires, Ecole Nationale Supérieure d'Agronomie et des Industries Alimentaires, 54 500 Vandoeuvre-Lés-Nancy, France.
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121
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Marchin S, Putaux JL, Pignon F, Léonil J. Effects of the environmental factors on the casein micelle structure studied by cryo transmission electron microscopy and small-angle x-ray scattering/ultrasmall-angle x-ray scattering. J Chem Phys 2007; 126:045101. [PMID: 17286511 DOI: 10.1063/1.2409933] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Casein micelles are colloidal protein-calcium-transport complexes whose structure has not been unequivocally elucidated. This study used small-angle x-ray scattering (SAXS) and ultrasmall angle x-ray scattering (USAXS) as well as cryo transmission electron microscopy (cryo-TEM) to provide fine structural details on their structure. Cryo-TEM observations of native casein micelles fractionated by differential centrifugation showed that colloidal calcium phosphate appeared as nanoclusters with a diameter of about 2.5 nm. They were uniformly distributed in a homogeneous tangled web of caseins and were primarily responsible for the intensity distribution in the SAXS profiles at the highest q vectors corresponding to the internal structure of the casein micelles. A specific demineralization of casein micelles by decreasing the pH from 6.7 to 5.2 resulted in a reduced granular aspect of the micelles observed by cryo-TEM and the existence of a characteristic point of inflection in SAXS profiles. This supports the hypothesis that the smaller substructures detected by SAXS are colloidal calcium phosphate nanoclusters rather than putative submicelles.
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122
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Augustin MA, Udabage P. Influence of Processing on Functionality of Milk and Dairy Proteins. ADVANCES IN FOOD AND NUTRITION RESEARCH 2007; 53:1-38. [PMID: 17900495 DOI: 10.1016/s1043-4526(07)53001-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The inherent physical functionality of dairy ingredients makes them useful in a range of food applications. These functionalities include their solubility, water binding, viscosity, gelation, heat stability, renneting, foaming, and emulsifying properties. The suitability of dairy ingredients for an application can be further tailored by altering the structure of the proteins using appropriate processes. The processes discussed include physical modification (heat treatment, acidification, addition of mineral slats, homogenization, and shear), enzymatic modification (renneting, hydrolysis, and transglutamination), and chemical modification (use of chemical agents and the Maillard reaction). Emerging food processes (high pressure and ultrasound) are also discussed. The challenges for using dairy ingredients for the delivery of nutrients and bioactive components, while maintaining physical functionality, are also highlighted. There is a need for continued research into the fundamental aspects of milk proteins and their responses to various stresses for further differentiation of milk products and for the delivery of ingredients with consistent quality for target applications.
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Affiliation(s)
- Mary Ann Augustin
- School of Chemistry, Monash University, Clayton, VIC 3800, Australia
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123
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124
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Diffusing wave spectroscopy of gelling food systems: The importance of the photon transport mean free path (l*) parameter. Food Hydrocoll 2006. [DOI: 10.1016/j.foodhyd.2005.02.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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125
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126
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Karlsson AO, Ipsen R, Schrader K, Ardö Y. Relationship Between Physical Properties of Casein Micelles and Rheology of Skim Milk Concentrate. J Dairy Sci 2005; 88:3784-97. [PMID: 16230684 DOI: 10.3168/jds.s0022-0302(05)73064-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The properties of casein micelles in milk concentrates are of interest for the use of ultrafiltered (UF) skim milk concentrates in dairy products, and for the general understanding of colloidal stability and behavior of the casein micelle. The rheological behavior of UF skim milk concentrate with a casein concentration of 19.5% (wt/wt) was investigated at different pH and NaCl concentrations by analyzing flow viscometry and small amplitude oscillatory shear measurements. Viscometric flow curves were fitted to the Carreau-Yasuda model with the aim of determining values for the viscosity at infinite high shear rates and thereby estimate the voluminosity of the casein micelles (nu(casein)) in the UF concentrate. The voluminosity of the casein micelles increased with addition of NaCl and decreased when pH was decreased from 6.5 to 5.5. At pH 5.2, nu(casein) increased because of acid-induced aggregation of the casein micelles. The changes in nu(casein) could be interpreted from transmission electron microscopy of freeze-fractured samples of the UF concentrate and partly from dynamic light scattering measurements. Altered interactions between casein micelles due to different pH and NaCl concentrations are proposed to occur due to collapse of the kappa-casein layer, changed ionic strength, and altered distance between casein micelles.
