In order to determine the effect of lipid concentration on the properties of k-casein stabilized emulsions, butteroil was added to solutions that contained 0.3% k-casein to achieve milk fat concentrations of 3, 10, and 20%. These mixtures were adjusted to pH 6.5 and heated to 65°C. They were then homogenized at 20 and 100 MPa and particle size was measured; viscosity and yield stress were measured before and 30 minutes after the addition of chymosin. These experiments were repeated twice. Homogenization of the emulsions at 100 MPa produced smaller particles than homogenization at 20 MPa. Emulsions with 20% milk fat showed the largest particle size. Before treated with chymosin, these emulsions had the greatest viscosity and yield stress, however the differences with the other lipid concentrations were greater after chymosin treatment. A gel with yield stress less than 10 Pa occurred in emulsions with 3 or 10% milk fat. The emulsion with 20% milk fat after chymosin treatment provided the best possibility for the formation of a gel because it had the highest viscosity and yield stress. The effect of protein concentration on the properties of the emulsions was determined in emulsions that contained 20% milk fat and 0.5, 0.7, and 1.0%. These emulsions were prepared as previously described. Emulsions homogenized at 100 MPa had smaller particles than emulsions homogenized at 20 MPa. An increase in protein concentration caused the particle size to decrease. Emulsions homogenized at 100 MPa were more stable than emulsions homogenized at 20 MPa and the emulsion with 1.0% k-casein was the most stable emulsion. The protein load of k-casein stabilized emulsions ranged from 3 to 6 mg/m2. The viscosity and yield stress prior to chymosin treatment showed no properties of gelation. After treated with chymosin, these emulsions produced a weak gel with yield stress values that ranged from 14 to 16 Pa.

Thesis--M.D.S., University of Hong Kong, 1987.

k-Casein which was electrophoretically (Starch gel) homogeneous was hydrolyzed with the enzyme Pronase P and the resultant hydrolyzate was fractionated by column chromatography. A fraction, rich in carbohydrate, was isolated by use of Sephadex G-25. Analysis showed that it contained at least nine different components. Another fraction was isolated by use of Sephadex G-50. Chromatographic, electrophoretic and ultracentrifugal analysis indicated that this fraction contained a single glycopeptide. The glycopeptide contained galactosamine (25.1%), galactose (22.1%) and sialic acid (16.6%), it has no N-term1nal amino acid and has serine as the C-terminal amino acid. Calculation based on the numbers of amino acid residues showed that the molecular weight of the glycopeptide was 11,300. [...]

This thesis is an investigation of binding of casein micelles to polyphenols such as epigallocatechin gallate (EGCG), resveratrol, and curcumin. The incorporation of the bioactive molecules in casein micelles seems to be beneficial. The results from this study clearly demonstrated that casein micelles can incorporate polyphenols. There is a difference in the binding behaviour between curcumin and resveratrol. Curcumin is able to penetrate the core of the micelles, but resveratrol has less affinity for the hydrophobic sites, instead, it can be bind in the core of the micelles through the water channels. The processing of milk (heating, cooling, static high pressure and microfluidization) alters the surface or the internal structure of the casein micelles resulting in increased incorporation. The release of β-casein caused alteration to the core of the casein micelles, without any effect on the colloidal calcium phosphate composition and any changes in the surface properties of the micelles. These internal rearrangements lead to an increase in the affinity of the hydrophobic sites for curcumin and resveratrol in the inner core of the micelles. This work clearly confirmed that β -casein plays a role in stabilizing internal structures in the casein micelle and its release causes an increase in the micellar size by increasing the hydration and repulsion occurring within the water pockets present in the inhomogeneous inner structure of the casein micelles. Inner core of casein micelles undergoes rearrangements during application of static high pressure and microfluidization. In the case of static high pressure, the results indicated that the persistent rearrangement of the amino acid residues induced by high-pressure treatment result in an increase in the amount of curcumin association with milk proteins. It was shown that in both untreated and microfluidized milk, the presence of polyphenol molecules significantly affects rennet induced gelation, by delaying the gelation. However, the behavior of casein micelles incorporated with resveratrol is different comparing to curcumin, as resveratrol strongly affected the surface interactions during rennet-induced gelation. Further research is needed to explain the practical aspect ( functionalities such as acid gelation, emulsification and foaming) of application of casein micelles as natural nanocarrier of bioactive compounds. / The National Sciences and Engineering Research Council (NSERC),The Ontario Dairy Council.

