715. The relation between the chemical composition of milk and the stability of the caseinate complex: IV. Coagulation by heat

1958 ◽  
Vol 25 (2) ◽  
pp. 281-296 ◽  
Author(s):  
J. C. D. White ◽  
D. T. Davies
Keyword(s):  
Calcium Phosphate ◽  
Milk Protein ◽  
Heat Stability ◽  
Milk Composition ◽  
Ionized Calcium ◽  
Coagulation Time ◽  
Complex Iv ◽  
Stage Of Lactation ◽  
The Stability ◽  
The Relationship

1. The variation in the stability of milk protein to heat and the relationship between milk composition and heat stability were examined.2. The coagulation times of the majority of the milk samples decreased by a factor of about 3 with an increase in temperature of 10°C. over the range 130–150°C. Because of the general proportionality of the coagulation times at 130, 140 and 150°C., the coagulation time at 130°C. only were used as a measure of the stability of the samples to heat.3. The coagulation times of herd bulk milks ranged from 17·2 to 59·0 min. at 130°C., whereas the range for samples from individual cows was 0·6–86·2 min.4. Samples of colostrum were very unstable to heat, and milk from cows in late lactation tended to have the longest coagulation times, but otherwise there was little relation between the heat stability of milk and the stage of lactation of the cow.5. Although colostrum samples were comparatively rich in ionized calcium, their marked instability to heat appeared to be caused solely by their high content of lactalbumin plus lactoglobulin.6. The stability to heat of the calcium caseinate-calcium phosphate complex in all samples, other than colostrum, could not be closely related either to the concentration and composition of the complex or to the composition and salt-balance of the aqueous phase.7. When the calcium phosphate content of the caseinate complex was relatively low, the heat stability of the complex tended to be inversely related to the concentration of ionized calcium in the milk, but in general coagulation time was not related to the concentration of ionized calcium.

713. The relation between the chemical composition of milk and the stability of the caseinate complex: II. Coagulation by ethanol

1958 ◽  
Vol 25 (2) ◽  
pp. 256-266 ◽  
Author(s):  
D. T. Davies ◽  
J. C. D. White
Keyword(s):  
Chemical Composition ◽  
Milk Protein ◽  
Aqueous Ethanol ◽  
Subclinical Mastitis ◽  
Milk Composition ◽  
Ionized Calcium ◽  
Bulk Milk ◽  
The Stability ◽  
The Relationship ◽  
Ethanol Stability

1. The variation in the stability of milk protein to ethanol and the relationship between milk composition and ethanol stability were examined.2. Samples of herd bulk milk were very similar in stability to ethanol; the range of aqueous ethanol solutions required to coagulate the caseinate complex in an equal volume of milk was only 80–84% (v/v) ethanol. Samples from individual cows showed a wide variation in stability; coagulation was caused by ethanol solutions ranging in strength from 66 to 90% (v/v) ethanol.3. Colostrum was very unstable to ethanol but stability rapidly increased during the post-colostrum period to higher levels in mid-lactation. Late lactation and subclinical mastitis milk showed no definite bias towards stability or instability.4. The strength of ethanol required to coagulate the caseinate complex in an equal volume of milk was inversely related to the concentration of ionized calcium in the milk. The correlation coefficient was –0·76 (significant at 0·001 level) indicating that approximately 60% of the variation in stability was accounted for by the variation in the concentration of ionized calcium.5. The relationships between the concentrations of other milk constituents and stability to ethanol could be attributed to the interrelations of the concentrations of these constituents and the concentration of ionized calcium.

The stability of milk protein to heat: II. Effect on heat stability of ageing milk at different temperatures

1966 ◽  
Vol 33 (1) ◽  
pp. 83-91 ◽  
Author(s):  
D. T. Davies ◽  
J. C. D. White
Keyword(s):  
Milk Protein ◽  
Heat Stability ◽  
Subclinical Mastitis ◽  
Progressive Increase ◽  
Common Occurrence ◽  
Coagulation Time ◽  
Rate Of Increase ◽  
Different Temperatures ◽  
Significant Change ◽  
The Stability

SummaryThe effect on heat stability as measured by coagulation time, of storing separated milk at 20, 4 and −20 °C has been examined. Milk with a good coagulation (initial clots large) could be stored for at least 30 h at 20 °C, 1 week at 4 °C and 1 month at −20 °C with no significant change in coagulation time. With milks giving a poor coagulation (initial clots small), a common occurrence during storage at 20 °C was a marked progressive increase in coagulation time; the rate of increase was reduced by storage at 4 °C. The increase in coagulation time of these labile milks, which are usually obtained from cows with subclinical mastitis, may occur to the same extent in darkness as in light, may be enhanced by exposure to light or may occur only when the milk is exposed to light. From these results, together with others reported by Davies & White (1966) and White & Davies (1966) it is concluded that, in studying heat stability, milks giving a good coagulation should be regarded as in a different class from milks giving a poor coagulation.

