Whey Proteins: Functionality and Foaming under Acidic Conditions

Selective thermal precipitation followed by a mechanical separation step is a well described method for fractionation of the main whey proteins, α-lactalbumin (α-la) and β-lactoglobulin (β-lg). By choosing appropriate environmental conditions the thermal precipitation of either α-la or β-lg can be induced. Whereas β-lg irreversibly aggregates, the precipitated α-la can be resolubilized by a subsequent adjustment of the solution’s pH and the ionic composition. This study reports on the analytical characterization of resolubilized α-la compared to its native counterpart as a reference in order to assess whether the resolubilized α-la can be considered close to ‘native’. Turbidity and quantification by RP-HPLC of the resolubilized α-la solutions were used as a measure of solubility in aqueous environment. RP-HPLC was also applied to determine the elution time as a measure for protein’s hydrophobicity. DSC measurement was performed to determine the denaturation peak temperature of resolubilized α-la. FTIR spectroscopy provided insights in the secondary structure. The refolding of α-la achieved best results using pH 8.0 and a 3-fold stoichiometric amount of Ca2+ per α-la molecule. The results showed that the mechanism of aggregation induced by gentle thermal treatment under acidic conditions with subsequent mechanical separation is reversible to a certain extent, however, the exact native conformation was not restored.

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Heat stability improvement of antimicrobial whey proteins fromyak milk and colostrum at various acidic conditions

Asian Journal of Dairy and Food Research ◽

10.18805/ajdfr.v3i1.3570 ◽

2016 ◽

Vol 35 (3) ◽

Cited By ~ 1

Author(s):

Shimo Peter Shimo ◽

W U Xiaoyun ◽

Ding Xuezhi ◽

Yan Ping

Keyword(s):

Whey Proteins ◽

Sodium Dodecyl ◽

Heat Stability ◽

Heat Denaturation ◽

Percentage Reduction ◽

Processing Conditions ◽

Yak Milk ◽

Acidic Conditions ◽

The Mean ◽

Mean Concentration

The aim of this study was to characterize the effect of heat denaturation on Immunoglobulin G (IgG) and Lactoferrin (LF) in yak milk and colostral liquid whey at medium acidic conditions in presence of protectants (CaCl2; Glycerol and Sodium Dodecyl Sulphate - SDS). Results indicated significant (P less than 0.05) heat stability improvement of IgG and LF in liquid whey samples at medium acidic and temperature (72 - 90oC) with less precipitates formation regardless of type of protectants added especially at pH 3.5 and 4.6. The mean concentration values for IgG percentage reduction (72 – 90oC; pH 3.5 – 5.5; protectants) ranged from 6 to 26% and 15 to 31% in yak milk and colostral liquid whey, respectively. The percentage of heat denaturation effect for LF ranged from 11 to 32%t and 14 to 38% in yak milk and colostral liquid whey, respectively. Application of glycerol in both environmental processing conditions was the most effective in heat stability improvement followed by SDS and CaCl2.

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0513 Effect of γ radiation on physicochemical properties, protein-protein interaction, and microstructure of whey proteins

Journal of Animal Science ◽

10.2527/jam2016-0513 ◽

2016 ◽

Vol 94 (suppl_5) ◽

pp. 246-246

Author(s):

M. Guo ◽

X. Wang ◽

F. Lee ◽

J. Lv ◽

D. Zhang

Keyword(s):

Physicochemical Properties ◽

Protein Interaction ◽

Whey Proteins ◽

Γ Radiation ◽

Protein Protein Interaction

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Application of whey proteins microparticulate in the technology of kefir production

Dairy Industry ◽

10.31515/1019-8946-2018-8-49-51 ◽

2018 ◽

pp. 49-51

Author(s):

E.B. Stanislavskaya ◽

◽

E.I. Melnikova ◽

Keyword(s):

Whey Proteins

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Prospects of using dynamic membrane filtration module UF-RDM for concentrating cheese whey proteins

Сheesemaking and buttermaking ◽

10.31515/2073-4018-2019-6-54-56 ◽

2019 ◽

Vol 56 (6) ◽

pp. 54-56

Author(s):

E.Yu. Agarkova ◽

◽

A.G. Kruchinin ◽

A.A. Agarkov ◽

V.D. Haritonov

Keyword(s):

Membrane Filtration ◽

Cheese Whey ◽

Whey Proteins ◽

Dynamic Membrane

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Nε-Acetyl L-α Lysine Improves Activity and Stability of α-Amylase at Acidic Conditions: A Comparative Study with other Osmolytes

Protein and Peptide Letters ◽

10.2174/0929866526666191105130041 ◽

2020 ◽

Vol 27 (6) ◽

pp. 551-556

Author(s):

Nidhya N. Joghee ◽

Gurunathan Jayaraman ◽

Masilamani Selladurai

Keyword(s):

Enzyme Activity ◽

Amino Acid ◽

Thermodynamic Stability ◽

Protective Effects ◽

Residual Enzyme Activity ◽

Functional Stability ◽

Biotechnological Applications ◽

Optimal Temperature ◽

Acidic Conditions ◽

Cellular Components

Background: Nε-acetyl L-α lysine is an unusual acetylated di-amino acid synthesized and accumulated by certain halophiles under osmotic stress. Osmolytes are generally known to protect proteins and other cellular components under various stress conditions. Objective: The structural and functional stability imparted by Nε-acetyl L-lysine on proteins were unknown and hence was studied and compared to other commonly known bacterial osmolytes - ectoine, proline, glycine betaine, trehalose and sucrose. Methods: Effects of osmolytes on the temperature and pH profiles, pH stability and thermodynamic stability of the model enzyme, α-amylase were analyzed. Results: At physiological pH, all the osmolytes under study increased the optimal temperature for enzyme activity and improved the thermodynamic stability of the enzyme. At acidic conditions (pH 3.0), Nε-acetyl L-α lysine and ectoine improved both the catalytic and thermodynamic stability of the enzyme; it was reflected in the increase in residual enzyme activity after incubation of the enzyme at pH 3.0 for 15 min by 60% and 63.5% and the midpoint temperature of unfolding transition by 11°C and 10°C respectively. Conclusion: Such significant protective effects on both activity and stability of α-amylase imparted by addition of Nε-acetyl L-α lysine and ectoine at acidic conditions make these osmolytes interesting candidates for biotechnological applications.

