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

Abstract

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.

Heat stability of concentrated milk: enhancement of initial heat stability by incorporation of food grade lecithin

“…The concentration of total and soluble calcium in milk and ultrafiltrate as estimated with a Corning 940 calcium analyser (Corning Ltd, Halstead, U.K.) and that of inorganic phosphate by the method of Allen (1940) as modified by White & Davies (1958).…”

The measurement and significance of ionic calcium in milk – A review

“…White and Davies (1958c) found that rennet coagulation time (RCT) for bulked milk samples ranged between 3.2 and 5.4 min; for milk from individual cows (1.4–12.9 min) with a few samples which did not coagulate. The property which related most to RCT was pH.…”

Some Properties of Soured and De-Acidified Buffalo's Milk ? Mineral Composition

“…Heat Stability of Milk. The heat stability of milk was determined by heat coagulation time of milk heated to 130f 1 "C. The HCT of samples of normal milk, acidic milk and de-acidic milk were measured with an equipment using the procedure based on White and Davies (1958). Milk samples in duplicate of 5 ml volume were pipetted into two clean, dry and thick walled corning glass tubes (or 10 ml capacity, and dimensions of 15 mm diameter and 125 mm height) provided with tightly stoppered screw caps fitted with tigon washers.…”