Studies on the heat stability of milk protein: III. Effect of heat-induced acidity in milk

1975 ◽  
Vol 42 (1) ◽  
pp. 73-88 ◽  
Author(s):  
A. W. M. Sweetsur ◽  
J. C. D. White
Keyword(s):  
Special Reference ◽  
Milk Protein ◽  
Heat Stability ◽  
Total Serum ◽  
Ion Content ◽  
Coagulation Time ◽  
Initial Ph ◽  
Ph Decrease ◽  
The Relationship

SummaryAn examination was made of the effect of varying the protein, lactose and total serum ion content of milk on the rate of production of heat-induced acidity (as measured by pH decrease), on heat stability (as measured by coagulation time), on the relationship between coagulation time and initial pH of milk (as measured by coagulation time-pH curves) and on the interrelationship of these parameters. In addition, the effect on these parameters and their interrelationship of varying the composition and volume of the headspace atmosphere in contact with the milk was investigated. Explanations are proposed for the observed effects on heat stability of varying the composition of milk and the heating conditions, with special reference to the influence of heat-induced acidity.

The stability of milk protein to heat: I. Subjective measurement of heat stability of milk

1966 ◽  
Vol 33 (1) ◽  
pp. 67-81 ◽  
Author(s):  
D. T. Davies ◽  
J. C. D. White
Keyword(s):  
Milk Protein ◽  
Heating Temperature ◽  
Glass Tube ◽  
Heat Stability ◽  
Volume Effect ◽  
Sample Volume ◽  
Subjective Test ◽  
Coagulation Time ◽  
The Stability ◽  
Time Required

SummaryA subjective test for the determination of the stability of milk protein to heat is described. In the test, the time required for particles of coagulated protein to become visible throughout a 2·5-ml sample of separated milk maintained at 135°C in a glass tube rocking at 8 c/min is taken as a measure of stability. The precision of the test was such that single determinations were generally adequate.Coagulation time decreased by about 12% as rocking speed was increased over the range 4–12 c/min and increased by a factor of about 3 for a decrease in heating temperature of 10 degC over the range 140–105 °C; with some milks the Q10 °C value increased to 5–8 a temperature decreased. As sample volume was increased over the range 1–3 ml coagulation time increased, especially With milks whose coagulation was poor (initial clots small). This volume effect appeared to be a consequence of the accompanying decrease in the proportion of headspace oxygen to volume of milk.

Studies on the heat stability of milk protein: I. Interconversion of type A and type B milk heat-stability curves

1974 ◽  
Vol 41 (3) ◽  
pp. 349-358 ◽  
Author(s):  
A. W. M. Sweetsur ◽  
J. C. D. White
Keyword(s):  
Calcium Phosphate ◽  
Milk Protein ◽  
Heating Temperature ◽  
Type A ◽  
Heat Stability ◽  
Type B ◽  
Coagulation Time ◽  
Higher Temperature ◽  
Ph Curve ◽  
Β Lactoglobulin

SummaryCoagulation time–pH curves with a coagulation-time minimum around pH 6·8 (type A curve) could progressively become type B (no minimum) as the heating temperature was decreased from 150 to 130°C. The short coagulation time that most milks have when pH is around 6·8 was found to be the result of a ‘premature’ coagulation, probably caused by calcium phosphate deposition on the larger caseinate micelles. This is followed by a second coagulation, not visually detected, that coincides with the coagulation time that would be expected if no coagulation-time minimum existed on the coagulation time-pH curve. The coagulation time of milks giving type A and type B curves may therefore not be comparable.Forewarming milk for 30 min at 80°C can introduce or accentuate a coagulationtime minimum when the milk is subsequently heated at a higher temperature. The effects of adding β-lactoglobulin, copper and N-ethylmaleimide on the heat stability of milk were examined and explanations proposed for these effects.

The stability of milk protein to heat: III. Objective measurement of heat stability of milk

1966 ◽  
Vol 33 (1) ◽  
pp. 93-102 ◽  
Author(s):  
J. C. D. White ◽  
D. T. Davies
Keyword(s):  
Induction Period ◽  
Milk Protein ◽  
Heat Stability ◽  
Objective Measurement ◽  
Objective Test ◽  
Subjective Test ◽  
Coagulation Time ◽  
Rapid Coagulation ◽  
The Stability

SummaryAn objective test has been developed to help in assessing the value, as a method for determining the heat stability of milk, of the subjective test described by Davies & White (1966a). The objective test showed that coagulation time, as determined by the subjective test, is a reasonably accurate measure of the induction period that precedes the onset of initial rapid coagulation, but that coagulation proceeds in 2 different ways depending primarily on whether the coagulation of the milk is good (initial clots large) or poor (initial clots small). The latter finding confirms the view that in studying heat stability these 2 categories of milk should be examined separately.

