Exploration of the mechanism of heavy coagulum formation in lactic casein manufacture: role of starter and an unidentified co-factor

1997 ◽  
Vol 64 (1) ◽  
pp. 69-75 ◽  
Author(s):  
MICHAEL G. WEEKS ◽  
EILEEN J. GOSLING ◽  
PETER A. MUNRO
Keyword(s):  
Whey Proteins ◽  
Skim Milk ◽  
Low Ph ◽  
Cottage Cheese ◽  
Heat Inactivation ◽  
Isoelectric Precipitation ◽  
Heat Stable ◽  
Slow Coagulation ◽  
Β Lactoglobulin

Heavy coagulum formation in lactic casein manufacture results in high casein concentration, high starter bacteria concentration and low pH on the base of the coagulation vessel. No heavy coagulum was formed during slow coagulation of skim milk with glucono-δ-lactone, indicating that starter bacteria were necessary. Skim milk preheat treatments severe enough to cause denaturation of the more heat- stable whey proteins, α-lactalbumin and β-lactoglobulin, also caused a reduction in heavy coagulum formation, suggesting the heat inactivation of a co-factor involved in the process. These results suggest a mechanism for heavy coagulum formation similar to that for minor sludge formation in cottage cheese manufacture. Starter bacteria would clump together, probably assisted by a co-factor. These starter clumps would generate a region of low pH causing isoelectric precipitation of casein in and around the clumps. The clumps would then settle forming a layer on the base of the coagulation vessel which might become further compressed by gravity.

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

2000 ◽  
Vol 67 (1) ◽  
pp. 31-42 ◽  
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.

scholarly journals Role of protein concentration and protein–saliva interactions in the astringency of whey proteins at low pH

2010 ◽  
Vol 93 (5) ◽  
pp. 1900-1909 ◽  
Author(s):  
M. Kelly ◽  
B. Vardhanabhuti ◽  
P. Luck ◽  
M.A. Drake ◽  
J. Osborne ◽  
...  
Keyword(s):  
Protein Concentration ◽  
Whey Proteins ◽  
Low Ph

Improvement of rheological properties of firm acid gels by skim milk heating is conserved after stirring

2003 ◽  
Vol 70 (4) ◽  
pp. 423-431 ◽  
Author(s):  
P Cayot ◽  
J-F Fairise ◽  
B Colas ◽  
D Lorient ◽  
G Brulé
Keyword(s):  
Storage Modulus ◽  
Skim Milk ◽  
Rheological Parameters ◽  
Water Retention Capacity ◽  
Gel Structure ◽  
Casein Micelles ◽  
Retention Capacity ◽  
Β Lactoglobulin

The enhancement of the strength of set acid gels by heating milk was related to rheological parameters (water retention capacity, storage modulus) of corresponding stirred gels. To obtain accurate rheological data from stirred gel it was necessary to maintain a constant granulometry of gel particles and to recognize time after stirring as a contributing factor. Two hours after stirring, the gel exhibited a higher storage modulus when milk was heated above 80 °C. A measurement of viscosity of just-stirred yoghurt was sufficient to predict correctly the quality of a stirred gel analysed by viscoelastic measurements. Increased resstance to syneresis of just-stirred gels was related to higher viscosity. The quantity of β-lactoglobulin (β-lg) bound to casein micelles explains the improvement of these gel qualities. We have considered that the structure of the initial firm gel (mesostructure level) was conserved in fragments within the stirred gel. Consequently, the explanation given by various authors for the effect of heating milk on the properties of set gels can also be applied to stirred gels. The same mechanism, described in literature for structure formation of set gels from acidified milk is purposed to explain the role of heating milk on the recovery of gel structure after stirring. The β-lg association with casein micelles during heating favoured micelle connections during the acidification. It also favoured the association of gel fragments after stirring during the recovery in gel structure.

scholarly journals On the role of peptide hydrolysis for fibrillation kinetics and amyloid fibril morphology

RSC Advances ◽  
2018 ◽  
Vol 8 (13) ◽  
pp. 6915-6924 ◽  
Author(s):  
Xinchen Ye ◽  
Mikael S. Hedenqvist ◽  
Maud Langton ◽  
Christofer Lendel
Keyword(s):  
Amyloid Fibril ◽  
Low Ph ◽  
Peptide Hydrolysis ◽  
Fibril Morphology ◽  
Β Lactoglobulin

Peptide hydrolysis determines the fibrillation rate and the morphology of amyloid-like nanofibrils formed by β-lactoglobulin at low pH.

