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SDS-PAGE Analysis of Soluble Proteins in Reconstituted Milk Exposed to Different Heat Treatments

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ABSTRACT

This paper deals with the investigation of the impact of the heat treatment of reconstituted skim milk conducted at different temperatures, and the adding of demineralized whey on the protein solubility, soluble protein composition and interactions involved between proteins in a chemical complex. Commercial skim milk has been reconstituted and heat treated at 75°C, 85°C and 90°C for 20 minutes. Demineralized whey has been added in concentrations of 0.5%, 1.0 and 2.0%. The soluble protein composition has been determined by the polyacrilamide gel electrophoresis (SDS-PAGE) and by the densitometric analysis. Due to the different changes occurred during treatments at different temperatures, proteins of heat-treated samples containing added demineralized whey have had significantly different solubility. At lower temperatures (75°C and 85°C) the adding of demineralized whey decreased the protein solubility by 5.28%-26.41%, while the addition of demineralized whey performed at 90°C increased the soluble protein content by 5.61%-28.89%. Heat treatments, as well as the addition of demineralized whey, have induced high molecular weight complex formation. β-Lg, α-La and κ-casein are involved in high molecular weight complexes. The disulfide interactions between denatured molecules of these proteins are mostly responsible for the formation of coaggregates. The level of their interactions and the soluble protein composition are determined by the degree of temperature.

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The SDS-PAGE pattern of the untreated reconstituted skim milk on 12.5 % gel; 1. 2. Reconstituted skim milk (the sample without and the sample with 2-mercaptoethanol, respectively), 3.α-La, 4. κ-casein, 5, 6. β-Lg, 7. β-casein, 8. Molecular weight standards. The SDS-electrophoretic profile of the soluble skim milk proteins (Fig. 1, line 1) contains five major bands identified as αs- casein, β-casein, α-La, 71 kDa-band, and three minor bands identified as β-Lg, κ-casein and 141 kDa-bands. According to the densitometric analysis (Fig. 2), the five major soluble components represent 83.71% of the soluble protein fraction. Furthermore, the content of the casein fraction and α–La is 69.86% and 6.92%, respectively.
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f1-sensors-07-00371: The SDS-PAGE pattern of the untreated reconstituted skim milk on 12.5 % gel; 1. 2. Reconstituted skim milk (the sample without and the sample with 2-mercaptoethanol, respectively), 3.α-La, 4. κ-casein, 5, 6. β-Lg, 7. β-casein, 8. Molecular weight standards. The SDS-electrophoretic profile of the soluble skim milk proteins (Fig. 1, line 1) contains five major bands identified as αs- casein, β-casein, α-La, 71 kDa-band, and three minor bands identified as β-Lg, κ-casein and 141 kDa-bands. According to the densitometric analysis (Fig. 2), the five major soluble components represent 83.71% of the soluble protein fraction. Furthermore, the content of the casein fraction and α–La is 69.86% and 6.92%, respectively.

Mentions: The SDS-PAGE profile of soluble proteins of the untreated reconstituted skim milk is shown in Fig.1, while densitometric analysis is shown in fig. 2.


SDS-PAGE Analysis of Soluble Proteins in Reconstituted Milk Exposed to Different Heat Treatments
The SDS-PAGE pattern of the untreated reconstituted skim milk on 12.5 % gel; 1. 2. Reconstituted skim milk (the sample without and the sample with 2-mercaptoethanol, respectively), 3.α-La, 4. κ-casein, 5, 6. β-Lg, 7. β-casein, 8. Molecular weight standards. The SDS-electrophoretic profile of the soluble skim milk proteins (Fig. 1, line 1) contains five major bands identified as αs- casein, β-casein, α-La, 71 kDa-band, and three minor bands identified as β-Lg, κ-casein and 141 kDa-bands. According to the densitometric analysis (Fig. 2), the five major soluble components represent 83.71% of the soluble protein fraction. Furthermore, the content of the casein fraction and α–La is 69.86% and 6.92%, respectively.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3756726&req=5

f1-sensors-07-00371: The SDS-PAGE pattern of the untreated reconstituted skim milk on 12.5 % gel; 1. 2. Reconstituted skim milk (the sample without and the sample with 2-mercaptoethanol, respectively), 3.α-La, 4. κ-casein, 5, 6. β-Lg, 7. β-casein, 8. Molecular weight standards. The SDS-electrophoretic profile of the soluble skim milk proteins (Fig. 1, line 1) contains five major bands identified as αs- casein, β-casein, α-La, 71 kDa-band, and three minor bands identified as β-Lg, κ-casein and 141 kDa-bands. According to the densitometric analysis (Fig. 2), the five major soluble components represent 83.71% of the soluble protein fraction. Furthermore, the content of the casein fraction and α–La is 69.86% and 6.92%, respectively.
Mentions: The SDS-PAGE profile of soluble proteins of the untreated reconstituted skim milk is shown in Fig.1, while densitometric analysis is shown in fig. 2.

View Article: PubMed Central

ABSTRACT

This paper deals with the investigation of the impact of the heat treatment of reconstituted skim milk conducted at different temperatures, and the adding of demineralized whey on the protein solubility, soluble protein composition and interactions involved between proteins in a chemical complex. Commercial skim milk has been reconstituted and heat treated at 75°C, 85°C and 90°C for 20 minutes. Demineralized whey has been added in concentrations of 0.5%, 1.0 and 2.0%. The soluble protein composition has been determined by the polyacrilamide gel electrophoresis (SDS-PAGE) and by the densitometric analysis. Due to the different changes occurred during treatments at different temperatures, proteins of heat-treated samples containing added demineralized whey have had significantly different solubility. At lower temperatures (75°C and 85°C) the adding of demineralized whey decreased the protein solubility by 5.28%-26.41%, while the addition of demineralized whey performed at 90°C increased the soluble protein content by 5.61%-28.89%. Heat treatments, as well as the addition of demineralized whey, have induced high molecular weight complex formation. β-Lg, α-La and κ-casein are involved in high molecular weight complexes. The disulfide interactions between denatured molecules of these proteins are mostly responsible for the formation of coaggregates. The level of their interactions and the soluble protein composition are determined by the degree of temperature.

No MeSH data available.


Related in: MedlinePlus