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Affiliation(s)
- A O Karlsson
- Dairy Technology, Department of Food Science, Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, Rolighedsvej 30, 1958 Fredriksberg C, Denmark.
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127
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Filipović D, Kasapović J, Pejić S, Nićiforović A, Pajović SB, Radojčić MB. Superoxide dismutase activity in various fractions of full bovine milk. ACTA ALIMENTARIA 2005. [DOI: 10.1556/aalim.34.2005.3.3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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128
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Alexander M, Dalgleish DG. Application of transmission diffusing wave spectroscopy to the study of gelation of milk by acidification and rennet. Colloids Surf B Biointerfaces 2005; 38:83-90. [PMID: 15465308 DOI: 10.1016/j.colsurfb.2004.08.012] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Accepted: 08/05/2004] [Indexed: 11/17/2022]
Abstract
Transmission diffusing wave spectroscopy has been used to study and compare three milk gelling systems (acid gelation of heated and unheated milks and rennet coagulation of unheated milk). In all cases, DWS was able to demonstrate the point of gelation as indicated by a rapid increase in particle size, as well as the small decreases in casein micelle radius attributed to the collapse or removal of the hairy kappa-casein layer. More importantly, the photon transport mean free path (l(*)) was measured. This parameter is unique to transmission DWS and can potentially give information about developing microstructures and the mechanical properties between different types of gels. The values of l(*) changed during the gelation processes, and these changes were manifested earlier than any change in particle aggregation or rheology of the systems. All three different gelling systems showed different changes in l(*) with time, showing the development of different interactions as the acidification or renneting reactions proceeded. Although a full analysis of the l(*) parameter and its changes cannot be made, it is concluded that they can provide important information on the pre-gelation states of aggregating systems.
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Affiliation(s)
- Marcela Alexander
- Department of Food Science, University of Guelph, Guelph, Ont., Canada N1G 2W1
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129
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130
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Cases E, Rampini C, Cayot P. Interfacial properties of acidified skim milk. J Colloid Interface Sci 2005; 282:133-41. [PMID: 15576091 DOI: 10.1016/j.jcis.2004.08.115] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Accepted: 08/13/2004] [Indexed: 10/26/2022]
Abstract
The purpose of this study is to investigate the tension properties and dilatational viscoelastic modulus of various skim milk proteins (whole milk, EDTA-treated milk, beta-casein, and beta-lactoglobulin) at an oil/water interface at 20 degrees C. Measurements are performed using a dynamic drop tensiometer for 15,000 s. The aqueous bulk phase is a skim milk simulated ultrafiltrate containing 11 x 10(-3) g L(-1) milk protein. At pH 6.7, beta-casein appears as the best to decrease the interfacial tension, whereas beta-lactoglobulin leads to the highest interfacial viscoelastic modulus value. Whole milk was almost as surface-active as individual beta-casein in terms of the final (steady-state) lowering of the interfacial tension, but the rate of tension lowering was smaller. EDTA treatment improved the rate of tension lowering of whole milk. The acidification of milk, from previous measurements, would lead to the enhancement of surface activity. At t=15,000 s, the order of effectiveness is pH 4.3 > pH 5.3 = pH 5.6 > pH 6.7 whole milk, suggesting that pH 4.3 whole milk is the best surface active. As compared to pH 6.7 whole milk, the use of pH 5.3 and pH 5.6 milk as surface active would result in the use of milk containing more free beta-casein born of pH-dissociated casein micelles.
