Ethanol stability of casein micelles – a hypothesis concerning the role of calcium phosphate

1987 ◽  
Vol 54 (3) ◽  
pp. 389-395 ◽  
Author(s):  
David S. Horne
Keyword(s):  
Ionic Strength ◽  
Skim Milk ◽  
Buffer System ◽  
Casein Micelles ◽  
Buffer Solutions ◽  
Relative Response ◽  
Using Data ◽  
The Stability ◽  
Ethanol Stability

SummaryThe ethanol (EtOH) stability of skim milk and the stability towards aggregation of casein micelles diluted into ethanolic buffer solutions were compared using data obtained from previously published experiments. Differences in absolute stability and in relative response were observed when Ca2+ level and pH were adjusted, the buffer system results lying below those from skim milk in both cases. Increasing the ionic strength of skim milk adjusted to pH 7·0 lowered its EtOH stability whereas increasing the ionic strength of the diluting buffer increased the stability of the casein micelles. The hypothesis is put forward that the differences are due to the simultaneous precipitation of Ca phosphate when EtOH is added to skim milk. This draws calcium from the caseinate sites of the micelle, counteracting the destabilizing effects of the EtOH towards the micelle. Such removal and the consequent restructuring are kinetically controlled and micellar precipitation in skim milk finally occurs when the micellar coagulation time falls within the time scale of the restructuring reactions.

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.

scholarly journals The Role of Employment Protection during an Exogenous Shock to an Economy

2011 ◽  
Vol 11 (2) ◽  
pp. 1850225 ◽  
Author(s):  
Miki Malul ◽  
Mosi Rosenboim ◽  
Tal Shavit ◽  
Shlomo Yedidia Tarba
Keyword(s):  
Economic Crisis ◽  
Employment Protection ◽  
Exogenous Shock ◽  
Unemployment Rates ◽  
World Crisis ◽  
Automatic Stabilizer ◽  
Medium Level ◽  
Using Data ◽  
The Stability

This paper explores the role of employment protection when powerful external crises reduce demand for products. We first present a theoretical framework that shows that employment protection has a U-shaped effect on abnormal unemployment during a negative exogenous shock to an economy. Using data from the 33 OECD countries, we analyze how the level of employment protection affected the stability of unemployment rates during the recent global economic crisis. The results suggest that countries with an intermediate level of employment protection will have more stable unemployment rates during a world crisis. The policy implication of our paper is that countries should seek a medium level of employment protection that may act as an automatic stabilizer of the economy on the macro level.

Stability of buffalo casein micelles

1979 ◽  
Vol 46 (2) ◽  
pp. 401-405 ◽  
Author(s):  
Nripendra C. Ganguli
Keyword(s):  
Sialic Acid ◽  
Gel Filtration ◽  
Skim Milk ◽  
Heat Stability ◽  
Casein Micelles ◽  
Heat Stable ◽  
Micellar Casein ◽  
Acid Release ◽  
The Stability ◽  
Better Than

SUMMARYBuffalo skim-milk is less heat stable than cow skim-milk. Interchanging ultracentrifugal whey (UCW) and milk diffusate with micellar casein caused significant changes in the heat stability of buffalo casein micelles (BCM) and cow casein micelles (CCM). Buffalo UCW dramatically destabilized COM, whereas buffalo diffu-sate with CCM exhibited the highest heat stability.Cow κ-casein stabilizes αs-casein against precipitation by Ca better than buffalo º-casein. About 90% of αs-casein could be stabilized by κ: αs ratios of 0·20 and 0·231 for cow and buffalo, respectively.Sialic acid release from micellar κ-casein by rennet was higher than from acid κ-casein in both buffalo and cow caseins, the release being slower in buffalo. The released macropeptide from buffalo κ-casein was smaller than that from cow κ-casein as revealed by Sephadex gel filtration.Sub-units of BCM have less sialic acid (1·57mg/g) than whole micelles (2·70mg/g). On rennet action, 47% of bound sialic acid was released from sub-units as against 85% from whole micelles. The sub-micelles are less heat stable than whole micelles. Among ions tested, added Ca reduced heat stability more dramatically in whole micelles, whereas added phosphate improved the stability of micelles and, more strikingly, of sub-micelles. Citrate also improved the heat stability of sub-micelles but not of whole micelles.

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.

Trophic structure within the Bristol Channel: seasonality and stability in Bridgwater Bay

1992 ◽  
Vol 72 (3) ◽  
pp. 675-690 ◽  
Author(s):  
P. A. Henderson ◽  
D. James ◽  
R. H. A. Holmes
Keyword(s):  
Trophic Structure ◽  
General Description ◽  
Dominant Animal ◽  
Estuarine Site ◽  
Overall Stability ◽  
Average Biomass ◽  
Using Data ◽  
The Stability ◽  
Stability And Resilience

A general description of the trophic inter-relationships and the food web within Bridgwater Bay, Somerset, England, is presented. This Bay is a lower estuarine site within the Bristol Channel. Particular attention is given to the use of the area by fish and larger crustaceans which are the dominant animal groups. Using data collected over a ten-year period of monthly sampling, the relative average biomass of all fish and larger crustaceans found within the Bay is calculated for each month of the year. These averages are used to produce food webs which also show species relative abundance for each calendar month.It is shown that the trophic structure follows a seasonal cycle due to migration. The application of the concept of stability within such a dynamic system is discussed. The role of compartmentalization of the ecosystem into a number of loosely connected groups as an aid to overall stability is discussed. While there is no evidence that contemporaneous compartments exist, it is argued that inter-specific interactions are temporally limited because of the different periods of annual residence of the species. It is suggested that the stability and resilience to interference shown by these estuarine systems is enhanced by temporal partitions.

