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Tieu S, Harte F. Effect of mild thermal and pH changes on the sol-gel transition in skim milk. J Dairy Sci 2022; 105:7926-7939. [PMID: 35965122 DOI: 10.3168/jds.2021-21299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 03/13/2022] [Indexed: 11/19/2022]
Abstract
The present work aimed to improve acid and rennet milk gelation properties with mild thermal and pH changes to skim milk, with emphasis on heating temperatures below the denaturation temperature of whey proteins. We hypothesized the heat-induced, pH-dependent micellar changes, namely the shifts in casein and calcium equilibria between the micellar (or colloidal) and serum phases, result in firmer acid and rennet milk gels and reduced gelation time. Homogenized, pasteurized skim milk was adjusted to pH values in the range of 6.4 to 7.3, heated at temperatures in the range of 50 to 80°C, cooled to refrigeration temperature, and restored to native pH (pH 6.7). Then, acid and rennet gels were made by the addition of glucono-δ-lactone and chymosin, respectively. We monitored the storage modulus (G', Pa) during gel formation with small-amplitude oscillatory shear and the gelation time and maximum G' (G'max, Pa) of acid and rennet gels, were measured at 3 and 2 h, respectively. When skim milk was heated at 50°C for 15 min, there was a 58 and 163% increase in the G'max of acid and rennet gels, respectively, as the pH at heating was raised from pH 6.7 to 7.3. Increases in gel strength were greater for skim milk heated at 60°C for 15 min. There was a positive correlation between G'max of acid gels and the heat-induced casein protein exchanges between the micellar and serum phases on heating milk at pH in the range from 6.4 to 7.3 (r = 0.78). We also found positive correlations between the variation in G'max of rennet gels with the heat-induced, pH-dependent migration of casein (r = 0.83) and calcium (r = 0.80) from the micelle into the serum phase, as determined by PAGE and atomic emission spectroscopy. Under these mild heating temperatures (50 and 60°C), rennet coagulation time was significantly reduced from 45 ± 5 to 27 ± 3 min when the pH at heating was raised from pH 6.7 to 7.3. The ability to enhance milk gelation properties with a scalable pretreatment allows for the expression of novel functionality of casein.
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Affiliation(s)
- Stiphany Tieu
- Department of Food Science, The Pennsylvania State University, University Park 16802
| | - Federico Harte
- Department of Food Science, The Pennsylvania State University, University Park 16802.
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Maloney A, Herskowitz LJ, Koch SJ. Effects of surface passivation on gliding motility assays. PLoS One 2011; 6:e19522. [PMID: 21674032 PMCID: PMC3108588 DOI: 10.1371/journal.pone.0019522] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Accepted: 04/06/2011] [Indexed: 11/18/2022] Open
Abstract
In this study, we report differences in the observed gliding speed of
microtubules dependent on the choice of bovine casein used as a surface
passivator. We observed differences in both speed and support of microtubules in
each of the assays. Whole casein, comprised of αs1,
αs2, β, and κ casein, supported motility and averaged
speeds of 966±7 nm/s. Alpha casein can be purchased as a combination of
αs1 and αs2 and supported gliding motility and
average speeds of 949±4 nm/s. Beta casein did not support motility very
well and averaged speeds of 870±30 nm/s. Kappa casein supported motility
very poorly and we were unable to obtain an average speed. Finally, we observed
that mixing alpha, beta, and kappa casein with the proportions found in bovine
whole casein supported motility and averaged speeds of 966±6 nm/s.
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Affiliation(s)
- Andy Maloney
- Department of Physics and Astronomy and Center for High Technology Materials, University of New Mexico, Albuquerque, New Mexico, United States of America.
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Simple methods for the purification of crude κ-casein and β-casein by treatment with calcium phosphate gel. J DAIRY RES 2009. [DOI: 10.1017/s0022029900012851] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SummaryBatch methods applicable on a large scale are described for the purification of crude κ- and βκ-Casein, dissolved in urea-containing buffer, was freed from αs- and β-caseins by treatment with calcium phosphate gel and recovered in about 60% yield. β-Casein was freed from most impurities by adsorption on to calcium phosphate gel at pH 7·8 in the presence of urea and elution with 6 M-urea–N-NH4OH at 4°C. The recovery was about 50%.
