Casein preparation from milk

Products prepared from soy protein products and resembling chicken, ham, frankfurters, and bacon are available commercially. Soy protein isolates are used in place of milk proteins or sodium caseinate in products such as coffee creamers, whipped toppings, yogurt, and infant formulas (see Dairy substitutes). Soy protein products also are used in snacks and in baked foods. 

Feeding studies with the rat as the test animal verified the high nutritional quality indicated by the amino acid pattern (45). Using isolates and concentrates prepared from Jewel and Centennial cultivars, PER values were equal to that of casein (milk protein) (Table IV). Examination of the amino acid patterns of sweet potato protein and casein revealed that both contained... 

In contrast to the caseins, the whey proteins do not precipitate from solution when the pH of milk is adjusted to 4.6. This characteristic is used as the usual operational definition of casein. This difference in the properties of the two milk protein groups is exploited in the preparation of industrial casein and certain varieties of cheese (e.g. cottage, quarg and cream cheese). Only the casein fraction of milk protein is normally incorporated into these products, the whey proteins being lost in the whey. 

Because they occur as large aggregates, micelles, most (90-95%) of the casein in milk is sedimented by centrifugation at 100000 g for 1 h. Sedimentation is more complete at higher (30-37°C) than at low (2°C) temperature, at which some of the casein components dissociate from the micelles and are non-sedimentable. Casein prepared by centrifugation contains its original level of colloidal calcium phosphate and can be redispersed as micelles with properties essentially similar to the original micelles. 

Higashio, K. and Yoshioka, Y. 1981C. Studies on milk clotting enzyme from microorganisms. III. Breakdown of casein fractions by milk clotting enzyme preparations of Mucor recemosus No. 50 and its mutants. J. Agric. Chem. Soc. Japan 55, 951-958. 

To study the clotting of micellar casein skim milk prepared from low-heat skim milk powder was diluted 16 times with 0.01 M CaCl2, to which NaCl was added to adjust the ionic strength. 

Primary Mode of Reaction and Consequences (9). Bovine a8i-casein (Variant B) was prepared from fresh milk (12) and immediately succinylated to increase water dispersibility (13). This succinylated asi-casein preparation, molecular weight of ca. 25,000 daltons, was used as the hydrophilic protein substrate. The compound L-norleucine 1-13C-dodecyl ester, prepared from K13CN and 1-bromoundecane through four steps (14,15,16), was used as the lipophilic nucleophile. C-13 NMR measurements showed that this sample gave only one signal at a distance of 65.2 ppm from the signal of tetramethylsilane (TMS). 

MUk coagulation depends on a number of factors, such as the kinetics of the enzyme reaction, the concentration, and the state of the proteins, especially casein, the balance of minerals, especially calcium, and pH [101]. Most of these factors are directly influenced by UF or MF processing. Caron et al. [101] compared the rennet coagulation properties of nfilk enriched with a regular ultrafiltered retentate powder (RUF) to milk enriched with a diafiltered MF (DMF) retentate powder. RUF was prepared by concentrating skim milk to concentration factor of 5 by UF, while DMF was prepared from skim nfilk concentrated... 

A) Preparation of Casein from Milk. To 40 ml of milk in a 250 ml beaker, add 40 ml of water and five drops of 6iV acetic acid. The coagulated protein to which the fat adheres settles out. Filter the precipitate and wash it with water twice, so that it collects at the lower point of the folded filter paper. When most of the water has drained, remove the filtrates if it is desired to isolate the lactose. Wash twice with a 5 ml portion of alcohol and then twice with a 5 ml portion of ether. Collect the alcohol and ether washings separately and place them in a bottle provided for this... 

Augmentation of the Ca reservoir in plaque can also be provided by casein phosphopeptide preparations. Such materials, derived from milk, can bind amorphous CaPi and have been shown to inhibit demineralisation [51] and promote remineralisation [52] of enamel in situ in humans. Rose [53] recently demonstrated that the addition of casein phosphopeptide to a model bacterial plaque in vitro not only provided extra Ca2+-binding sites but also restricted Ca diffusion through the plaque. 

Sample Preparation for CE. To dissociate the caseins, all samples were dissolved in a sample buffer containing 8M urea and 10 mM dithiothrei-tol at pH 8, and left for at least Ih at room temperature before filtration (0.22 pm Millex-GVi3, MilUpore) and CE analysis. The isoelectrically precipitated casein from milk and cheese and the purified casein standards were dissolved at lOmg/mL. To most samples, IpL of additional tripeptide Lys-Tyr-Lys (50mg/mL) was added per 50pL of sample as a reference compound. 

NaCl. The / -casein was prepared from the skimmed milk of a single homozygous cow (aslB, /JB, kB).7 Guanidine hydrochloride (Pierce, Sequanal Grade) was purified from some surface-active compounds by several crystallizations in water. 

The development of large-pore membranes facilitates the separation of whey proteins from casein micelles by microfiltration (MF). Membranes used in MF have cut-offs in the range 0.01-10/im, and therefore casein micelles may be in the permeate or retentate streams, depending on the pore size of the MF membranes chosen. MF with large-pore membranes very effectively removes bacteria and somatic cells from milk and may also be used to remove lipoprotein complexes from whey prior to the production of WPCs with improved functionality. The preparation of micellar casein by MF is still at the exploratory stage. 

Rennet is used extensively in the production of cheese. This enzyme is found in the fourth stomach of the calf it converts casein into paracasein, which, in the presence of calcium, precipitates to form an elastic curd. Much commercial rennet is contaminated with pepsin which tends to act strongly on casein and thereby produces a weak curd with off flavor. Many microbial proteases can clot milk, but only recently have microbial preparations been produced which can replace calf rennet to prepare cheeses of good flavor. Microbial preparations from Endothia parasitica and Mucor pusillus var. Lindt seem to be the most promising, and these have been used commercially. The new sources of rennet were reviewed recently (Sardinas, 1969). 

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