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Affiliation(s)
- E Cases
- Laboratoire IMSA-ENSBANA, Campus Montmuzard 1, esplanade Erasme, Dijon, France.
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131
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Nelson BK, Lynch JM, Barbano DM. Impact of Milk Preacidification with CO2 on the Aging and Proteolysis of Cheddar Cheese. J Dairy Sci 2004; 87:3590-600. [PMID: 15483142 DOI: 10.3168/jds.s0022-0302(04)73497-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To determine the influence of milk preacidification with CO(2) on Cheddar cheese aging and proteolysis, cheese was manufactured from milk with and without added CO(2). The experiment was replicated 3 times. Carbon dioxide (approximately 1600 ppm) was added to the cold milk, resulting in a milk pH of 5.9 at 31 degrees C in the cheese vat. The starter and coagulant usage rates were equal for the control and CO(2) treatment cheeses. The calcium content of the CO(2) treatment cheese was lower, but no difference in moisture content was detected. The higher CO(2) content of the treatment cheeses (337 vs. 124 ppm) was maintained throughout 6 mo of aging. In spite of having almost one and a half times the salt-in-moisture, proteolysis as measured by pH 4.6 and 12% trichloroacetic acid soluble nitrogen expressed as percentages of total nitrogen, was higher in the CO(2) treatment cheeses throughout aging. The ratio of alpha(s)-casein (CN) to para-kappa-CN decreased faster in the CO(2) treatment cheeses than in the control cheeses, especially before refrigerated storage. No difference was detected in the ratio of beta-CN to para-kappa-CN between the control and CO(2) treatment cheeses. Intact alpha(s)- and beta-CN were found in the expressible serum (ES) from the CO(2) treatment cheese as well as alpha(s1)-I-CN, but they were not detected in the ES from the control cheese. No CN was detected in the ES from the curd before the salting of either the control or CO(2) treatment cheese. Higher proteolysis in the cheese made from milk preacidified with CO(2) may have been due to increased substrate availability in the water phase or increased chymosin activity or retention in the cheese.
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Affiliation(s)
- B K Nelson
- Northeast Dairy Foods Research Center, Department of Food Science, Cornell University, Ithaca, NY 14853, USA
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132
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Effect of pH at heating on the acid-induced aggregation of casein micelles in reconstituted skim milk. Lebensm Wiss Technol 2004. [DOI: 10.1016/j.lwt.2004.03.003] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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133
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134
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Uricanu VI, Duits MHG, Mellema J. Hierarchical networks of casein proteins: an elasticity study based on atomic force microscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:5079-90. [PMID: 15984271 DOI: 10.1021/la0363736] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
2D- and 3D-atomic force microscopy (AFM) experiments were performed on single casein micelles (CM) in native state, submerged in liquid, using a home-built AFM instrument. The micelles were immobilized via carbodiimide chemistry to a self-assembled monolayer supported on gold-coated slides. Off-line data analysis allowed the extraction of both surface topography and elastic properties. Relative Young moduli (E*) were derived from force-vs-indentation curves, using the Hertz theory. The obtained E* values were found to increase with CM diameter, following a straight line dependence. The data showed that temperature, via its influence on both the protein-protein interactions and the composition of the micelle, has a clear effect on the mechanical properties of the CMs: higher temperatures and lower serum casein concentrations result in stiffer micelles. For pH < or = 5.6, effecting calcium phosphate release from the micelles by decreasing the pH does not have a large effect on CM stiffness. On decrease of the pH below 5.0, particulate gels and multilayers were obtained. Their measured elasticity (expressed by an equivalent G'AFM) agrees remarkably well with the storage moduli as measured with a conventional rheometer. Compared to single micelles, gels from nonheated CM suspensions are about 3 orders of magnitude softer. The "softness" of these gels (measured under compression or shear) therefore must come from the microscopic and/or mesoscopic links rather than the micelles themselves.