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The specificity for κ-casein as the stabilizer of αs-casein and β-casein. I. Replacement of κ-casein by other proteins. J DAIRY RES 2009. [DOI: 10.1017/s0022029900013637] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
SummaryThe specificity of the interaction betweenκ-casein,αs-casein andβ-casein which forms the basis of micelle stabilization was studied by investigating the extent to whichκ-casein could be replaced by other proteins. Of those tested, only gelatin replacedκ-casein and even it was only 2·5% (w/v) as effective and required a long pre-incubation period. The micelles formed by each ofκ-casein and gelatin withαs-casein and Ca2+were of a similar size to the casein—Ca complexes which compose natural micelles. Gelatin also formed complexes withαs- and withβ-casein at 30°C in the absence of CaCl2. Evidence was obtained that the interactions between gelatin and the caseins had a much stronger ionic component than had those betweenκ-casein and the other caseins. It was concluded that the interactions betweenκ-casein andαs- andβ-caseins which lead to micelle formation are highly specific and probably involve definite sites in each molecule.
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Affiliation(s)
- Gordon A Morris
- Division of Food Sciences, School of BioSciences, University of Nottingham, Sutton Bonington, LE12 5RD, UK.
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Abstract
A new method was developed for obtaining pure beta-CN. Calcium caseinate (3%) was reconstituted, renneted to form a gel, cooled (4 degrees C) to allow beta-CN dissociation from the caseinate gel, and centrifuged. The supernatant was warmed to 30 degrees C, precipitating pure beta-CN from solution. Large quantities of beta-CN were recovered by scaling-up this procedure, but these beta-CN preparations were less pure than the beta-CN that was prepared on a smaller scale. Chromatography (FPLC) and urea-PAGE showed beta-CN to be the main component in the precipitate. Chymosin, used to form the caseinate gel, did not extensively hydrolyze beta-CN under the conditions of these experiments. Calcium concentration, cooling time, and caseinate concentration influenced the recovery of beta-CN. Maximum recovery of beta-CN, under the experimental conditions used, occurred at 10 mM calcium, 48 h of cooling, and 3% caseinate concentration.
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Affiliation(s)
- L S Ward
- Department of Nutrition and Food Science, University of Minnesota, St. Paul 55108, USA
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Imafidon GI, Ng-Kwai-Hang K. Effect of genetic polymorphisms on the susceptibility of β-casein to calcium precipitation and stabilizing effects of κ-casein. Int Dairy J 1992. [DOI: 10.1016/0958-6946(92)90032-h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Hirose M, Kato T, Omori K, Takeuchi M, Yoshikawa M, Sasaki R, Chiba H. Purification and characterization of four components of rat caseins. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 671:139-45. [PMID: 7326261 DOI: 10.1016/0005-2795(81)90127-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Rat casein components (C1-, C3A-, C3B- and C4-casein) were extensively purified from rat milk, and the properties of these proteins were compared with those of other caseins including rat C2-casein. C1-casein was precipitated by a low concentration of CaCl2 (1.5 mM). Both C3A- and C3B-casein were less sensitive to Ca2+ than were C1- and C2-casein, and the presence of 20 mM CaCl2 was required at 37 degrees C for their precipitation. C4-casein was absolutely insensitive to Ca2+. This protein exhibited the ability to stabilize all of the other rat casein components against Ca2+-dependent precipitation. In addition, C4-casein contained sialic acid, galactose and N-acetylgalactosamine. Therefore, C4-casein appears to be a bovine kappa-casein-like protein.
