The influence of milk composition on pH and calcium activity measured in situ during heat treatment of reconstituted skim milk

2010 ◽  
Vol 77 (3) ◽  
pp. 257-264 ◽  
Author(s):  
Jayani Chandrapala ◽  
Ian McKinnon ◽  
Mary Ann Augustin ◽  
Punsandani Udabage
Keyword(s):  
Heat Treatment ◽  
High Temperatures ◽  
Skim Milk ◽  
Milk Composition ◽  
Complexing Agents ◽  
Calcium Activity ◽  
Initial Ph ◽  
Ph Decrease ◽  
Milk Solids

The pH and calcium activity of reconstituted skim milk solutions (9–21% w/w milk solids non-fat) on heating and after cooling were studied as a function of milk pH prior to heating (pH 6·2–7·2 at 25°C) and added calcium complexing agents (phosphate or EDTA). The pH decreased as the temperature was raised from 25 to 90°C and the magnitude of the pH decrease was greater with increase in initial pH at 25°C before heating or milk concentration. The pH decrease on heating from 25 to 90°C in skim milk solutions with added calcium complexing agents was lower than that of milk without the addition of these salts. The calcium activity decreased on heating from 25 to 60°C. The magnitude of the change decreased with increase in initial pH at 25°C before heating and milk concentration. The decrease in calcium activity on heating from 25 to 60°C for skim milk solutions with added calcium complexing agents was lower than that of milk solutions without the addition of calcium complexing agents. The changes in pH and calcium activity on heating milk were largely reversible after cooling the milk. The results suggested that the pH and calcium activity at high temperatures are a function of the milk composition. Knowledge of the initial pH prior to heating alone is not sufficient for predicting the changes that occur during heating.

scholarly journals Changes of pH inβ-Lactoglobulin andβ-Casein Solutions during High Pressure Treatment

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Karsten Olsen ◽  
Bo B. Jespersen ◽  
Vibeke Orlien
Keyword(s):  
Tertiary Structure ◽  
Additive Model ◽  
Pressure Treatment ◽  
Ph Change ◽  
Pressure Dependency ◽  
Casein Solution ◽  
Initial Decrease ◽  
Initial Ph ◽  
Ph Decrease

The pH changes in the milk systems,β-lactoglobulin B,β-casein, and mixture ofβ-lactoglobulin andβ-casein (pH 7 and ionic strength 0.08 M) were measuredin situduring increasing pressure up to 500 MPa. An initial decrease to pH 6.7 was observed from 0.1 to 150 MPa forβ-lactoglobulin, followed by an increase to pH 7.3 at 500 MPa. The initial decrease is suggested to be caused by the deprotonation of histidine, while the increase is suggested to result from an increase of hydroxide ions due to the loss of tertiary structure. The change in pH of theβ-casein solution displayed an almost linear increasing pressure dependency up to a pH of 7.7 at 500 MPa. The limited tertiary structure ofβ-casein could allow exposure of all amino acids; thus the increase of pH can be caused by binding of water protons resulting in an increase of hydroxide ions. Addition ofβ-casein toβ-lactoglobulin (1:1) was found to suppress the initial pH decrease found for theβ-lactoglobulin solution. The pH change of the mixture did not suggest any intermolecular interaction, and a simple additive model is proposed to calculate the pH change of the mixture from the corresponding individual samples.

scholarly journals Studies of the Suitability of Preparations of Ewe and Oow Milk for Storing Ram Spermatozoa at 37, 5, and ?79°0

1969 ◽  
Vol 22 (4) ◽  
pp. 983 ◽  
Author(s):  
RC Jones
Keyword(s):  
Heat Treatment ◽  
Protective Action ◽  
Skim Milk ◽  
Optimum Concentration ◽  
Cow Milk ◽  
Toxic Factor ◽  
Cysteine Hydrochloride ◽  
Milk Solids ◽  
Better Than

Ram semen was diluted in skim ewe or cow milk, and in preparations of the non-dialysable components of these resuspended in various synthetic diluents, and was then stored at 37, 5, or -79�C. There was little difference in the protective action of preparations from these two sources. The toxicity of fresh skim milk was reduced by heating at 92�C for 10 min, by the addition of 0�5 mg/ml of cysteine hydrochloride, or by the processes involved in dialysis and lyophilization of the milk solids. However, heat denatured the ewe milk more than the cow milk. The best method of preparing diluents from fresh skim milk was to add 0�5 mg/ml cysteine hydrochloride and then to heat. To remove the toxic factor in fresh cow milk, either heating or addition of cysteine was as effective as, or better than, a combination of both treatments. In the range 0�38-3�00% w/v, the optimum concentration of lyophilized, non-dialysable skim milk preparations added to synthetic diluents depended on their source (i.e. ewe or cow milk), the heat treatment before dialysis, and the measure of response.

