scholarly journals A calorimetric study of the thermal denaturation of whey proteins in simulated milk ultrafiltrate

1977 ◽  
Vol 44 (3) ◽  
pp. 509-520 ◽  
Author(s):  
M. Rüegg ◽  
Ursula Moor ◽  
B. Blanc
Keyword(s):  
Heat Treatment ◽  
Xanthine Oxidase ◽  
Conformational Changes ◽  
Thermal Denaturation ◽  
Whey Proteins ◽  
Calorimetric Study ◽  
Thermal Transitions ◽  
Scanning Calorimetry ◽  
Β Lactoglobulin ◽  
Dsc Thermograms

SummaryDifferential scanning calorimetry (DSC) was used to study thermal transitions of the following whey proteins and enzymes in milk ultrafiltrate solution: β-lactoglobulin, α-lactalbumin, serum albumin, γ-globulin, apo- and Fe-lactoferrin, lysozyme, ribonuclease, α-chymotrypsin and xanthine oxidase. Denaturation enthalpies (ΔHD), denaturation temperatures (TD) and the half width of the denaturation peaks in DSC thermograms (ΔT½D) were determined and the degree of renaturation was estimated by rescanning previously denatured samples. A fair correlation between the results obtained by DSC and other more classical methods was found in general. However, for some proteins (α-lactalbumin, lysozyme, ribonuclease and xanthine oxidase), which have so far been considered relatively thermostable, calorimetry reveals conformational changes starting at temperatures as low as about 45 °C. In these cases thermostability observed after heat treatment of milk should be interpreted in terms of renaturation and not of high temperatures of denaturation.

A differential scanning calorimetric study of the thermal behaviour of bovine β-lactoglobulin at temperatures up to 160 °C

1981 ◽  
Vol 48 (2) ◽  
pp. 293-302 ◽  
Author(s):  
Jacob N. de Wit ◽  
Gijsbert Klarenbeek
Keyword(s):  
Thermal Behaviour ◽  
Conformational Changes ◽  
Temperature Shift ◽  
Differential Scanning Calorimetric ◽  
Calorimetric Study ◽  
Scanning Calorimetry ◽  
Maximum Heat ◽  
Β Lactoglobulin ◽  
Endothermal Peak ◽  
Dsc Curves

SummaryThe thermal behaviour of β-lactoglobulin was studied by differential scanning calorimetry (DSC) in the temperature range 40–160 °C. The DSC curves revealed, in addition to the usually observed denaturation peak near 80 °C, a distinct endothermal peak between 130 and 150 °C. When the pH was increased from 6·5, the area under the peak near 80 °C (denaturation heat) decreased significantly, whereas the peak area near 140 °C increased. The temperature of maximum heat absorption in the peaks near both 80 and 140 °C gradually increased as the pH decreased. Addition of sugars and variation of the heating rate both caused a temperature shift of the endothermal heat effect at 140 °C, similar to that at 80 °C. No peak near 140 °C was observed when β-mercapto-ethanol was added to the β-lactoglobulin solution before scanning. The origin and nature of the high temperature denaturation peak is discussed in terms of conformational changes of the protein.

Assessment of the Thermal Treatment of Milk during Continuous Microwave and Conventional Heating

1996 ◽  
Vol 59 (8) ◽  
pp. 889-892 ◽  
Author(s):  
ROSINA LOPEZ-FANDIÑO ◽  
MAR VILLAMIEL ◽  
NIEVES CORZO ◽  
AGUSTIN OLANO
Keyword(s):  
Heat Treatment ◽  
Continuous Flow ◽  
Thermal Denaturation ◽  
Microwave Treatment ◽  
Conventional Heating ◽  
Treatment Intensity ◽  
Heat Distribution ◽  
Conventional System ◽  
Effective System ◽  
Β Lactoglobulin

The effect of continuous-flow microwave treatment of milk was estimated by using indicators of the heat treatment intensity (β-lactoglobulin denaturation, inactivation of alkaline phosphatase and lactoperoxidase). Results were compared with those obtained using a conventional process having the same heating, holding, and cooling phases. Continuous microwave treatment proved to be an effective system for pasteurizing milk, with the inclusion of a holding phase to maintain the time and temperature conditions required. At high pasteurization temperatures, the extent of thermal denaturation observed with the microwave treatment was lower than that obtained with the conventional system. This result could be attributed to a better heat distribution and the lack of hot surfaces contacting the milk in the case of the microwave unit.

scholarly journals Optical backscatter method for determining thermal denaturation of β-lactoglobulin and other whey proteins in milk

2013 ◽  
Vol 96 (3) ◽  
pp. 1356-1365 ◽  
Author(s):  
Alisa Lamb ◽  
Fred Payne ◽  
Youling L. Xiong ◽  
Manuel Castillo
Keyword(s):  
Thermal Denaturation ◽  
Whey Proteins ◽  
Β Lactoglobulin

scholarly journals A calorimetric study of human CuZn superoxide dismutase

1987 ◽  
Vol 248 (3) ◽  
pp. 981-984 ◽  
Author(s):  
C G Biliaderis ◽  
R J Weselake ◽  
A Petkau ◽  
A D Friesen
Keyword(s):  
Differential Scanning Calorimetry ◽  
Binding Sites ◽  
Specific Activity ◽  
Calorimetric Study ◽  
Thermal Transitions ◽  
Scanning Calorimetry ◽  
Structural Units ◽  
Conformational Order ◽  
Higher Temperature ◽  
Cuzn Superoxide Dismutase

