Factors affecting the action of rennin in heated milk

1972 ◽  
Vol 39 (3) ◽  
pp. 413-419 ◽  
Author(s):  
G. A. Wilson ◽  
J. V. Wheelock
Keyword(s):  
Complex Formation ◽  
Heat Stability ◽  
Primary Phase ◽  
Effect Of Temperature ◽  
Heat Denaturation ◽  
Clotting Time ◽  
Factors Affecting ◽  
Heated Milk ◽  
Whole Milk ◽  
Β Lactoglobulin

SummaryThe effect of temperature and time of heating whole milk on the renninclotting time, the primary phase of rennin action and the protein (mainly β-lactoglobulin) soluble in 2% trichloroacetic acid (TCA), have been studied. Considerable changes in these parameters occurred above 60°C. The primary phase was inhibited (the degree of inhibition being both temperature and time-dependent), the clotting time was increased, and the protein soluble in 2% TCA decreased considerably.It is suggested that the inhibition of the primary phase was due to complex formation between κ-casein and β-lactoglobulin, the increase in clotting time to a combination of complex formation and a change in the distribution of Ca, and the decrease in β-lactoglobulin to both its interaction with κ-casein and its heat denaturation. The relevance of such changes to the heat stability of milk is discussed.

The Role of β-lactoglobulin in the primary phase of rennin action on heated casein micelles and heated milk

1974 ◽  
Vol 41 (3) ◽  
pp. 367-372 ◽  
Author(s):  
J. V. Wheelock ◽  
A. Kirk
Keyword(s):  
Heat Treatment ◽  
Complex Formation ◽  
Skim Milk ◽  
Primary Phase ◽  
Casein Micelles ◽  
Heated Milk ◽  
Β Lactoglobulin

SummaryIt has been shown that the inhibition caused by heat treatment, of the primary phase of rennin action on casein micelles, is dependent on the presence of β-lactoglobulin. The degree of inhibition increased with increasing amounts of added β-lactoglobulin for both heated casein micelles and heated skim-milk to a constant value. The results are fully consistent with the hypothesis that the inhibition is caused by complex formation between β-lactoglobulin and κ-casein when milk is heated.

The effect of reduction and alkylation on the primary phase of rennin action on unheated and heated milk

1974 ◽  
Vol 41 (1) ◽  
pp. 37-44 ◽  
Author(s):  
G. A. Wilson ◽  
J. V. Wheelock ◽  
A. Kirk
Keyword(s):  
Alkylating Agents ◽  
Primary Phase ◽  
Cross Link ◽  
Ethylene Dibromide ◽  
Disulphide Bonds ◽  
Heated Milk ◽  
Whole Milk ◽  
Cross Links ◽  
Β Lactoglobulin ◽  
Normal Inhibition

SummaryThe effects of cystine-reducing and sulphydryl-alkylating agents on the extent of the primary phase of rennin action on unheated and heated milk samples were studied. Alkylating agents alone had a negligible effect, but heated samples, reduced with tri-n-butyl phosphine prior to alkylation with a mono-functional agent (sodium iodoacetate) did not show the usual inhibition of the primary phase. Heated samples, reduced and alkylated with a bi-functional agent (ethylene dibromide) which can re-cross-link the broken disulphide bonds, however, did give the normal inhibition. These results suggest that effects on the primary phase due to heat treatment of milk are determined to a large extent by rearrangement of the disulphide cross-links, and if these are permanently broken, heat appears to have little effect.The results differ in some important respects from those obtained on the complex formed between isolated β-lactoglobulin and isolated κ-casein, and therefore throw doubt on the generally held view that there is a similar type of interaction in whole milk.