Heat-induced changes in the properties of modified skim milks with different casein to whey protein ratios

2014 ◽  
Vol 82 (2) ◽  
pp. 135-142 ◽  
Author(s):  
Mandeep Jeswan Singh ◽  
Jayani Chandrapala ◽  
Punsandani Udabage ◽  
Ian McKinnon ◽  
Mary Ann Augustin
Keyword(s):  
Whey Protein ◽  
Mineral Composition ◽  
Total Protein ◽  
Total Protein Content ◽  
Protein Ratio ◽  
Calcium Activity ◽  
Solids Concentration ◽  
Initial Ph ◽  
Ph Decrease ◽  
Induced Changes

The heat-induced changes in pH, Ca activity and viscosity after heating at 90 °C for 10 min of five modified skim milks were studied as a function of the initial pH of the milks at 25 °C. The milks had (i) different ratios of casein : whey protein (0·03, 1·74, 3·97, 5·27 and 7·25), (ii) the same total solids concentration (9% w/w) and (iii) prior to the adjustment of the pH, similar values of pH (6·67–6·74), concentration of serum calcium, and calcium activity, suggesting that the sera have similar mineral composition. The total protein concentrations of the milks differ (2·8–4·0%, w/w). The pH decrease in situ upon heating from 25–90 °C was similar for all the modified skim milks with the same starting pH, suggesting that the pH changes to milk on heating were primarily mediated by the initial mineral composition of the serum and were unaffected by the casein : whey protein ratio or the total protein content of the milk. The heat-induced changes in pH and calcium activity were largely reversible on cooling. The two milks with the lowest ratios of casein to whey protein gelled on heating to 90 °C for 10 min and cooling to 25 °C when the pH was adjusted to pH = 6·2 prior to heating. The viscosities of all other milks with casein to whey protein ratio of 3·97, 5·27 and 7·25 and/or pH ≥6·7 prior to heating did not change significantly. The effect of casein : whey protein ratio and the pH are the dominant factors in controlling the susceptibility to thickening of the milks on heating in this study.

Eddy Current at High Temperatures for in-Situ Control of Heat Treatment Precipitation in Hardening Aluminum Alloys

2020 ◽  
Vol 20 (23) ◽  
pp. 14514-14520
Author(s):  
Daniel Diehl ◽  
Carlos Kohler ◽  
Eduardo Luis Schneider ◽  
Thomas Gabriel Rosauro Clarke
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloys ◽  
High Temperatures ◽  
Eddy Current ◽  
In Situ Control

QUALITY OF PROTEIN IN MILK REPLACERS FOR YOUNG CALVES. I. FACTORS AFFECTING IN VITRO CURD FORMATION BY RENNET (CHYMOSIN, RENNIN) FROM RECONSTITUTED SKIM MILK POWDER

1976 ◽  
Vol 56 (2) ◽  
pp. 317-325 ◽  
Author(s):  
D. B. EMMONS ◽  
E. E. LISTER
Keyword(s):  
Heat Treatment ◽  
Milk Powder ◽  
Skim Milk ◽  
High Heat ◽  
Skim Milk Powder ◽  
Factors Affecting ◽  
Fresh Milk ◽  
Milk Solids ◽  
Milk Replacers

Fresh milk coagulates with chymosin (rennin) in the calf stomach to form relatively strong curds. With respect to calf milk replacers it is of interest to study factors affecting curd formation of reconstituted skim milk powder by this enzyme. Curd firmness was increased by lower pH of the skim milk over a range of 5.6–6.6, higher concentration of skim milk solids over a range of 5–20%, higher concentrations of chymosin, lower temperatures of heat treatment of skim milk prior to spray drying, and higher temperature of coagulation, 37 vs. 30 C. Reconstitution of powder in water above 56 C for 2 min remarkedly reduced the firmness of the curd. The following coagulation conditions were selected for comparison of powders and milk replacers: addition of 1 ml of a 1:50 dilution of standard strength commercial rennet to 100 ml of milk previously adjusted to pH 6.1, 10% of nonfat solids in the aqueous nonfat phase, temperature of 37 C, and measurements of firmness 30 min after adding rennet. Commercially produced skim milk powders designated high-heat, medium-heat and roller products yielded soft curds. Commercial low-heat powders yielded strong curds. All coagulated in less than 4 min at pH 6.1, the time being relatively independent of heat treatment.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

In situ synthesis of Mn3O4/graphene nanocomposite and its application as a lubrication additive at high temperatures

2021 ◽  
Vol 546 ◽  
pp. 149019
Author(s):  
Bao Jin ◽  
Jun Zhao ◽  
Guangyan Chen ◽  
Yongyong He ◽  
Yiyao Huang ◽  
...  
Keyword(s):  
High Temperatures ◽  
In Situ Synthesis ◽  
Graphene Nanocomposite ◽  
Lubrication Additive

Mechanical Properties of Pyrolytic "SiOCN" Thin Coatings

1993 ◽  
Vol 308 ◽  
Author(s):  
Sandrine Bec ◽  
André Tonck ◽  
Jean-Luc Loubet
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Ceramic Coatings ◽  
Optical Observation ◽  
Thin Coatings ◽  
Polymer Precursors ◽  
Polymeric State

ABSTRACTPyrolysis of polymer precursors (polysilazane) is a technologically and economically interesting way to produce thin ceramic coatings. However, many cracks appear and decohesion occurs during pyrolysis when the ceramic coatings (SiOCN) are thicker than 0.5 micrometers. In order to understand these cracking phenomena, the coatings are mechanically characterized by nanoindentation at different stages of the pyrolysis heat treatment.During pyrolysis, the cracking temperature is detected by in-situ optical observation. The thickness of the coatings varies during pyrolysis from 3 micrometers at the polymeric state to 1 micrometer at the ceramic state. The coatings' properties, hardness and Young's modulus are evaluated after heat treatment, taking into account the substrate's influence. A large variation of these properties occurs at the cracking temperature. Both the hardness and the Young's modulus are multiplied by a factor of 10. By analysing these results, we show that cracking is correlated with the evolution of the coatings' mechanical properties during the transformation.

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