Effect of casein micelle composition and casein dephosphorylation on coagulation and syneresis

1986 ◽  
Vol 53 (3) ◽  
pp. 381-390 ◽  
Author(s):  
Martin J. Pearse ◽  
Peter M. Linklater ◽  
Robert J. Hall ◽  
Antony G. Mackinlay
Keyword(s):  
Adverse Effect ◽  
Casein Micelle ◽  
Coagulation Time ◽  
Rennet Coagulation ◽  
Phosphate Groups

SUMMARYThe effect of varying the casein composition of artificial micelle milk on rennet coagulation time and syneresis was examined in order to determine whether either of these processes is dependent on the concentration of particular casein components. It was found that the levels of κ-and β-caseins had a significant effect on coagulation, whereas syneresis was only affected by the level of β-casein. Partial dephosphorylation of preformed micelles or the incorporation of dephosphorylated or partly dephosphorylated β-casein into artificial micelle milk was found to have an adverse effect on both coagulation and syneresis. It was concluded that the phosphate groups of casein, particularly those of β-casein, are directly involved in the micelle-micelle interactions which occur during coagulation and syneresis.

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

2005 ◽  
Vol 72 (2) ◽  
pp. 226-233 ◽  
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.

Moving boundary electrophoresis of native and rennet-treated casein micelles

1976 ◽  
Vol 43 (1) ◽  
pp. 27-36 ◽  
Author(s):  
K. N. Pearce
Keyword(s):  
Density Gradient ◽  
Milk Sample ◽  
Moving Boundary ◽  
Electrokinetic Potential ◽  
Casein Micelle ◽  
Coagulation Time ◽  
Casein Micelles ◽  
Electrophoretic Mobilities ◽  
Rennet Coagulation ◽  
Micelle Surface

SummaryThe electrokinetic potential of bovine casein micelles was determined under a variety of conditions using moving boundary electrophoresis. The technique used allowed sharp stable boundaries to be formed without addition of density gradient-forming materials. Casein micelles are negatively charged and in any one milk sample all micelles had similar electrophoretic mobilities. The electrokinetic potential of micelles was markedly reduced by the action of rennet and to a lesser extent by a decrease in temperature from 30 to 6°C. Addition of sucrose to milk caused a small increase in the electrokinetic potential. Addition of anionic detergent to milk increased both the electrokinetic potential and the rennet coagulation time. Addition of cationic detergent caused a reduction in both these quantities, promoted syneresis of the rennet coagulum and caused coagulation in the absence of rennet if present in concentrations exceeding about 10 mM. Alteration of cation activities by addition of salts to milk caused complex changes, either increasing or decreasing the electrokinetic potential. The data obtained are most readily explained by a model for the casein micelle in which some, but not necessarily all, of the κ-casein is located at the micelle surface.

scholarly journals Changes of quality of rennets during storing

2012 ◽  
Vol 60 (6) ◽  
pp. 189-196
Author(s):  
Monika Kozelková ◽  
Miroslav Jůzl ◽  
Táňa Lužová ◽  
Květoslava Šustová ◽  
Aneta Bubeníčková
Keyword(s):  
Near Infrared ◽  
Color Change ◽  
Coagulation Time ◽  
Time Activity ◽  
Spectrophotometric Methods ◽  
Color Changes ◽  
Rennet Coagulation ◽  
Total Color Change ◽  
Instrumental Methods

This work deals about evaluation of qualitative parameters of rennets. During the six months storing of rennets were determined following qualitative parameters: pH, rennet coagulation time, activity (strange) of rennet and dose of rennet, and finally were used instrumental methods: Near infrared spectroscopy (NIR) for recognizing age of rennets and spectrophotometric methods of determining the color of rennets. The theory found in the references suggests, that the activity of rennet should decrease by an average of 1–2 % per month, but the results are showing, that are changing quality of rennets namely mostly activity (strange) of rennet, which was decreased by 33% per half year. In analysis of color of rennets weren’t observed major changes by the whole group. Some statistical differences were detected in the partial values L*a*b*, most advantageous were evaluation by rennet total color change during storage, which were higher than noticeable change in four samples. The least color changes (P > 0.05) were observed in microbial rennets, with no values observed (ΔEab < 2) that can be recognized even by the human eye when subjected to parallel comparison. It was found that the NIR analysis can be used to recognizing of rennets, which are different ages.

Composition and processability of bovine milk from herds with different calving patterns

2000 ◽  
Vol 25 ◽  
pp. 77-86 ◽  
Author(s):  
B. O’Brien
Keyword(s):  
Total Protein ◽  
Somatic Cell Count ◽  
Bovine Milk ◽  
Experimental Period ◽  
Early Lactation ◽  
Milk Supply ◽  
Coagulation Time ◽  
Rennet Coagulation ◽  
Product Manufacture ◽  
Continuous Product