Effects of β-lactoglobulin and κ-casein genetic variants and concentrations on syneresis of gels from renneted heated milk

1989 ◽  
Vol 56 (2) ◽  
pp. 297-301 ◽  
Author(s):  
Douglas M. McLean ◽  
Johan Schaar
Keyword(s):  
Genetic Polymorphism ◽  
Complex Formation ◽  
Genetic Variants ◽  
Milk Protein ◽  
Major Influence ◽  
Essential Requirement ◽  
Heated Milk ◽  
Cheese Curd ◽  
Processing Properties ◽  
Β Lactoglobulin

Milk protein genetic polymorphism has a major influence on the composition of milk, and on its processing properties, including yield of cheese (see Schaaret al.1985; McLeanet al.1984, 1987; McLean, 1987). However, there appears to be little information on the effects of milk protein genetic variants on syneresis of cheese curd. The effect of casein composition on syneresis was studied by Pearseet al.(1986), who found that syneresis was affected only by the level of β-casein. Syneresis is an essential requirement in cheese making from renneted or acidified milk, but is undesirable during the storage of products such as yogurt. Milk for yogurt manufacture is preheated to minimize syneresis and to give maximal firmness of the yogurt coagulum (Tamime & Deeth, 1980). Pearseet al.(1985) showed that the reduction of one-third in the extent of syneresis caused by heating artificial micelle milk (AMM) containing βlactoglobulin (β-lg) in natural concentrations was due to sulphydryl-mediated complex formation between β-lg and micellar κ-casein which appeared to interfere with the micelle–micelle interactions responsible for syneresis. The results presented here were part of a study which investigated the effects of κcasein and κ-lg genetic variants and concentrations on syneresis of curd formed from renneted heated AMM.

The effect of concentration on the heat stability of skim-milk

1978 ◽  
Vol 45 (1) ◽  
pp. 37-45 ◽  
Author(s):  
D. D. Muir ◽  
A. W. M. Sweetsur
Keyword(s):  
Opposite Effect ◽  
Skim Milk ◽  
Heat Stability ◽  
Progressive Change ◽  
Ph Profile ◽  
Total N ◽  
Heated Milk ◽  
Depletion Curve ◽  
Concentrated Milk ◽  
Β Lactoglobulin

SummaryA progressive change takes place in the heat stability of skim-milk during concentration. At the maximum in the coagulation time (CT)–pH profile of milk concentrated to over 20% of total solids (TS) the total N depletion curve changed from single- to 2-stage and CT became insensitive to the addition of urea. Furthermore, addition of β-lactoglobulin to skim-milk concentrates destabilized the heated milk whilst the opposite effect was observed in the presence of sulphydryl-group blocking agents. As a result of these observations, it has been suggested that the mechanism of coagulation in concentrated milk is similar to that which occurs within the minimum of the CT–pH profile of skim-milk at normal levels of TS.

Influence of sulphydryl group interactions on the heat stability of homogenized concentrated milk

1983 ◽  
Vol 50 (3) ◽  
pp. 301-308 ◽  
Author(s):  
A. W. Maurice Sweetsur ◽  
D. Donald Muir
Keyword(s):  
Complex Formation ◽  
Heat Stability ◽  
Group Interactions ◽  
Sulphydryl Group ◽  
Oxidizing Agents ◽  
Concentrated Milk ◽  
Β Lactoglobulin

SUMMABYThe heat stability of homogenized concentrated milk was found to be more susceptible than that of unhomogenized concentrated milk to changes in the ratio of β-lactoglobulin to κ-casein which were deliberately designed to alter the extent of disulphide-linked complex formation during heating. When sulphydryl group interactions were prevented by the addition to the milk before homogenization of blocking or oxidizing agents, homogenization did not change the heat stability of subsequently concentrated milk.

The primary phase of rennin action in heat-sterilized milk

1970 ◽  
Vol 37 (3) ◽  
pp. 389-396 ◽  
Author(s):  
E. J. Hindle ◽  
J. V. Wheelock
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Trichloroacetic Acid ◽  
Primary Phase ◽  
Carbohydrate Moiety ◽  
Whole Milk ◽  
Temperature Heat ◽  
Sterilization Process ◽  
Sterilized Milk ◽  
Β Lactoglobulin

SummaryThe action of rennin in milk subjected to the ultra-high-temperature heat sterilization process has been studied. The primary phase of rennin action, as determined by the release of peptides soluble in trichloroacetic acid, was partially inhibited as a result of the heat treatment. This was largely due to a reduction in the release of non-carbohydrate-containing peptides from κ-casein. It is suggested that when whole milk is heated the formation of a complex between β-lactoglobulin and κ-casein proceeds more readily with the species of κ-casein which lacks carbohydrate. Evidence is presented which shows that there may be more than one type of carbohydrate moiety attached to κ-casein.

