Coagulation time

Review biopsy reports and laboratory data. Transaminases and blood ammonia levels do not correlate well with disease progression, but increased coagulation times are markers of loss of synthetic function. 

It is reasonable to assume, at least for oppositely charged polymers and particles, that aA > ag, which means that the adsorption time is always expected to be shorter than the coagulation time under perikinetic conditions. Consequently, perikinetic flocculation rates are very likely not to be adsorption rate limited. The ratio of orthokinetic adsorption time to orthokinetic coagulation time is... 

Wu H, Ye DJ, Zhao YZ, Wang SL. (1993). [Effect of different preparations of ginger on blood coagulation time in mice]. Chung Kuo Chung Yao Tsa Chih. 18(3) 147-9, 190. 

Casein is low in sulphur (0.8%) while the whey proteins are relatively rich (1.7%). Differences in sulphur content become more apparent if one considers the levels of individual sulphur-containing amino acids. The sulphur of casein is present mainly in methionine, with low concentrations of cysteine and cystine in fact the principal caseins contain only methionine. The whey proteins contain significant amounts of both cysteine and cystine in addition to methionine and these amino acids are responsible, in part, for many of the changes which occur in milk on heating, e.g. cooked flavour, increased rennet coagulation time (due to interaction between /Mactoglobulin and K-casein) and improved heat stability of milk pre-heated prior to sterilization. 

Figure 9.7 The pH of samples of milk after heating for various periods at 130°C with air (O). 02 ( ) or N2 (A) in the headspace above the milk t, coagulation time (from Sweetsur and...

Figure 9.21 Effect of pressure (Rannie homogenizer) on the heat coagulation time (at 140°C) of milk, unhomogenized ( ) or homogenized at 3.5 MPa (A) 10.4 MPa ( ) or 20.7/3.5 MPa ( + ) (from Sweetsur and Muir, 1983).

Measurement of rennet coagulation time. A number of principles are used to measure the rennet coagulability of milk or the activity of rennets most measure actual coagulation, i.e. combined first and second stages, but some specifically monitor the hydrolysis of K-casein. The most commonly used methods are described below. 

Figure 10.4 Principal factors affecting the rennet coagulation time (RCT) of milk.

Vitamin K A. plays an essential role in preventing thrombosis. B. increases the coagulation time in newborn infants with hemorrhagic disease. C. is present in high concentration in cow or breast milk. D. is synthesized by intestinal bacteria. E. is a water-soluble vitamin. Correct answer = D. Vitamin K is essential for clot formation, decreases coagulation time, and is present in low concentrations in milk. 

Storch and Segelcke (1874) proposed that the product of coagulation time (tc) and enzyme concentration (E) should be defined as a constant (k) (McMahon and Brown 1983, 1984B). 

Figure 12.3 Plot of apparent absorbance (600nm) versus time after addition of chymosin to reconstitute nonfat dry milk (12g + 100 ml.OIM CaCe2). Arrows represent Formagraph coagulation time. Inset shows an expanded view of the first 3 min of coagulation. (From McMahon et at. 1984)...

Brown, R. J. and Collinge, S. K. 1986. Actual milk coagulation time and inverse of chy-mosin activity. J. Dairy Sci. 69, 956-958. 

Dalgleish, D. G. 1980. Effect of milk concentration on the rennet coagulation time. J. Dairy Res. 47, 231-235. 

McMahon, D. J. Richardson, G. H. and Brown, R. J. 1984C. Enzymic milk coagulation Role of equations involving coagulation time and curd firmness in describing coagulation. J. Dairy Sci. 67, 1185-1193. 

Payens, T. A. 1984. The relationship between milk concentration and rennet coagulation time. J. Appl. Biochem. 6, 232-239. 

The casein micelles become surrounded by whey proteins and cannot interact with one another, thus reducing whey syneresis. This results in a soft curd that retains more moisture. The yield of cheese is increased due to the incorporation of whey proteins and the higher moisture content. Overheated milk requires longer rennet coagulation times. If milk is heated for 30 min at 75° C, it will not clot at all (Ustu-nol and Brown 1985). 

The proteolytic systems of psychrotrophic bacteria selectively attack /3- and as-caseins (Cousin and Marth 1977A), whereas whey proteins are relatively unaffected. Growth of psychrotrophic bacteria in milk results in decreased stability of casein, as measured by rennet coagulation time and heat stability (Cousin and Marth 1977B). Growth of psychrotrophs in milk also causes an increased rate of acid production by starter cultures as a result of increased quantities of readily available nitrogen compounds (Cousin and Marth 1977C.D). 

Other surface modification reactions that are relevant to biological studies include the binding of the blood anticoagulent, heparin,189 and of dopamine190 to polyphosp-hazene surfaces. The heparin immobilization brought about a five-fold increase in the coagulation time of blood, and the immobilized dopamine generated the same response in rat pituitary cells as did free dopamine. 

Blood coagulation Rabbit Oral Coagulation time, clot retraction, prothrombin time... 

Eriksson UG, Mandema JW, Karlsson MO, et al, Pharmacokinetics of melagatran and the effect on ex vivo coagulation time in orthopaedic surgery patients receiving subcutaneous melagatran and oral ximelagatran a population model analysis. Clin Pharmacokinet 2003 42 687-701. 

Fig. 10. Logarithm of the coagulation time as a function of the net protein charge (Q in the figure, Z in the text) for fluorescamine-treated caseins at different Ca2+ concentrations. From Horne (1983), reproduced by permission of the publishers, Butterworth-Heineman Ltd.

It has been shown that thixotropic gelation is a slow coagulation. Time of solidification is also changed with a change in the pH of the solution as mentioned by Freundlich. It is seen that alcohol promotes the thixotropic gelation and after evaporating the alcohol, the sol returns to the gel state. 

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