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Preparation of Organized Mesoporous Silica from Sodium Metasilicate Solutions in Alkaline Medium Using Nonionic Surfactants

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20032019 ◽

2003 ◽

Vol 68 (10) ◽

pp. 2019-2031 ◽

Cited By ~ 1

Author(s):

Markéta Zukalová ◽

Jiří Rathouský ◽

Arnošt Zukal

Keyword(s):

Mesoporous Silica ◽

Ethylene Oxide ◽

Sodium Metasilicate ◽

Spherical Particles ◽

Structure Directing Agent ◽

Inorganic Species ◽

Poly Ethylene Oxide ◽

Acidic Conditions ◽

Poly Ethylene ◽

Hydrolysis Of

A new procedure has been developed, which is based on homogeneous precipitation of organized mesoporous silica from an aqueous solution of sodium metasilicate and a nonionic poly(ethylene oxide) surfactant serving as a structure-directing agent. The decrease in pH, which induces the polycondensation of silica, is achieved by hydrolysis of ethyl acetate. Owing to the complexation of Na+ cations by poly(ethylene oxide) segments, assembling of the mesostructure appears to occur under electrostatic control by the S0Na+I- pathway, where S0 and I- are surfactant and inorganic species, respectively. As the complexation of Na+ cations causes extended conformation of poly(ethylene oxide) segments, the pore size and pore volume of organized mesoporous silica increase in comparison with materials prepared under neutral or acidic conditions. The assembling of particles can be fully separated from their solidification, which results in the formation of highly regular spherical particles of mesoporous silica.

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Proteolysis of caseins and the proteose-peptone fraction of bovine milk

Journal of Dairy Research ◽

10.1017/s0022029900023116 ◽

1983 ◽

Vol 50 (3) ◽

pp. 275-290 ◽

Cited By ~ 104

Author(s):

Anthony T. Andrews ◽

Efstathios Alichanidis

Keyword(s):

Gel Electrophoresis ◽

Whey Proteins ◽

Bovine Milk ◽

Major Product ◽

Natural Course ◽

Pasteurized Milk ◽

Proteose Peptone ◽

History Of

SummaryThe proteolysis of highly purified samples of αs1-, αs2-, β-and κ-caseins by porcine plasmin and by bovine plasminogen with urokinase has been examined principally by gel electrophoresis. The resulting peptide band patterns were compared with those of total proteose-peptone (TPP) samples prepared from fresh and stored raw and pasteurized milk, and also with those obtained during the natural course of proteolysis by indigenous enzymes in milk during storage. TPP was found to contain at least 38 components detectable by a single electrophoresis run. Apart from residual traces of whey proteins and intact caseins nearly all of these components were fragments of caseins produced by indigenous plasmin, with products from the breakdown of αs1- and β-casein predominating. Over 90 % of TPP has been accounted for in this way. A fragment consisting of residues 29–105 of β-casein was isolated and characterized from both stored milk and from plasmin digests of β-casein. This fragment was a relatively major product of the natural proteolysis occurring during storage of milk, but contrary to a report in the literature it was not the same as proteose-peptone component 8-slow. Since many of the components of TPP resulted from proteolysis, the composition of TPP was found to vary according to the time and temperature of storage of the milk from which it was prepared. Thus, while the proteose-peptone fraction of milk can easily be defined operationally it cannot be rigorously defined in terms of its composition unless the history of the milk is also defined.

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The Hsp60 Protein of Helicobacter Pylori Exhibits Chaperone and ATPase Activities at Elevated Temperatures

BioChem ◽

10.3390/biochem1010002 ◽

2021 ◽

Vol 1 (1) ◽

pp. 19-25

Author(s):

Jose A. Mendoza ◽

Julian L. Ignacio ◽

Christopher M. Buckley

Keyword(s):

Helicobacter Pylori ◽

Heat Stress ◽

Molecular Chaperone ◽

Elevated Temperatures ◽

Citrate Synthase ◽

Gastric Epithelium ◽

Acidic Conditions ◽

H Pylori ◽

Induced Aggregation ◽

Hydrolysis Of

The heat-shock protein, Hsp60, is one of the most abundant proteins in Helicobacter pylori. Given its sequence homology to the Escherichia coli Hsp60 or GroEL, Hsp60 from H. pylori would be expected to function as a molecular chaperone in this organism. H. pylori is a type of bacteria that grows on the gastric epithelium, where the pH can fluctuate between neutral and 4.5, and the intracellular pH can be as low as 5.0. We previously showed that Hsp60 functions as a chaperone under acidic conditions. However, no reports have been made on the ability of Hsp60 to function as a molecular chaperone under other stressful conditions, such as heat stress or elevated temperatures. We report here that Hsp60 could suppress the heat-induced aggregation of the enzymes rhodanese, malate dehydrogenase, citrate synthase, and lactate dehydrogenase. Moreover, Hsp60 was found to have a potassium and magnesium-dependent ATPase activity that was stimulated at elevated temperatures. Although, Hsp60 was found to bind GTP, the hydrolysis of this nucleotide could not be observed. Our results show that Hsp60 from H. pylori can function as a molecular chaperone under conditions of heat stress.

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