AbstractThe chemical composition and processing characteristics of milks from spring and autumn calving herds were investigated to establish if an autumn/winter milk supply would overcome the variation in composition and quality which is characteristic of a seasonal milk supply. Three herds of 26 cows were established with mean calving dates of 22 February, 28 September and a 50:50 combination of both. The experimental period was from 5 August to 22 December. Bulk milks were collected separately from each of the three herds at one consecutive am and pm milking each week. Spring and autumn milks were also bulked in proportions of 70:30, 50:50 and 30:70, respectively. All milks were analysed for gross composition, protein fractions, renneting properties (rennet coagulation time [RCT], rate of curd aggregation [K20] and curd firmness [A60]), free fatty acids (FFA) and somatic cell count (SCC). Total protein and casein of spring milk were reduced (P<0.001) from 38.1 and 28.7 g/kg, respectively in the period 14 October-24 November to 33.8 and 25.9 g/kg in the period 25 November-22 December. This was accompanied by a deterioration (minimum P<0.01) in RCT from 21.7 to 33.3 min, in K20 from 8.2 to 15.2 min and in A60 from 43.8 to 30.8 mm. Autumn milk had higher fat (P<0.01) and lactose (P<0.001) concentrations, lower FFA levels (P<0.001), improved (P<0.001) RCT, K20 and A60 values compared to spring milk in the period 25 November-22 December. During this period, the 70:30 milk had improved RCT (P<0.01) and K20 (P<0.05) values and reduced (P<0.01) FFA levels compared to spring milk. It is concluded that the composition and processing characteristics of spring milk deteriorated after 275 days in milk. Changes in total protein and casein were closely associated with changes in renneting properties. Blending of autumn milk with spring milk improved the processing characteristics of the mix compared to those of spring milk. Thus, the introduction of early lactation autumn milk at the end of the spring lactation would maintain good milk processability and allow continuous product manufacture.

Association between the GHR, GHRHR and IGF1 gene polymorphisms and milk coagulation properties in Sarda sheep

2019 ◽  
Vol 86 (3) ◽  
pp. 331-336 ◽  
Author(s):  
Maria L. Dettori ◽  
Michele Pazzola ◽  
Emanuela Pira ◽  
Giorgia Stocco ◽  
Giuseppe M. Vacca
Keyword(s):  
Growth Hormone ◽  
Rate Constant ◽  
Hormone Receptor ◽  
Growth Hormone Receptor ◽  
Model Parameters ◽  
Coagulation Time ◽  
Rennet Coagulation ◽  
Milk Coagulation ◽  
Growth And Reproduction ◽  
Asymptotic Potential

AbstractWe investigated whether variation of the sheep Growth Hormone Receptor (GHR), Growth Hormone Releasing Hormone Receptor (GHRHR) and Insulin-Like Growth Factor 1 (IGF1) genes were associated with milk coagulation properties (MCP) in sheep. The GHR, GHRHR and IGF1 genes are part of the GH system, which is known to modulate metabolism, growth and reproduction as well as mammogenesis and galactopoiesis in dairy species. A total of 380 dairy Sarda sheep were genotyped for 36 SNPs mapping to these three genes. Traditional MCP were measured as rennet coagulation time (RCT), curd-firming time (k20) and curd firmness at 30 m (a30). Modeling of curd firming over time (CFt) was based on a 60 m lactodynamographic test, generating a total of 240 records of curd firmness (mm) for each milk sample. The model parameters obtained included: the rennet coagulation time as a result of modeling all data available (RCTeq, min); the asymptotic potential value of curd firmness (CFP, mm) at an infinite time; the CF instant rate constant (kCF, %/min); the syneresis instant rate constant (kSR, %/min); the maximum value of CF (CFmax, mm) and the time at achievement of CFmax (tmax, min). Statistical analysis revealed that variation of the GHR gene was significantly associated with RCT, kSR and CFP (P < 0.05). No other significant associations were detected. These findings may be useful for the dairy industry, as well as for selection programs.

Effect of milk concentration on the rennet coagulation time

1980 ◽  
Vol 47 (2) ◽  
pp. 231-235 ◽  
Author(s):  
Douglas G. Dalgleish
Keyword(s):  
Coagulation Time ◽  
Rennet Coagulation

SummaryMeasurements have been made of the coagulation times (CT) of concentrated and diluted milks when treated with chymosin. After dilution, milks showed a large increase in CT: conversely, concentrated milks showed a similar CT to unconcentrated milk. The results are discussed in terms of a mechanism which reduces to a form similar to that proposed by Holter (1932).

Composition of poorly and non-coagulating bovine milk and effect of calcium addition

2010 ◽  
Vol 77 (4) ◽  
pp. 398-403 ◽  
Author(s):  
Elin Hallén ◽  
Anne Lundén ◽  
Anna-Maria Tyrisevä ◽  
Maria Westerlind ◽  
Anders Andrén
Keyword(s):  
Bovine Milk ◽  
Protein Composition ◽  
Calcium Content ◽  
Casein Micelle ◽  
Independent Data ◽  
Coagulation Time ◽  
Data Set ◽  
Milk Samples ◽  
Micelle Size ◽  
Similar Association

Ninety-nine individual milk samples from 37 cows in lactation week 10–35, selected for producing well or poorly/non-coagulating milk, were compared regarding protein composition, total calcium content, casein micelle size, pH, and coagulating properties after addition of 0·05% CaCl2. The results showed that a low κ-casein concentration in milk was a risk factor for non-coagulation. CaCl2 addition improved coagulating properties (coagulation time, curd firmness) of nearly all samples and eliminated differences between poorly/non-coagulating and well-coagulating milk, particularly regarding curd firmness. A second, independent data set with 18 non-coagulating or well-coagulating milk samples were analysed for protein composition, where indications of a similar association with κ-casein was observed.

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