Effect of Temperature, Velocity Gradient and I.V. Heparin on in Vitro Blood Coagulation and Platelet Aggregation

1967 ◽  
Vol 17 (01/02) ◽  
pp. 112-119 ◽  
Author(s):  
L Dintenfass ◽  
M. C Rozenberg
Keyword(s):  
Blood Coagulation ◽  
Velocity Gradient ◽  
Elevated Temperatures ◽  
Morphological Changes ◽  
Effect Of Temperature ◽  
Clotting Time ◽  
Progressive Change ◽  
Aggregation Of Platelets ◽  
Microscopic Techniques

SummaryA study of blood coagulation was carried out by observing changes in the blood viscosity of blood coagulating in the cone-in-cone viscometer. The clots were investigated by microscopic techniques.Immediately after blood is obtained by venepuncture, viscosity of blood remains constant for a certain “latent” period. The duration of this period depends not only on the intrinsic properties of the blood sample, but also on temperature and rate of shear used during blood storage. An increase of temperature decreases the clotting time ; also, an increase in the rate of shear decreases the clotting time.It is confirmed that morphological changes take place in blood coagula as a function of the velocity gradient at which such coagulation takes place. There is a progressive change from the red clot to white thrombus as the rates of shear increase. Aggregation of platelets increases as the rate of shear increases.This pattern is maintained with changes of temperature, although aggregation of platelets appears to be increased at elevated temperatures.Intravenously added heparin affects the clotting time and the aggregation of platelets in in vitro coagulation.

Occurrence of milk proteins in the urine of cows during an extended milking interval

1967 ◽  
Vol 34 (1) ◽  
pp. 27-30 ◽  
Author(s):  
R. L. J. Lyster ◽  
J. V. Wheelock
Keyword(s):  
Molecular Weight ◽  
Milk Proteins ◽  
Immunological Methods ◽  
Factors Affecting ◽  
Β Lactoglobulin

SummaryImmunological methods have been used to test samples of urine from 5 cows for the presence of milk proteins. None could be detected when the cows were milked twice daily at the usual intervals, but during an extended milking interval α-lactalbumin was found in the urine of all 5 cows and β-lactoglobulin in the urine of 2 cows. The urine of one cow during and after a milking interval of 39 h contained 1·63 g α-lactalbumin, 1·12 g β-lactoglobulin and a small amount of casein. One of the factors affecting the transfer of these milk constituents from the udder to the urine appears to be their molecular weight.

DRIED MILK POWDER: II. FACTORS AFFECTING THE SORPTION OF CARBON DIOXIDE

1945 ◽  
Vol 23f (6) ◽  
pp. 327-333 ◽  
Author(s):  
Jesse A. Pearce
Keyword(s):  
Carbon Dioxide ◽  
Milk Powder ◽  
Sorption Rate ◽  
High Fat ◽  
Time Intervals ◽  
Sorption Behaviour ◽  
Factors Affecting ◽  
Whole Milk ◽  
Identical Manner ◽  
Whole Milk Powder

Sorption of carbon dioxide by milk powder in a closed system at 35 °C. and at approximately 74 cm. of mercury was observed to be greater than 0.4 cc. per gm. after 150 hr., while only 0.012 cc. of nitrogen was absorbed per gm. after 70 hr. The initial sorption of carbon dioxide varied with time according to the equation:[Formula: see text]where s is 100 times the amount sorbed in cc. per gm. at any time, t (min.), and k and m are constants peculiar to the system under investigation. The logarithmic form of this equation was used. Powders with 26, 28, and 30% fat did not differ in behaviour, but sorption curves for powders with only 1% fat had lower [Formula: see text] values and lower [Formula: see text] values than the curves for the high fat levels. Powders with 1% fat sorbed carbon dioxide in an identical manner when exposed to either 100% carbon dioxide or a mixture of 20% carbon dioxide and 80% nitrogen. For whole milk powder, dilution to 80% nitrogen content was effective in reducing the initial sorption rate of carbon dioxide. Great variation was observed in the sorption behaviour of powders from different plants and in powders produced at different time intervals in the same plant. Temperature differences within the range 25° to 40 °C. had no effect on sorption. Palatability and [Formula: see text] correlated to the extent of r =.61.

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