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Affiliation(s)
- V I Uricanu
- Physics of Complex Fluids Group, University of Twente, Faculty of Science and Technology, J.M. Burgerscentrum for Fluid Mechanics, Institute of Mechanics, Processes and Control-Twente, Postbus 217, 7500 AE Enschede, Netherlands.
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135
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136
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137
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Zhang Z, Dalgleish DG, Goff HD. Effect of pH and ionic strength on competitive protein adsorption to air/water interfaces in aqueous foams made with mixed milk proteins. Colloids Surf B Biointerfaces 2004; 34:113-21. [PMID: 15261081 DOI: 10.1016/j.colsurfb.2003.11.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Revised: 11/12/2003] [Accepted: 11/26/2003] [Indexed: 10/26/2022]
Abstract
Quantitative analysis of competitive milk protein adsorption to air/water interfaces in aqueous foam was performed by capillary electrophoresis (CE). Foams were made by whipping protein solutions, in which skim milk powder (SMP) and whey protein isolate (WPI) were mixed at 0.5% protein in different proportions at different pH values and NaCl concentrations. Preferential adsorption of beta-casein into foam phases occurred under most solution conditions, if partial dissociation of the casein micelles had occurred. Preferential adsorption of beta-casein was not observed with added Ca2+, due to the re-association of casein micelles. Enrichment of caseins into the foam phase was more apparent than that of whey proteins. The foamability of SMP demonstrated a continuous improvement due to the gradually increasing dissociation of casein micelles when the concentration of NaCl increased from 0 to 0.8 M. The foamability of WPI increased when NaCl concentration rose from 0 to 0.1 M, and decreased with further increase in NaCl concentration. NaCl at low concentration (I < or = 0.4) did not show a significant effect on the competitive adsorption among milk proteins, indicating that electrostatic interactions do not play a key role in competitive adsorption. NaCl at higher concentration, e.g., 0.6 M, caused less whey protein to be adsorbed to the air/water interfaces. The whippability of WPI was highest at pH 4.5 and lowest at pH 3, and that of SMP was the opposite. The proportions of beta-lactoglobulin and alpha-lactalbumin in the foam phase were lower at acidic pH and higher at basic pH, compared with that at natural pH of WPI.
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Affiliation(s)
- Z Zhang
- Department of Food Science, University of Guelph, Guelph, Ont., Canada
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138
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Morin P, Jiménez-Flores R, Pouliot Y. Effect of Temperature and Pore Size on the Fractionation of Fresh and Reconstituted Buttermilk by Microfiltration. J Dairy Sci 2004; 87:267-73. [PMID: 14762069 DOI: 10.3168/jds.s0022-0302(04)73165-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The objective of this research was to evaluate the effect of temperature (7, 25, and 50 degrees C) and pore size (0.1, 0.8, and 1.4 micro m) on the separation of proteins and lipids (neutral lipids and phospholipids) during microfiltration (MF) of fresh or reconstituted buttermilk. Buttermilk was subjected to MF using a pilot-scale unit mounted with ceramic membranes. The MF runs were carried out in a uniform transmembrane pressure (UTP) mode. Changes in processing temperature had no significant impact on protein transmission, whereas increasing temperature reduced both lipid and phospholipid transmission. A maximum concentration factor (CF) for lipids was reached at 25 degrees C, as protein CF remained essentially unaffected by temperature. The use of the smaller pore size (0.1 microm) resulted in low lipid (10%) and protein (approximately 20%) transmission. Larger pore sizes (0.8 and 1.4 microm) resulted in higher levels of protein, lipid, and phospholipid transmission (>50%), but gave high permeation fluxes. Transmission of both proteins and lipids was markedly different when using fresh buttermilk as opposed to reconstituted buttermilk. This study showed that MF temperature, pore size, and buttermilk type influence fractionation but that MF alone cannot achieve optimal separation of lipids and proteins for the production of novel ingredients from buttermilk.