Heat stability of plasmin (milk proteinase) and plasminogen

1986 ◽  
Vol 53 (2) ◽  
pp. 259-269 ◽  
Author(s):  
Efstathios Alichanidis ◽  
Julia H. M. Wrathall ◽  
Anthony T. Andrews
Keyword(s):  
Blood Plasma ◽  
Whey Proteins ◽  
Residual Activity ◽  
Skim Milk ◽  
Heat Stability ◽  
Heating Time ◽  
Heat Inactivation ◽  
Plasmin Activity ◽  
Sh Groups ◽  
Substrate Protection

SUMMARYThe effect of heating on plasmin activity in various media, including phosphate buffer pH 7·0, skim milk, blood plasma, solutions of casein and solutions of whey proteins were investigated. Plots of log residual activity υ. heating time were linear at all temperatures from 63 to 143 °C. In buffer solutions the presence of casein led to substantial substrate protection, the Arrhenius plots being linear both in the presence and absence of casein. The activation energy, Ea, for the inactivation reaction, was 62·4 kJ/mol in buffer alone and 58·4 kJ/mol with casein present at 25 mg/ml. In skim milk, despite the presence of casein at a similar concentration, plasmin was no more stable to heat than in buffer alone, and a curved Arrhenius plot was obtained indicating a more complex inactivation mechanism. Heating in the presence of proteins having free -SH groups accelerated the inactivation of plasmin. The role of -SH groups was confirmed by experiments with added α-lactalbumin, in which no free -SH groups occur, and reduced carboxymethylated β-lactoglobulin, both of which were without effect. In blood plasma, plasmin was less stable to heat than in buffer (pH 7·0) or in skim milk. Plasminogen behaved very similarly to plasmin either when activated to plasmin with urokinase before heating or when activated afterwards. A hypothesis is presented to describe the heat inactivation and denaturation of plasmin. Technologically important findings are that in skim milk plasmin was largely unaffected by pasteurization conditions and 30–40% of its activity remained even after ultra high temperature processing conditions.

Factors affecting the ethanol stability of bovine milk.: I. Effect of serum phase components

1981 ◽  
Vol 48 (2) ◽  
pp. 273-284 ◽  
Author(s):  
David S. Horne ◽  
Thomas G. Parker
Keyword(s):  
Whey Proteins ◽  
Bovine Milk ◽  
Skim Milk ◽  
Casein Micelles ◽  
Ph Profile ◽  
Factors Affecting ◽  
Milk Serum ◽  
Ethanol Stability ◽  
Serum Components

SummaryBy resuspending casein micelles in whey and dialysate it is shown that the role of whey proteins in the ethanol (EtOH)-induced coagulation of skim-milk is minimal. Experiments involving the interchange of milk sera indicated that the position of the EtOH stability/pH profile along the pH axis was governed by the diffusible constituents of the milk serum phase. The identities of those serum components governing the shape and position of the EtOH stability/pH profile were investigated. The addition of Ca2+ caused a shift in the entire profile to higher pH. Reduction of the available Ca2+ by addition of EDTA (up to 5 ran) shifted the profile to lower pH. The addition of phosphate (up to 5 mM) or citrate (up to 1 mM) had no effect on the profile, though higher concentrations of citrate (up to 5 mMi) caused slight shifts to lower pH. When equimolar amounts of Ca and phosphate were added, the system showed a shift in profile approximately equivalent to that of the free Ca introduced. Increasing the ionic strength of a milk by the addition of NaCl did not shift the profile, but decreased the maximum EtOH stability of the high pH arm of the sigmoidal profile. The EtOH stability/pH profile retained the same sigmoidal shape in all cases.