Milk utilization and manipulation of composition in the future

1984 ◽  
Vol 9 ◽  
pp. 17-25 ◽  
Author(s):  
W. Banks ◽  
D. D. Muir
Keyword(s):  
Current Knowledge ◽  
Dairy Product ◽  
Milk Composition ◽  
Raw Material ◽  
Fine Tuning ◽  
Stage Of Lactation ◽  
Heat Treated ◽  
Restrictive Legislation ◽  
Milk Solids ◽  
The Relationship

SUMMARYMilk composition varies greatly throughout the year, due largely to the effects of the diet of the cow and the stage of lactation. Whilst such variations go unremarked with bottled and cartoned milk, they are of major importance to manufacturers who use milk as a raw material. The most obvious example is when the yield of a dairy product is affected, e.g. in Scotland, the volume of milk required to produce 1 kg butter varies between 21.1 and 23.3 1 at different times of the year.In addition, however, some of the more subtle changes in milk composition either affect product quality, e.g. the ease with which butter may be spread, or cause processing difficulties, e.g. instability during heating processes. This paper reviews some of our current knowledge on the relationship between milk composition and the properties of some dairy products — butter, whipping cream, Cheddar cheese, ultra-heat treated milk and full-cream evaporated milk. The aim is to identify those milk components that affect each product or process and then enquire how milk composition may be altered to effect improvements — whether at the farm by dietary manipulation or at the creamery by technological adjustment.It is believed that all the evidence indicates that, despite difficulties due to restrictive legislation, the answer must lie at the creamery. The farmer should concentrate on producing desirable milk solids at the lowest possible cost and leave the technologist to do the fine tuning that leads to improved products.

Effect of urea on the heat coagulation of the caseinate complex in skim-milk

1977 ◽  
Vol 44 (2) ◽  
pp. 249-257 ◽  
Author(s):  
D. D. Muir ◽  
A. W. M. Sweetsur
Keyword(s):  
Activation Energy ◽  
Skim Milk ◽  
Heat Stability ◽  
Coagulation Time ◽  
Temperature Range ◽  
The Stability

SummaryAdditions of urea progressively increased the heat stability of milk outside of its coagulation time (CT)–pH minimum. In the region of the CT–pH minimum larger amounts of urea were required before an increase in heat stability occurred. The effect of urea was observed over the temperature range 125–140 °Cfornaturalmilk, milk which had been dialysed against synthetic sera, and milk to which a sulphydrylblocking agent had been added. Urea additions did not affect the activation energy of the heat coagulation reaction or the stability of milk to rennet or ethanol.

Bovine milk composition parameters affecting the ethanol stability

2004 ◽  
Vol 71 (2) ◽  
pp. 201-206 ◽  
Author(s):  
Mónica S Chavez ◽  
Livia M Negri ◽  
Miguel A Taverna ◽  
Alejandra Cuatrín
Keyword(s):  
Freezing Point ◽  
Bovine Milk ◽  
Heat Stability ◽  
Raw Milk ◽  
Milk Composition ◽  
Coagulation Time ◽  
Measured Variable ◽  
Ionic Calcium ◽  
Natural Milk ◽  
Ethanol Stability

The objective of the present work was to identify the compositional parameters of raw milk that affected ethanol stability at natural pH when natural milk conditions were not modified. Heat stability, measured as coagulation time (CT), was included in the analysis to verify relation to alcohol test. Statistical models were proposed for alcohol and heat (CT) stabilities. Milk samples of good hygienic quality from dairy farms were classified in two groups according to their alcohol stability. Unstable samples to ethanol (72%, v/v) presented lower values of pH, somatic cells count, casein and non-fat-solids relative to ethanol stable samples (ethanol at 78%, v/v or more); whereas freezing point, chloride, sodium and potassium concentrations were higher in the unstable group. Logistic regression and multiple regression were applied to modelling alcohol and heat stability behaviour respectively. Chloride, potassium, ionic calcium and somatic cell count were included in the alcohol regression model, whereas calcium, phosphorous, urea, pH and ionic calcium were part of CT model. Ionic calcium was the only measured variable that contributed to both models; however coagulation time was noted to be more sensitive to ionic calcium than alcohol. The relation between ionic strength and casein was found to contribute to the alcohol model but not to the CT model. However, the interaction calcium plus magnesium plus phosphorous and casein contributed only to CT model.

scholarly journals The trend of cowmilk yield, its compostion and the body condition during the lactation

2009 ◽  
pp. 69-73
Author(s):  
Edit Mikó Józsefné Jónás ◽  
Imre Mucsi ◽  
István Komlósi
Keyword(s):  
Dairy Cows ◽  
Body Condition ◽  
Milk Fat ◽  
Milk Protein ◽  
Milk Composition ◽  
Fat Content ◽  
The Body ◽  
Significant Difference ◽  
The Relationship ◽  
Body Condition Scores

The authors examined the data of 2767 trial milkings andthe months Body Condition Scores of 479 Holstein dairy cows. The condition loss was significant between the 30-60th days. The improvement of BCS begins only after the 120th day. The change in the milk protein and milk fat content were close after the condition changing. In each period of the lactation the closeness of the relationship among the condition, the milk quantity and the milk composition were different. In the aspect of the milk quantity the most significant difference was between the 2.5 and 4 BCS cows (6.68 kg) in the last period of the lactation.

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