Structural alterations, as manifested by thermal transitions, caused by removal or binding of metal ions to human and bovine CuZn superoxide dismutases (SODs) were investigated by differential scanning calorimetry. Although holo forms of the two mammalian enzymes exhibited irreversible thermal transitions (delta Hcal. = 27.7 J/g and Td = 104 degrees C for bovine SOD; delta Hcal. = 23.6 J/g and Td = 101 degrees C for human SOD), only the bovine apoenzyme showed the presence of a less thermostable form (delta Hcal. = 10.7 J/g and Td = 63 degrees C). These observations suggested that human apo-SOD had considerably less conformational order than bovine apo-SOD. Reconstitution of human and bovine apoenzymes with Cu2+ and Zn2+ resulted in recovery of thermodynamic parameters and specific activity. Binding of Zn2+ alone to human apo-SOD resulted in the formation of two distinct structural units, detectable by differential scanning calorimetry, which underwent conformational disorder at 82 and 101 degrees C respectively. Saturation of binding sites with both Zn2+ and Cu2+ appeared to stabilize the enzyme structure further as shown by elimination of the low-temperature transition and the appearance of another thermal transition at a higher temperature.

Heat-induced and other chemical changes in commercial UHT milks

2005 ◽  
Vol 72 (4) ◽  
pp. 442-446 ◽  
Author(s):  
Anthony J Elliott ◽  
Nivedita Datta ◽  
Boka Amenu ◽  
Hilton C Deeth
Keyword(s):  
Heat Treatment ◽  
Bovine Serum Albumin ◽  
Bovine Serum ◽  
Room Temperature ◽  
Whey Proteins ◽  
Thermally Induced ◽  
Heated Milk ◽  
Heat Treated ◽  
Induced Changes ◽  
Β Lactoglobulin

The properties of commercial directly and indirectly heated UHT milks, both after heating and during storage at room temperature for 24 weeks, were studied. Thermally induced changes were examined by changes in lactulose, furosine and acid-soluble whey proteins. The results confirmed previous reports that directly heated UHT milks suffer less heat damage than indirectly heated milk. During storage, furosine increased and bovine serum albumin in directly heat-treated milks decreased significantly. The changes in lactulose, α-lactalbumin and β-lactoglobulin were not statistically significant. The data suggest that heat treatment indicators should be measured as soon as possible after processing to avoid any misinterpretations of the intensity of the heat treatment.

A calorimetric study of the thermal transitions of Halobacterium cutirubrum

1982 ◽  
Vol 60 (4) ◽  
pp. 419-421 ◽  
Author(s):  
K. C. Cho ◽  
K. C. Chow ◽  
K. K. Mark
Keyword(s):  
Differential Scanning Calorimetry ◽  
Envelope Glycoprotein ◽  
Hydrophobic Interactions ◽  
Major Protein ◽  
Calorimetric Study ◽  
Thermal Transitions ◽  
Scanning Calorimetry ◽  
Previous Proposal ◽  
Protein Components

The thermal transitions of Halobacterium cutirubrum have been examined by differential scanning calorimetry. Two distinct peaks corresponding to the denaturation of two major protein components were observed in the heating curves. One of the peaks has been assigned to the denaturation of the envelope glycoprotein. The variations of the denaturation temperatures with the addition of glucose, glycerol, NaNO3, and NaSCN are consistent with the previous proposal that hydrophobic interactions are essential in stabilizing the glycoprotein.

scholarly journals Calorimetric Study of Helix aspersa Maxima Hemocyanin Isoforms

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Svetla Todinova ◽  
Yuliana Raynova ◽  
Krassimira Idakieva
Keyword(s):  
Thermal Denaturation ◽  
Irreversible Process ◽  
Arrhenius Equation ◽  
Helix Aspersa ◽  
Thermal Unfolding ◽  
Calorimetric Study ◽  
Scanning Calorimetry ◽  
Scan Rate ◽  
Annealing Procedure ◽  
Helix Aspersa Maxima

The thermal unfolding of hemocyanin isoforms, β-HaH and αD+N-HaH, isolated from the hemolymph of garden snails Helix aspersa maxima, was studied by means of differential scanning calorimetry (DSC). One transition, with an apparent transition temperature (Tm) at 79.88°C, was detected in the thermogram of β-HaH in 20 mM HEPES buffer, containing 0.1 M NaCl, 5 mM CaCl2, and 5 mM MgCl2, pH 7.0, at scan rate of 1.0°C min−1. By means of successive annealing procedure, two individual transitions were identified in the thermogram of αD+N-HaH. Denaturation of both hemocyanins was found to be an irreversible process. The scan-rate dependence of the calorimetric profiles indicated that the thermal unfolding of investigated hemocyanins was kinetically controlled. The thermal denaturation of the isoforms β-HaH and αD+N-HaH was described by the two-state irreversible model, and parameters of the Arrhenius equation were calculated.

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