Variation in size of goat milk casein micelles related to casein genotype

SummaryWhole milk was concentrated by ultrafiltration in a plant causing some homogenization of the fat. Comparisons were made with milk concentrated in a plant causing little homogenization and with milk homogenized conventionally. None of the processes appreciably affected the casein micelle size distribution. On rennet treatment of homogenized milk, casein micelle aggregation occurred more slowly, the protein network in the curd was less coarse and the rate of whey loss was reduced, compared with non-homogenized milk at the same concentration. In using concentrated milks for cheesemaking homogenization improved the composition of Cheddar cheese, because of increased fat and moisture retention, but curd fusion was poorer. Some aspects of the texture of the mature cheeses were improved, but the free fatty acid levels were higher. Values for the firmness of curds, formed from milks processed in different ways, did not relate to the extent of aggregation of the casein micelles. It is suggested that the complete cheesemaking process is driven by the tendency of the casein to aggregate.

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High-pressure treatment of milk: effects on casein micelle structure and on enzymic coagulation

Journal of Dairy Research ◽

10.1017/s0022029999004021 ◽

2000 ◽

Vol 67 (1) ◽

pp. 31-42 ◽

Cited By ~ 130

Author(s):

ERIC C. NEEDS ◽

ROBERT A. STENNING ◽

ALISON L. GILL ◽

VICTORIA FERRAGUT ◽

GILLIAN T. RICH

Keyword(s):

Whey Proteins ◽

Skim Milk ◽

Casein Micelle ◽

Casein Micelles ◽

Dense Networks ◽

Protein Levels ◽

Micelle Structure ◽

Milk Casein ◽

Β Lactoglobulin ◽

Gel Network

High isostatic pressures up to 600 MPa were applied to samples of skim milk before addition of rennet and preparation of cheese curds. Electron microscopy revealed the structure of rennet gels produced from pressure-treated milks. These contained dense networks of fine strands, which were continuous over much bigger distances than in gels produced from untreated milk, where the strands were coarser with large interstitial spaces. Alterations in gel network structure gave rise to differences in rheology with much higher values for the storage moduli in the pressure-treated milk gels. The rate of gel formation and the water retention within the gel matrix were also affected by the processing of the milk. Casein micelles were disrupted by pressure and disruption appeared to be complete at treatments of 400 MPa and above. Whey proteins, particularly β-lactoglobulin, were progressively denatured as increasing pressure was applied, and the denatured β-lactoglobulin was incorporated into the rennet gels. Pressure-treated micelles were coagulated rapidly by rennet, but the presence of denatured β-lactoglobulin interfered with the secondary aggregation phase and reduced the overall rate of coagulation. Syneresis from the curds was significantly reduced following treatment of the milk at 600 MPa, probably owing to the effects of a finer gel network and increased inclusion of whey protein. Levels of syneresis were more similar to control samples when the milk was treated at 400 MPa or less.

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Effect of Temperature, pH, Enzyme to Substrate Ratio, Substrate Concentration and Time on the Antioxidative Activity of Hydrolysates from Goat Milk Casein by Alcalase

Acta Universitatis Cibiniensis Series E Food Technology ◽

10.1515/aucft-2016-0013 ◽

2016 ◽

Vol 20 (2) ◽

pp. 29-38 ◽

Cited By ~ 5

Author(s):

Guowei Shu ◽

Bowen Zhang ◽

Qian Zhang ◽

Hongchang Wan ◽

Hong Li

Keyword(s):

Substrate Concentration ◽

Superoxide Radical ◽

Radical Scavenging Activity ◽

Radical Scavenging ◽

Goat Milk ◽

Scavenging Activity ◽

Antioxidant Peptides ◽

Hydrolysis Time ◽

Hydrolysis Temperature ◽

Milk Casein

Abstract The effect of hydrolysis temperature (45, 50, 55, 60 and 65°C), pH (7.0, 7.5, 8.0, 8.5 and 9.0), enzyme to substrate (E/S) ratio (1.0, 1.5, 2.0, 2.5 and 3.0%), substrate concentration (2, 3, 4, 5 and 6%) and hydrolysis time (30-240min) on antioxidant peptides hydrolysated from goat’s milk casein by Alcalase was investigated using single factor experiment. In order to obtain high DPPH radical-scavenging activity, metal-chelating activity and superoxide radical scavenging activity, the optimal conditions were hydrolysis time of 150 min, temperature of 50°C, pH 8.0, E/S ratio of 2.0% and substrate concentration of 4.0%. The hydrolysis time, hydrolysis temperature, pH, E/S ratio and substrate concentration had a significant influence on degree of hydrolysis, metal-chelating activity, DPPH and superoxide radical scavenging activity on casein hydrolysate of goat milk by Alcalase, the results were beneficial for further provide theoretical basis for production of antioxidant peptides.

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Molecular weight and size distribution of bovine milk casein micelles

Biochimica et Biophysica Acta (BBA) - Protein Structure ◽

10.1016/0005-2795(74)90086-5 ◽

1974 ◽

Vol 342 (2) ◽

pp. 313-321 ◽

Cited By ~ 29

Author(s):

R.K. Dewan ◽

A. Chudgar ◽

R. Mead ◽

V.A. Bloomfield ◽

C.V. Morr

Keyword(s):

Molecular Weight ◽

Size Distribution ◽

Bovine Milk ◽

Casein Micelles ◽

Milk Casein

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Protein-polyphenol reactions

British Journal Of Nutrition ◽

10.1079/bjn19820027 ◽

1982 ◽

Vol 47 (2) ◽

pp. 191-211 ◽

Cited By ~ 77

Author(s):

R. F. Hurrell ◽

P. A. Finot ◽

J. L. Cuq

Keyword(s):

Caffeic Acid ◽

Goat Milk ◽

Lysine Content ◽

Reaction Products ◽

Protein Ratio ◽

Alkaline Conditions ◽

Available Lysine ◽

Sunflower Protein ◽

Milk Casein ◽

Net Protein

1. Studies were made on the lysine content of casein reacted with caffeic acid oxidized aerobically under alkaline conditions or enzymically with tyrosinase (EC 1.14.18.1).2. Loss of fluorodinitrobenzene (FDNB)-reactive lysine was rapid at pH 10 and increased with time and the temperature of the reaction, with concentration of caffeic acid and with the oxygenation of the mixture. In presence of the enzyme mushroom tyrosinase, maximum reduction of reactive lysine occurred at pH 7 and was dependent on the reaction time and on the concentration of caffeic acid.3. Reaction of α-formyl-L-[U- 14C]lysine with caffeic acid at pH 10 showed the rapid formation of five reaction products which appeared to polymerize gradually as the reaction progressed.4. The nutritionally available lysine content of the casein-caffeic acid mixtures, as assayed with rats, was reduced after both alkaline and enzymic reactions, as were faecal digestibility, net protein ratio and net protein utilization. Biological value however was not reduced.5. In metabolic studies using goat milk casein labelled with L-[3H]lysine and reacted with caffeic acid in the same way, the lysine–caffeoquinone reaction products were not absorbed by the rat but were excreted directly in the faeces.6. The importance of the reaction of proteins with caffeoquinone and chlorogenoquinone (formed by the oxidation of caffeic and chlorogenic acids respectively) is discussed in relation to the production of sunflower protein, leaf protein and other vegetable-protein concentrates.

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