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Hirose M, Kato T, Omori K, Maki M, Yoshikawa M, Sasaki R, Chiba H. Purification and properties of a major casein component of rat milk. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 667:309-20. [PMID: 7194117 DOI: 10.1016/0005-2795(81)90197-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
A casein component (C2-casein) was purified by ion-exchange and gel filtration chromatography from rat milk, and the properties of this protein were examined. The molecular weight of C2-casein, as determined by Sepharose 4B gel filtration in 6 M guanidine hydrochloride, was 34 000 +/- 1000. The average hydrophobicity calculated from the amino acid composition showed that C2-casein is a rather hydrophilic protein. The alpha-helix content obtained from optical rotatory dispersion experiments was about 12%. In ultracentrifugation analyses, monomer and polymer peaks of C2-casein were both seen, and the monomer-to-polymer ratio was not affected by changing temperature conditions. C2-casein was precipitated by the presence of 2.5 mM CaCl2, and the precipitability was greatly decreased by the dephosphorylation of the protein. C2-casein was stabilized from Ca2+-dependent precipitation by the addition of another rat casein component (C3-casein) or of bovine kappa-casein.
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Slattery CW. A phosphate-induced sub-micelle-micelle equilibrium in reconstituted casein micelle systems. J DAIRY RES 1979; 46:253-8. [PMID: 469052 DOI: 10.1017/s0022029900017131] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
SUMMARYIn reconstituted casein systems, complete sub-micelles were previously observed only under extreme conditions of ionic strength, namely a NaCl concentration of 2 M or greater. However, studies with the analytical ultracentrifuge on phosphate-containing casein systems revealed that under certain conditions, a stable sub-micelle-micelle equilibrium was established. Conditions which were standard throughout were 7.5 mg/ml protein, 0.04 M-NaCl, pH 6.6 and 37 °C. The concentrations of added CaCl2 (Ca2+) and inorganic phosphate (P1) were variable. With no P1 present, Ca-sensitive caseins precipitated or formed micelles when k-casein was present, between 6 and 7 mM-Ca2+. With 10–20 mM-P1 precipitation or micelle formation began at about 4 mM-Ca2+ and was complete at about 5 mM-Ca2+. Over this interval, during micelle formation, a sub-micelle peak with s20, w of about 13 S was observed in equilibrium with the broad micelle peak. In a system containing a 2:2:1 weight ratio of ±sI-:²-:k-casein, this sub-micelle was isolated at 4 mM-Ca2+ and 2.5 mM-P1. The mol. wt was 760000 and it thus contained approximately 33 monomer caseins. The reconstituted micelle system formed in the absence of P1 was quite temperature sensitive, forming at 37 °C but disappearing upon cooling. In the presence of P1 the micelles formed at 37 °C but were stable to cooling as are natural micelles. Evidently, a combination of hydrophobic and electrostatic interactions are involved in natural micelle formation, probably with the production of salt bridges of Ca and phosphate ions between sub-micelles.
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Abstract
Both alpha-S1- and kappa-caseins were incubated at 37 C in the presence of bovine plasmin (.28 mg/ml) prepared from fresh blood plasma. The electrophoretic pattern of kappa-casein A was unchanged following 60-min incubation with plasmin. However, the electrophoretic band corresponding to alpha-S1-casein B gradually disappeared during the initial 30-min incubation with plasmin. Proteolysis was accompanied by the formation of one polypeptide band with electrophoretic mobility slightly slower than alpha-S1-casein B and several bands with faster electrophoretic mobilities. Two of the faster electrophoretic bands contained phosphorus. Estimates of molecular weights were 20,500, 12,300, and 10,300 daltons for three of these early degradation products of alpha-S1-casein B by plasmin.
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Eigel W, Randolph H. Comparison of Calcium Sensitivities of αs1-B, β-A2, and γ-A2 Caseins and Their Stabilization by K-Casein A. J Dairy Sci 1976. [DOI: 10.3168/jds.s0022-0302(76)84185-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Hill RJ, Wake RG. Amphiphile nature of k-casein as the basis for its micelle stabilizing property. Nature 1969; 221:635-9. [PMID: 5818473 DOI: 10.1038/221635a0] [Citation(s) in RCA: 75] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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THOMPSON MP, TARASSUK NP, JENNESS R, LILLEVIK HA, ASHWORTH US, ROSE D. Nomenclature of the Proteins of Cow's Milk—Second Revision. J Dairy Sci 1965; 48:159-69. [PMID: 14277415 DOI: 10.3168/jds.s0022-0302(65)88188-7] [Citation(s) in RCA: 64] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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