Physico-chemical properties of casein micelles reformed from urea-treated milk

1974 ◽  
Vol 41 (1) ◽  
pp. 45-53 ◽  
Author(s):  
T. C. A. McGann ◽  
P. F. Fox
Keyword(s):  
Binding Capacity ◽  
Chemical Properties ◽  
Heat Stability ◽  
Casein Micelles ◽  
Second Stage ◽  
Bulk Milk ◽  
Rennet Coagulation ◽  
Physico Chemical ◽  
Micelle Size ◽  
Ethanol Stability

SummaryMicelles reconstituted from urea-treated milk by exhaustive dialysis against bulk milk were similar to native micelles with respect to colloidal phosphate: casein ratio, ethanol stability, heat stability and susceptibility to first-stage rennin action. Reconstituted micelles were considerably smaller than native micelles as indicated by turbidity, sedimentation and viscosity, had shorter second-stage rennet coagulation times, were unstable to [Ca2+] > 20 mM and had reduced base-binding capacity. It is suggested that the induced Ca sensitivity is due to unfavourable alterations in the micellar κ-casein coat arising from the decrease in average micelle size and can be offset by increasing the κ-casein complement of the system or by increasing the degree of aggregation by slowly raising the [Ca2+] level.

Physico-chemical characteristics of casein micelles in dilute aqueous media

1979 ◽  
Vol 46 (2) ◽  
pp. 357-363 ◽  
Author(s):  
Patrick F. Fox ◽  
Bridget M. Nash
Keyword(s):  
Aqueous Media ◽  
Heat Stability ◽  
Coagulation Time ◽  
Casein Micelles ◽  
Second Stage ◽  
Rennet Coagulation ◽  
Physico Chemical ◽  
Micelle Size ◽  
Low Levels ◽  
Ph Range

SUMMARYThe heat stability and rennet coagulation time (second stage) of milk were reduced by brief dialysis against water. Destabilization appears to arise from a developed imbalance between Ca and phosphate plus citrate due to the very slow diffusion of Ca on dialysis. Average micelle size as indicated by permeation chromatography in porous glass CPG 10 was slightly reduced by dialysis for 24 h. Direct addition of low levels (10–100 mM) of NaCl to milk markedly reduced heat stability at pH > 7·0 (normal minimum) possibly due to dissociation of κ-casein, but increased rennet coagulation times; higher levels of NaCl decreased heat stability throughout the pH range 6·4–7·4.

Some physico-chemical properties of porcine milk

1975 ◽  
Vol 42 (1) ◽  
pp. 43-56 ◽  
Author(s):  
M. C. T. Hoynes ◽  
P. F. Fox
Keyword(s):  
Bovine Milk ◽  
Chemical Properties ◽  
Complete Removal ◽  
Heat Stability ◽  
Rennet Coagulation ◽  
Physico Chemical ◽  
Water Of Hydration ◽  
High Level ◽  
Ph Curve ◽  
Porcine Milk

SummaryThe principal results of an investigation of the major physico-chemical properties of porcine milk were:Heat stability: all individual porcine milks examined had poor heat stability and some coagulated in 2 min at 95°C; the Q10°C was high and variable and was 40 for some samples. Dialysis of porcine milk against bulk bovine milk did not influence its heat stability; removal of colloidal calcium phosphate (CCP) from porcine milk increased its heat stability 4-fold, but it was still very unstable. Unlike bovine milk, porcine milk did not exhibit a maximum-minimum in the heat stability-pH curve, but rather resembled bovine casein micelles suspended in milk dialysate. Addition of isolated bovine β-lactoglobulin to porcine milk did not influence its heat stability-pH curve.Rennet coagulation: under similar conditions, porcine milk coagulated about 4 times faster than bovine milk and the resultant curd was about twice as soft. Dialysis of porcine milk against a large excess of bulk bovine milk did not influence its rennet coagulability nor did removal of 50% of its CCP, but complete removal of the CCP rendered porcine milk non-coagulable by rennin. Porcine milk was readily coagulated by rennin down to 5°C; its second-stage coagulation was independent of temperature – a characteristic due mainly to its high level of CCP.Alcohol stability: porcine milk was coagulated by 66–68% (v/v) ethanol, as compared with 74% (v/v) for bovine milk.Calcium stability: porcine milk was stable to at least 300 mM-CaCl2 at both 2 and 37°C.Solvation: porcine milk contained significantly less water of hydration than bovine milk, 1·7g H2O/g casein compared with 2·0g H2O/g casein.

scholarly journals Reformation of casein particles from alkaline-disrupted casein micelles

2008 ◽  
Vol 75 (1) ◽  
pp. 44-47 ◽  
Author(s):  
Thom Huppertz ◽  
Betsy Vaia ◽  
Mary A Smiddy
Keyword(s):  
Zeta Potential ◽  
Serum Calcium ◽  
Heat Stability ◽  
Chloride Ions ◽  
Coagulation Time ◽  
Casein Micelles ◽  
Rennet Coagulation ◽  
Ethanol Stability

In this study, the properties of casein particles reformed from alkaline disrupted casein micelles were studied. For this purpose, micelles were disrupted completely by increasing milk pH to 10·0, and subsequently reformed by decreasing milk pH to 6·6. Reformed casein particles were smaller than native micelles and had a slightly lower zeta-potential. Levels of ionic and serum calcium, as well as rennet coagulation time did not differ between milk containing native micelles or reformed casein particles. Ethanol stability and heat stability, >pH 7·0, were lower for reformed casein particles than native micelles. Differences in heat stability, ethanol stability and zeta-potential can be explained in terms of the influence of increased concentrations of sodium and chloride ions in milk containing reformed casein particles. Hence, these results indicate that, if performed in a controlled manner, casein particles with properties closely similar to those of native micelles can be reformed from alkaline disrupted casein micelles.