The Role of β-lactoglobulin in the primary phase of rennin action on heated casein micelles and heated milk

1974 ◽  
Vol 41 (3) ◽  
pp. 367-372 ◽  
Author(s):  
J. V. Wheelock ◽  
A. Kirk
Keyword(s):  
Heat Treatment ◽  
Complex Formation ◽  
Skim Milk ◽  
Primary Phase ◽  
Casein Micelles ◽  
Heated Milk ◽  
Β Lactoglobulin

SummaryIt has been shown that the inhibition caused by heat treatment, of the primary phase of rennin action on casein micelles, is dependent on the presence of β-lactoglobulin. The degree of inhibition increased with increasing amounts of added β-lactoglobulin for both heated casein micelles and heated skim-milk to a constant value. The results are fully consistent with the hypothesis that the inhibition is caused by complex formation between β-lactoglobulin and κ-casein when milk is heated.

The quantitative measurement of whey proteins using polyacrylamide-gel electrophoresis

1976 ◽  
Vol 43 (2) ◽  
pp. 259-265 ◽  
Author(s):  
Robyn M. Hillier
Keyword(s):  
Gel Electrophoresis ◽  
Protein Denaturation ◽  
Quantitative Estimation ◽  
Polyacrylamide Gel Electrophoresis ◽  
Whey Proteins ◽  
Skim Milk ◽  
Internal Standard ◽  
Polyacrylamide Gel ◽  
Native Whey ◽  
Β Lactoglobulin

SummaryA method is described for the quantitative estimation of a mixture of whey proteins by spectrophotometric scanning of the stained protein bands following polyacrylamide-gel electrophoresis. The incorporation of β-lactoglobulin A as an internal standard improves the accuracy of the technique. The method has been used to measure residual native whey proteins in milk after heating. Results are presented for whey protein denaturation in skim-milk after heat treatment at 130 and 140 °C for various periods of time.

scholarly journals Anti-Diabetic Activity of Whey Proteins

2020 ◽  
Vol 50 (2) ◽  
pp. 306-318
Author(s):  
E. Agarkova ◽  
Ksenia A Ryazantseva ◽  
A. Kruchinin
Keyword(s):  
Inhibitory Activity ◽  
Whey Proteins ◽  
Biologically Active ◽  
Cottage Cheese ◽  
Processing Technologies ◽  
Dpp Iv ◽  
Ic50 Value ◽  
Inhibitory Potential ◽  
Β Lactoglobulin ◽  
Hydrolysis Of

Absract. Introduction. With the advent of membrane filtration technologies, milk whey stopped being a “by-product” of cheese, cottage cheese, and casein production. The combination of various whey-processing technologies, e.g. enzymatic hydrolysis and membrane fractionation, made it possible to obtain concentrates, isolates, and hydrolysates of whey proteins with various biologically active effects. Study objects and methods. The article features research results of Russian and foreign scientific teams in the development of functional antidiabetic ingredients from hydrolyzed proteins of milk and whey. Results and discussion. According to foreign studies, Ile-Pro-Ile (diprotin A) with an IC50 value of 4.7 μM is one of the most effective low molecular mass peptides with an inhibitory potential against DPP-IV. Various studies of trypsin hydrolysis of β-lactoglobulin described the production of IPAVF peptide fragment with the most potent inhibitory activity of DPP-IV (IC50 = 44.7 μM). Other studies featured pepsin-treated lactoglobulin production of fragments LKPTPEGDL and LKPTPEGDLEIL with inhibitory activity DPP-IV IC50 = 45 and 57 μM, respectively. A number of studies described similar fragments obtained by the sequential action of the enzyme preparation Neutrase 0.8 LTM on β-lactoglobulin, followed by pepsin hydrolysis. As for the hydrolysis of α-lactalbumin with pepsin, scientists identified peptides WLAHKALCSEKLDQ, LAHKALCSEKL, and TKCEVFRE. They revealed a high inhibitory potential against DPP-IV (IC50 = 141, 165, and 166 μM, respectively). Tryptic hydrolysates of bovine β-lactoglobulin proved to be able to inhibit DPP-IV in vitro (IC50 of 210 μM). Peptide VAGTWY was the major compound responsible for this effect, displaying an IC50 of 174 μM. In other research, tryptic hydrolysate inhibited DPP-IV with an IC50 value of 1.6 mg/mL, also demonstrating antioxidant and ACE-inhibitory activities. This hydrolysate became source of VAGTWY, the most potent DPP-IV inhibitor (IC50 of 74.9 μM). Conclusion. An analysis of Russian and foreign studies proved that milk protein hydrolysis has a great potential for antidiabetic additives used in the treatment of type II diabetes. This are requires further research in order to define the safety of biologically active peptides.

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