Effect of Calcium, N-Ethylmaleimide and Casein upon Heat-Induced Whey Protein Aggregation

Morr, C.V.; Josephson, R.V.

doi:10.3168/jds.s0022-0302(68)87193-0

Cited by 72 publications

(27 citation statements)

References 13 publications

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“…It has been shown that calcium enhances the extent of protein-protein interactions that may occur during heating of milk [5,14,21]. However, our results indicate that the protein fraction that is recovered in whey from thermally treated milks is not subjected to pH-dependent, Ca 2+ -mediated, insolubilization.…”

Section: Resultscontrasting

confidence: 53%

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Composition and calcium status of acid whey from pasteurized, UHT-treated and in-bottle sterilized milks

Carbonaro

Lucarini

Lullo

2000

Nahrung

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Whey extracts were obtained from pasteurized, UHT-treated and in-bottle sterilized milks. After acidic precipitation of casein the concentration of protein, NPN, lactose, lipid, calcium, magnesium and potassium was determined. Among the parameters examined, protein content was significantly reduced in the whey extracts from UHT-treated and in-bottle sterilized milks compared with that from pasteurized milk, while lactose content was increased. Calcium extracted in whey was at least 80% of total calcium of the milk. The total calcium to protein ratio of whey was increased as a function of the thermal treatment of milk, while ionic calcium was about 50% of total calcium in all whey extracts. In vitro protein digestibility was found to be significantly lower in whey from UHT-treated and in-bottle sterilized milks than in that from pasteurized milk. Parallel estimation of the percentage of ionic calcium and of the solubility of proteins in the pH range 2-10 indicated that calcium was not involved in the pH-dependent solubility of proteins extracted in the whey, the extent of solubility being essentially a function of the thermal treatment of milk. The results suggest that calcium was not responsible for the formation of soluble protein macroaggregates with impaired digestibility that are present in whey from milk subjected to heat treatment of increasing intensity.

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Section: Resultscontrasting

confidence: 53%

“…It has been suggested that calcium is involved in the final steps of the aggregation process where large aggregates are formed [14].…”

Section: Introductionmentioning

confidence: 99%

Composition and calcium status of acid whey from pasteurized, UHT-treated and in-bottle sterilized milks

Carbonaro

Lucarini

Lullo

2000

Nahrung

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“…Our results show that ␣ s -casein not only prevents the aggregation of unrelated proteins but also protects its natural substrates in vivo against thermal aggregation. Early work by Morr and co-workers (30,31) also clearly demonstrated that whole casein prevented gross heat-induced aggregation of whey proteins through nonspecific interaction, even in calcium-containing systems.…”

Section: Resultsmentioning

confidence: 99%

Molecular Chaperone-like Properties of an Unfolded Protein, αs-Casein

Bhattacharyya¹,

Das

1999

Journal of Biological Chemistry

181

159

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All molecular chaperones known to date are well organized, folded protein molecules whose three-dimensional structure are believed to play a key role in the mechanism of substrate recognition and subsequent assistance to folding. A common feature of all protein and nonprotein molecular chaperones is the propensity to form aggregates very similar to the micellar aggregates. In this paper we show that ␣ s -casein, abundant in mammalian milk, which has no well defined secondary and tertiary structure but exits in nature as a micellar aggregate, can prevent a variety of unrelated proteins/ enzymes against thermal-, chemical-, or light-induced aggregation. It also prevents aggregation of its natural substrates, the whey proteins. ␣ s -Casein interacts with partially unfolded proteins through its solvent-exposed hydrophobic surfaces. The absence of disulfide bridge or free thiol groups in its sequence plays important role in preventing thermal aggregation of whey proteins caused by thiol-disulfide interchange reactions. Our results indicate that ␣ s -casein not only prevents the formation of huge insoluble aggregates but it can also inhibit accumulation of soluble aggregates of appreciable size. Unlike other molecular chaperones, this protein can solubilize hydrophobically aggregated proteins. This protein seems to have some characteristics of cold shock protein, and its chaperone-like activity increases with decrease of temperature.

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“…Similarly, Kulozik (2008) demonstrated that the size and the internal structure of the whey protein aggregates depend on temperature and composition, such as lactose content. For Morr and Josephson (1968), due to denaturation, whey proteins formed primary aggregates of about 200 kDa, the growth of which depended on salt ions. For Li-Chan (1983), the greatest impairment of protein solubility and the greatest loss of reactive -SH groups was reported at pH higher than 7 after heating at temperatures above 80°C because of the prevailing protein-protein interactions; in this case, disulfide and hydrophobic bonding were mainly responsible for the heat-induced formation of insoluble aggregates.…”

Section: Introductionmentioning

confidence: 99%