The role of divalent cations in the activation of the NADP+-specific isocitrate dehydrogenase from Pisum sativum L.

1977 ◽  
Vol 55 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Robert J. Maloney ◽  
David T. Dennis
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Isocitrate Dehydrogenase ◽  
Divalent Cations ◽  
Free Form ◽  
Saturation Kinetics ◽  
The Difference ◽  
The Stability ◽  
Kinetics Of

A divalent cation electrode was used to measure the stability constants (association constants) for the magnesium and manganese complexes of the substrates for the NADP+-specific isocitrate dehydrogenase (EC 1.1.1.42) from pea stems. At an ionic strength of 26.5 mM and at pH 7.4 the stability constants for the Mg2+–isocitrate and Mg2+–NADP+ complexes were 0.85 ± 0.2 and 0.43 ± 0.04 mM−1 respectively and for the Mn2+–isocitrate and Mn2+–NADP+ complexes they were 1.25 ± 0.07 and 0.75 ± 0.09 mM−1 respectively. At the same ionic strength but at pH 6.0 the Mg2+–NADPH and Mn2+–NADPH complexes had stability constants of 0.95 ± 0.23 and 1.79 ± 0.34 mM−1 respectively. Oxalosuccinate and α-ketoglutarate do not form measureable complexes under these conditions. Saturation kinetics of the enzyme with respect to isocitrate and metal ions are consistent with the metal–isocitrate complex being the substrate for the enzyme. NADP+ binds to the enzyme in the free form. Saturation kinetics of NADPH and Mn2+ indicate that the metal–NADPH complex is the substrate in the reverse reaction. In contrast the pig heart enzyme appears to bind free NADPH and Mn2+. A scheme for the reaction mechanism is presented and the difference between the reversibility of the NAD+ and NADP+ enzyme is discussed in relation to the stability of the NADH and NADPH metal complexes.

scholarly journals PERAN BAITUL MAAL WAT TAMWIL (BMT) AMANAH UMMAH TERHADAP PENINGKATAN USAHA PEDAGANG KECIL DI PASAR KARAH SURABAYA

2019 ◽  
Vol 5 (2) ◽  
pp. 93
Author(s):  
Puspa Indraswari ◽  
Qudsi Fauzi
Keyword(s):  
Data Collection ◽  
Research Methods ◽  
Direct Observation ◽  
Qualitative Method ◽  
Business Income ◽  
Using Data ◽  
The Stability ◽  
Small Traders

This study aims to analyze the role of BMT “Amanah Ummah” in empower the small traders. The research methods used in this research was case study qualitative method, using data collection techniques performed with conductive interviews and direct observation with the object of research. The result of this study indicate that BMT has been instrumental in increasing the business of small traders in Karah market. The business improvement from the small traders can be seen from the business turnover, business asset, business income and the stability of their business. The member of BMT in Karah market, on average has increased their business seen from their business volume, increasing of daily inventory such asequipment used for trade and revenues of their business income.

Influence of aggregation on the susceptibility of casein to proteolysis

1970 ◽  
Vol 37 (2) ◽  
pp. 173-180 ◽  
Author(s):  
P. F. Fox
Keyword(s):  
Calcium Phosphate ◽  
Equilibrium Dialysis ◽  
Limited Proteolysis ◽  
Skim Milk ◽  
Sodium Caseinate ◽  
Casein Micelle ◽  
Casein Micelles ◽  
Micelle Structure ◽  
Colloidal Calcium Phosphate

SummaryThe susceptibility of the casein in milk to proteolysis was shown to be greatly influenced by its state of aggregation. In normal milk, where the casein is largely in micellar form, the αs1- and β-caseins are almost inaccessible to proteolysis. On removal of the colloidal phosphate, the casein micelles disintegrate, rendering the components, especially the αs1-casein, accessible to proteolysis. The role of colloidal calcium phosphate in the casein micelle is believed to be that of a non-specific aggregating agent which can be effectively replaced by calcium. Dissolved colloidal phosphate can be effectively reformed by elevation of the pH of colloidal phosphate-free (CPF) milk before equilibrium dialysis. Addition of κ-casein to CPF milk also causes aggregation of the component caseins but the micelles formed are smaller than those of normal milk.The behaviour of micellar β-casein differs considerably from that of micellar αs1-casein. The evidence suggests that part of the β-casein freely dissociates either outside or within the micelle when the temperature is reduced. The temperature dependence of the susceptibility of β-casein to proteolysis was similar in skim-milk and in solutions of sodium caseinate, and increased as the temperature was reduced. αs1-Casein was quite resistant to proteolysis in normal milk but became susceptible when the micelle structure was disrupted on removal of colloidal phosphate.It is concluded that limited proteolysis may prove a valuable technique in the study of casein micelle structure.

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.

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