A study was conducted to determine the relationship between the degree of glycosylation of $ kappa$-casein (CN) and physicochemical properties of milk: heat stability and ethanol stability. Morning milk samples from individual Holstein cows (genotype $ kappa$-CN AA, $ beta$-CN A$ sb1$A$ sb2$, $ alpha sb{ rm s1}$-CN BB, $ beta$-lactoglobulin AB) in midlactation were collected and analyzed for protein and somatic cell count. Samples of low somatic cell count ($<$150000 cells/ml) were skimmed and dialyzed overnight at 4$ sp circ$C against bulk tank milk to equilibrate soluble components. Three series of analyses were performed for the determination of thermostability of milk between pH 6.5 and 9. In the first 2 sections (A and B), the heat clotting time vs pH (HCT/pH) profiles of normal milk were measured. The effect of sialic acid (NANA) depletion on the HCT/pH profile was tested in a third series of experiments. And finally, a series of analyses were performed to determine the ethanol stability of milk. (Abstract shortened by UMI.)

Preliminary experiments indicated that an acid casein co-precipitate could be produced by extrusion from skim milk powder (SMP). In assessing the problems encountered, experiments were designed to model and optimize the coagulation/washing process using response surface methodology (RSM), to minimize residual whey components and losses of fines. This study yielded useful information relative to improving our understanding of the coagulation mechanism and the most important variables affecting the process. In addition, RSM allowed multiresponse optimization of acid casein production using unique and newly developed optimization techniques. In order to simplify the process, an extruder die was designed to assist with the dewheying process, however, plugging problems occurred due to screw design limitations. Studies were implemented to determine the rheological behaviour of sodium caseinate and to evaluate the extruder performance in terms of energy consumption, and in terms of mixing and conveying through mathematical description of residence time distributions in the extruder. The knowledge gained from these studies was integrated to produce acid casein and sodium caseinate at pilot plant level and to conceive a plant layout of the process for the dairy industry. The process developed has many advantages, including the ability to produce a high quality product.

The purpose of this investigation was to study the role of pectin in protecting casein from coagulation by heat and acid during the preparation of tomato soup. Three varieties of tomatoes were used for the study, Ace, Improved Garden State and Campbell 146, and each variety was processed two ways, by heating the tomatoes rapidly to 100°C before juicing (hot break) and by holding the mascerated tomatoes for 30 minutes before heating (cold break). Juice of the Ace variety had the highest pH and Campbell 146 the lowest by both processing methods. In all cases, cold break juice had lower pH values than did the hot break juice. Proportion of serum to solids resulting from centrifugation of a sample of each juice was used as one index to the amount of degradation of the pectin. The amount of solids in the cold break juice was less than the amount of solids in the hot break juice. Serums from juices prepared by the hot break method were more viscous than those by the cold break method. Of the hot break juices, Improved Garden State was the most viscous and Campbell 146 the least. The concentration of pectin in the serums of juices prepared by the cold break method was from one-third to one-half that in serums of juices by the hot break method. Juices of the three varieties of tomatoes by both methods of processing were combined with reconstituted non-fat milk and heated as for tomato soup. Curdling was assessed by measuring the nitrogen in the filtrate by the micro-Kjeldahl method. Juices of Ace, the low acid variety, caused the least amount of curdling. Of the four juices from the two more acid varieties, Campbell 146 by the cold break method had the lowest concentration of pectin in the serum and the soup curdled most, while Improved Garden State by the hot break method was highest in pectin and resulted in the least curdling of the soup. Juice from Campbell 146 by the cold break method was the most acid of the four and that of Improved Garden State by the hot break method was the least acid. When an amount of high-methoxy pectin equal to the difference between the concentration of pectin in the cold break and that in the hot break juices of the Improved Garden State variety was added to a sample of the juice before making soup, curdling was less than when untreated juice was used, and the pH was slightly higher. Thus any protective effect that pectin might have had. on the casein was clouded by differences in the pH values of the juices. Pectin possibly has a role in protecting the casein, but the acidity certainly is the determining factor in the coagulation of casein in the preparation of tomato soup. / Graduation date: 1963

Thesis (M. D. S.)--University of Hong Kong, 2006. / Also available in print.

Thesis (Ph. D.)--Ohio State University, 2004. / Document formatted into pages; contains 150 p. Includes bibliographical references. Abstract available online via OhioLINK's ETD Center; full text release delayed at author's request until 2005 Sept. 7.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 64-67.