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Affiliation(s)
- P Morin
- Centre de recherche STELA, Université Laval, Ste-Foy, Québec, Canada
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139
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Ribeiro K, Rodrigues M, Sabadini E, Cunha R. Mechanical properties of acid sodium caseinate-κ-carrageenan gels: effect of co-solute addition. Food Hydrocoll 2004. [DOI: 10.1016/s0268-005x(03)00043-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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140
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Lucey J. Formation, Structural Properties and Rheology of Acid-coagulated Milk Gels. CHEESE: CHEMISTRY, PHYSICS AND MICROBIOLOGY 2004. [DOI: 10.1016/s1874-558x(04)80064-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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141
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Horne D, Banks J. Rennet-induced Coagulation of Milk. CHEESE: CHEMISTRY, PHYSICS AND MICROBIOLOGY 2004. [DOI: 10.1016/s1874-558x(04)80062-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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142
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Pastorino AJ, Hansen CL, McMahon DJ. Effect of pH on the Chemical Composition and Structure-Function Relationships of Cheddar Cheese. J Dairy Sci 2003; 86:2751-60. [PMID: 14507010 DOI: 10.3168/jds.s0022-0302(03)73871-5] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The objectives of this study were to determine the effect of pH on chemical, structural, and functional properties of Cheddar cheese, and to relate changes in structure to changes in cheese functionality. Cheddar cheese was obtained from a cheese-production facility and stored at 4 degrees C. Ten days after manufacture, the cheese was cut into blocks that were vacuum-packaged and stored for 4 d at 4 degrees C. Cheese blocks were then high-pressure injected one, three, or five times with a 20% (wt/wt) glucono-delta-lactone solution. Successive injections were performed 24 h apart. Cheese blocks were then analyzed after 40 d of storage at 4 degrees C. Acidulant injection decreased cheese pH from 5.3 in the uninjected cheese to 4.7 after five injections. Decreased pH increased the content of soluble calcium and slightly decreased the total calcium content of cheese. At the highest level, injection of acidulant promoted syneresis. Thus, after five injections, the moisture content of cheese decreased from 34 to 31%, which resulted in decreased cheese weight. Lowered cheese pH, 4.7 compared with 5.3, also resulted in contraction of the protein matrix. Acidulant injection decreased cheese hardness and cohesiveness, and the cheese became more crumbly. The initial rate of cheese flow increased when pH decreased from 5.3 to 5.0, but it decreased when cheese pH was further lowered to 4.7. The final extent of cheese flow also decreased at pH 4.7. In conclusion, lowering the pH of Cheddar cheese alters protein interactions, which then affects cheese functionality. At pH greater than 5.0, calcium solubilization decreases protein-to-protein interactions. In contrast, at pH lower than 5.0, the acid precipitation of proteins overcomes the opposing effect caused by increased calcium solubilization and decreased calcium content of cheese, and protein-to-protein interactions increase.
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Affiliation(s)
- A J Pastorino
- Western Dairy Center, Department of Nutrition and Food Sciences, Utah State University, Logan 84322, USA
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143
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144
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Laurent M, Boulenguer P. Stabilization mechanism of acid dairy drinks (ADD) induced by pectin. Food Hydrocoll 2003. [DOI: 10.1016/s0268-005x(03)00028-6] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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145
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Vasbinder AJ, Rollema HS, Bot A, de Kruif CG. Gelation mechanism of milk as influenced by temperature and pH; studied by the use of transglutaminase cross-linked casein micelles. J Dairy Sci 2003; 86:1556-63. [PMID: 12778566 DOI: 10.3168/jds.s0022-0302(03)73741-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Casein micelles in milk are colloidal particles consisting of four different caseins and calcium phosphate, each of which can be exchanged with the serum phase. The distribution of caseins and calcium between the serum and micellar phase is pH and temperature dependent. Furthermore, upon acidification casein micelles lose their colloidal stability and start to aggregate and gel. In this paper, we studied two methods of acid-induced gelation, i.e., 1) acidification of milk at temperatures of 20 to 50 degrees C and 2) decreasing the pH at 20 degrees C to just above the gelation pH and subsequently inducing gelation by increasing the temperature. These two routes are called T-pH and pH-T, respectively. The gelation kinetics and the properties of the final gels obtained are affected by the gelation route applied. The pH-T milks gel at higher pH and lower temperature and the gels formed are stronger and show less susceptibility to syneresis. By using intramicellar cross-linked casein micelles, in which release of serum caseins is prevented, we demonstrated that unheated milk serum caseins play a key role in gelation kinetics and characteristics of the final gels formed. This mechanism is presented in a model and is relevant for optimizing and controlling industrial processes in the dairy industry, such as pasteurization of acidified milk products.