Effect of acidification and neutralization of milk on some physico-chemical properties of casein micelles

1996 ◽  
Vol 6 (3) ◽  
pp. 257-272 ◽  
Author(s):  
J.A. Lucey ◽  
C. Gorry ◽  
B. O'Kennedy ◽  
M. Kalab ◽  
R. Tan-Kinita ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Casein Micelles ◽  
Physico Chemical

Evaluation of physico-chemical properties of tomato powder produced by an optimized freeze drying process

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Zeyu Wu ◽  
Haiyan Wang ◽  
Li Zhang ◽  
Zhaojun Xian ◽  
Honghong Li ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Freeze Drying ◽  
Binding Capacity ◽  
Chemical Properties ◽  
Soluble Solids ◽  
Drying Process ◽  
Total Acid ◽  
Physico Chemical ◽  
Freeze Dried ◽  
Tomato Powder

Abstract In this study, the physico-chemical properties of tomato powder produced by an optimized freeze drying process (FDP) were evaluated. With the lycopene content as the dependent variable, the optimum FDP conditions (i.e., thermal cracking time of 62 s, ascorbic acid addition amount [0.13%], and particle size [Dv90] of 163 μm) were obtained through response surface methodology (RSM). The results showed that the content of lycopene in the prepared tomato powder was higher than that in two commercial products. Aldehydes were the main components among 25 kinds of aromatic substances detected in tomato powder. The values of a * and a */b *, the hydration properties including water holding capacity (WHC) and oil binding capacity (OBC), and the content of total acid, ascorbic acid, and soluble solids were improved compared to commercial spray dried and freeze dried samples. All the above results suggested that FDP was an adequate procedure for the production of high-quality tomato powder.

Seasonal variation in the composition and processing characteristics of herd milk with varying proportions of milk from spring-calving and autumn-calving cows

2017 ◽  
Vol 84 (4) ◽  
pp. 444-452 ◽  
Author(s):  
Yingchen Lin ◽  
James A. O'Mahony ◽  
Alan L. Kelly ◽  
Timothy P. Guinee
Keyword(s):  
Milk Powder ◽  
Heat Stability ◽  
Casein Micelle ◽  
Total Calcium ◽  
Volume Proportion ◽  
Micelle Size ◽  
Total Milk ◽  
Herd Milk ◽  
Ethanol Stability ◽  
Total P

The study investigated the seasonal changes in the compositional, physicochemical and processing characteristics of milk from a mixed-herd of spring- and autumn-calving cows during the year 2014–2015. The volume proportion of autumn-calving milk (% of total milk) varied with season, from ~10–20 in Spring (March–May), 5–13 in Summer (June–August), 20–40 in Autumn (September–November) and 50–100 in Winter (December–February). While all characteristics varied somewhat from month to month, variation was inconsistent, showing no significant trend with progression of time (year). Consequently, season did not significantly affect many parameters including concentrations of total protein, casein, whey protein, NPN, total calcium, pH, rennet gelation properties or heat stability characteristics. However, season had a significant effect on the concentrations of total P and serum P, levels of αs1- and β-caseins as proportions of total casein, casein micelle size, zeta potential and ethanol stability. The absence of a significant effect of season for most compositional parameters, rennet gelation and heat-stability characteristics suggest that milk from a mixed-herd of spring- and autumn-calving cows is suitable for the manufacture of cheese and milk powder on a year-round basis, when the volume proportion of autumn milk, as a % of total, is similar to that of the current study.

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.

Comparative micelle structure: II. Structure and composition of casein micelles in ovine and caprine milk as compared with those in bovine milk

1974 ◽  
Vol 41 (2) ◽  
pp. 239-247 ◽  
Author(s):  
B. C. Richardson ◽  
L. K. Creamer ◽  
K. N. Pearce ◽  
R. E. Munford
Keyword(s):  
Bos Taurus ◽  
Bovine Milk ◽  
Chemical Properties ◽  
Ovis Aries ◽  
Capra Hircus ◽  
Casein Micelles ◽  
Mineral Contents ◽  
Caprine Milk ◽  
Micelle Size ◽  
Physical And Chemical

SummaryThe casein micelles of sheep (Ovis aries), goat (Capra hircus) and cow (Bos taurus) milks have been examined by electron microscopy. The ovine micelles were smaller than bovine micelles, most being below 80 nm diam. The caprine micelles were either large (c. 200 nm diam.), easily sedimented and electron-dense, or small (below 80 nm) and similar to the ovine micelles. Examination of the micelles using the freeze-etch technique showed, however, that they were all composed of subunits of similar dimensions (10–15 nm diam.).Electrophoresis of the caseins showed that there were differences between them, with the caprine casein containing a smaller proportion of its protein in the more mobile components. The mineral contents of the milks were also different, but these were apparently related to the different pH and casein contents of the milks. It is likely that the diiferences in micelle size distribution are determined by the physical and chemical properties of the casein components.

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