The Relations of Hydrogen-Ion Concentration to the Heat Coagulation of Proteins in Swiss Cheese Whey.

Okuda, Yuzuru; Zöller, Harper F.

doi:10.1021/ie50138a008

Cited by 7 publications

(3 citation statements)

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“…Heat-induced denaturation of proteins has been extensively studied. − For whey proteins, such as β-lactoglobulin, denaturation was described to lead to decreased solubility at pH 4.6 ,− (i.e., close to the isoelectric point of the protein). The extent of precipitation of whey proteins at pH 4.6 has, in time, evolved into a standard protocol to quantify the proportion of “native” and denatured proteins in heated solutions. , Using this method, it was found that the amount of native-like β-lactoglobulin (β-lg) decreased slowly during heating, even at relatively high temperatures.…”

Section: Introductionmentioning

confidence: 99%

Controlling the Ratio between Native-Like, Non-Native-Like, and Aggregated β-Lactoglobulin after Heat Treatment

Delahaije

Gruppen

Boxtel

et al. 2016

J. Agric. Food Chem.

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The amount of heat-denatured whey protein is typically determined by pH 4.6 precipitation. Using this method, a significant amount of nondenatured protein was reported even after long heating times. Apparently, a fraction of the unfolded protein refolds into the "native" state rather than form aggregates. This fact is known and has been explained using kinetic models. How the conditions affect the refolding and aggregation is, however, not fully understood. Therefore, this study investigates the unfolding, refolding, and aggregation process of β-lactoglobulin using circular dichroism and size-exclusion chromatography to characterize different folding variants and to quantify their content. The proteins remaining in solution at pH 4.6 were confirmed to be native-like. The nonaggregated fraction contains proteins with a native-like and two types of nonnative-like conformations. The nonaggregated fraction increased with decreasing temperature (60−90 °C) and concentration (1−50 g/L) and increasing electrostatic repulsion (pH 7−8; 0−50 mM). The native-like fraction in the nonaggregated fraction was independent of pH, ionic strength, and concentration but increased with decreasing temperature.

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Section: Introductionmentioning

confidence: 99%

Controlling the Ratio between Native-Like, Non-Native-Like, and Aggregated β-Lactoglobulin after Heat Treatment

Delahaije

Gruppen

Boxtel

et al. 2016

J. Agric. Food Chem.

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“…In their native form, β-lg and α-la are soluble at all pH values, including at their pI, 5.1 and 4.2-4.5 respectively (Eigel et al, 1984). The denaturation and aggregation of whey proteins causes their precipitation at pH 4.6 (Okuda and Zoller, 1921). This allowed the measurement of the native proteins during heating, by precipitation of the denatured and subsequently aggregated proteins at pH 4.6, and thus, the estimation of a rate of denaturation in the very early stage of heating.…”

Section: Denaturation Of β-Lg and α-La In The Presence Of Cmp And D-cmpmentioning

confidence: 99%

Influence of desialylation of caseinomacropeptide on the denaturation and aggregation of whey proteins

Gaspard

Sunds

Larsen

et al. 2020

Journal of Dairy Science

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The effect of the addition of caseinomacropeptide (CMP) or desialylated-CMP on the heat-induced denaturation and aggregation of whey proteins was investigated in the pH range 3 to 7 after heating at 80°C for 30 min. The rate and temperature of denaturation, the extent of aggregation and the changes in secondary structure of the whey proteins heated in presence of CMP or desialylated-CMP were measured. The sialic acid bound to CMP favored the denaturation and aggregation of the whey proteins when the whey proteins were oppositely charged to CMP at pH 4. A transition occurred at pH 6, below which the removal of sialic acid enhanced the stabilizing properties of the CMP against the denaturation and aggregation of the whey proteins. At pH > 6, the interactions between desialylated-CMP and the whey proteins led to more extensive denaturation and aggregation. Sialic acid bound to CMP influenced the denaturation and aggregation behavior of whey proteins in a pH-dependent manner and this should be considered in future studies on the heat stability of such systems containing CMP.

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“…The maximum amount of casein is precipitated at a yH of 4-5-4-7, a range which covers the isoelectric point of the protein. Heatdenatured albumin and globulin are also precipitated within this range (16), which can best be obtained in milk by a suitable acetic acid-sodium acetate buffer.…”

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confidence: 99%

71. The Heat Denaturation of Albumin and Globulin in Milk

Rowland

1933

Journal of Dairy Research

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IT has been shown by Hardy(i), Chick and Martin(2), Lepeschkin(3), Wu and Wu(4) and Lewis (5), using solutions of egg albumin and oxyhaemoglobin, that heat coagulation consists of two distinct processes: (a) denaturation, or the alteration of the protein under the influence of heat, which must precede (b) flocculation, the rapid separation of the denatured protein in the presence of a suitable electrolyte. The denaturation causes loss of solubility of the protein in water and in dilute salt solutions at its isoelectric point, and is irreversible. The rate of change is influenced by temperature, the concentration of hydrogen or hydroxyl ions, and the neutral salt content. Water is necessary for heat denaturation, but the chemical change in the protein molecules is still obscure. Wichmann(6) and Chick and Martin (2) demonstrated that no change occurs when egg albumin is heated to high temperatures in the dry state.Denaturation and coagulation should not be confused, since coagulation includes the second process of flocculation by neutralisation of the particle charge, and denaturation may take place without being followed by flocculation. Salt-free albumin in solution will not coagulate on boiling, but will be denatured, after which precipitation will occur if a small amount of electrolyte be added. Similarly the term denaturation and not coagulation is applied to the change which takes place in the albumin and globulin when milk is heated. There is no visible coagulation, but the conditions determining the dispersion of the albumin and globulin are changed. The larger associated particles of denatured albumin and globulin are readily precipitated by acid and by salt solutions. The denaturation which takes place on heating milk is made evident, and its extent measured, by the precipitation of albumin and globulin in addition to casein when the heated milk is treated with those reagents which precipitate casein alone from unheated milk.The heat coagulation of isolated pure proteins in solution has been studied extensively, but there is little knowledge of the effects on the lactalbumin and lactoglobulin when milk is heated, and it will readily be seen that the data available are not in agreement. Sebelien(7) observed that an aqueous solution of lactalbumin was coagulated by heating in salt solution at 72° C, while on heating milk itself Orla-Jensen and Plattner (8) found only slight coagulation

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The Relations of Hydrogen-Ion Concentration to the Heat Coagulation of Proteins in Swiss Cheese Whey.

Cited by 7 publications

References 0 publications

Controlling the Ratio between Native-Like, Non-Native-Like, and Aggregated β-Lactoglobulin after Heat Treatment

Controlling the Ratio between Native-Like, Non-Native-Like, and Aggregated β-Lactoglobulin after Heat Treatment

Influence of desialylation of caseinomacropeptide on the denaturation and aggregation of whey proteins

71. The Heat Denaturation of Albumin and Globulin in Milk

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