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Affiliation(s)
- A J Vasbinder
- NIZO Food Research, P.O. Box 20, 6710 BA, Ede, The Netherlands
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146
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Nájera A, de Renobales M, Barron L. Effects of pH, temperature, CaCl2 and enzyme concentrations on the rennet-clotting properties of milk: a multifactorial study. Food Chem 2003. [DOI: 10.1016/s0308-8146(02)00270-4] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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147
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Horne DS. Casein micelles as hard spheres: limitations of the model in acidified gel formation. Colloids Surf A Physicochem Eng Asp 2003. [DOI: 10.1016/s0927-7757(02)00518-6] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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148
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Abstract
Various methods have been used to study the dissociation of milk micelles in attempts to determine their structure and the interactions that stabilize them. These include the addition of urea, cooling to alter hydrophobic bonding, the addition of EDTA to sequester calcium, and changes in pH to alter molecular charge. For this study, the mild chaotropic agent LiCl was added to human milk micelles, and measurements were made on the relative percentages of the six different phosphorylation levels of beta-casein (CN) at various LiCl concentrations for different lengths of time and at different temperatures. Added LiCl had little effect at 37 degrees C but caused maximal dissociation, mainly of the beta-CN species with higher phosphorylation levels, at 23 degrees C and 4 degrees C between 1 and 2 M concentration. Comparison was made with 2-M additions of NaCl, MgCl2, and KCl at 4 degrees C, with LiCl showing the only appreciable change. The results suggest that Li+ may displace Ca2+ in protein-Ca2+-protein or protein-colloidal calcium phos+ phate-protein salt bridges and that the nonphosphorylated form of human beta-CN may change its conformation and mode of interaction upon phosphorylation. Lithium chloride may be useful to study the dissociation of the different CN in bovine milk micelles.
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Affiliation(s)
- S M Sood
- Department of Biochemistry and Microbiology, School of Medicine, Loma Linda University, Loma Linda, CA 92350, USA.
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149
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Abstract
This article investigates the effect of sucrose addition on the formation of casein gels by acidification and/or renneting of pure micellar casein. Gelation kinetics and gel properties were followed by rheological methods, and microscopy and syneresis measurements were used to obtain a more complete characterization of the structures formed. Sucrose content has been identified as a key parameter for controlling the kinetics of aggregation and the strength of the final gels. Results have shown that the effect of sucrose on gelation can vary such that effects can be completely reversed depending on the gelation route used. During acid gelation, addition of up to 30% (wt/wt) sucrose causes gels to form more rapidly and at higher pH values, and to have higher viscoelastic moduli and a more homogeneous microstructure than those without sucrose. By contrast, gels formed by renneting in the presence of sucrose are weaker and have longer gelation times. It is proposed that sucrose reduces solvent quality and causes the collapse of the "hairy" kappa-casein brush on the surface of the casein micelles. This may explain why sucrose increases the possibility of gel formation during acidification and reduces the degree of kappa-casein hydrolysis during renneting.
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Affiliation(s)
- C Schorsch
- Unilever Research Colworth, Sharnbrook, Bedford MK44 1LQ UK
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150
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Harte F, Amonte M, Luedecke L, Swanson B, Barbosa-Canovas G. Yield Stress and Microstructure of Set Yogurt Made from High Hydrostatic Pressure-Treated Full Fat Milk. J Food Sci 2002. [DOI: 10.1111/j.1365-2621.2002.tb09535.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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