Figure 3 - uploaded by Bjørn Petrat-Melin
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Schematic representation of the proposed structure of the casein (CN) micelle in milk. αsand β-caseins (orange) interact electrostatically with calcium-phosphate nanoclusters (grey) to stabilize the interior network. Some β-CN (blue) interact through hydrophobic interactions to the other CNs. κ-CN is located on the surface of the micelle (green), with its hydrophilic caseinomacropeptide extended outward (black). (Adapted from Dalgleish and Corredig, 2012).
Source publication
This thesis describes possible physiological consequences of genetic variation in bovine beta- and kappa-casein. These caseins constitute approximately 40% of the protein in bovine milk, and are known sources of a number of bioactive peptides, which are protein fragments that are believed to exert health-promoting effects. The studies revealed that...
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Milk is a heterogeneous lacteal secretion mixture of numerous components that exhibit a wide variety of chemical and functional activities. Casein, the main protein in milk, is composed of α -, β -, and κ -caseins, each of which is important for nutritional value and for promoting the release of cytokines, also are linked to the regulation of haema...
Citations
... Since β-CN is the most hydrophobic among caseins (αand κ-CN) (Cheng et al., 2020) and it is loosely bound to the other caseins through hydrophobic interactions, it tends to dissociate when these hydrophobic bonds are weaker by lowering the temperature to 4 • C (Pierre & Brule, 1981). The cold solubilzation allow the recovery of a mixture of β-CN variants which are A1, A2 without preference for a genetic variant in agreement with previous works (Petrat-Melin, 2014;Petrat-Melin et al., 2015). ...
Emulsifying properties and in vitro antioxidant and antimicrobial activities of the isolated camel and bovine β-casein (β-CN) were investigated and compared. Antioxidant assay showed that both β-CN had significant reducing power, iron chelating and antiradical activities especially for camel β-CN. Camel β-CN also exhibited strong antifungal activities against Aspergillus tamarii and Aspergillus sclerotiorum. The maximum emulsion activity was achieved by both β-CN samples at pH 7.0 and 9.0 than 5.0, with higher values for the camel β-CN. This behavior was linked to the relative high electronegative charge and interfacial properties of proteins under conditions away from their isoelectric-point as confirmed by the ζ-potential and interfacial tension measurements. Further, the stability of emulsions decreased at pH 5.0 because of the β-CN precipitation and aggregation despite its high surface hydrophobicity. This study concluded that the camel β-CN has antimicrobial, antioxidant, and techno-functional properties in agricultural and food industries.
... This method is useful as it combines both predicted and measured absorbance, which gives a better estimation of the absolute protein content. Purification of b-CN by cold storage and ultracentrifugation is simple and limits the risk of changing the physiochemical properties of the proteins, as could occur with urea-based methods (O'Mahony & Fox, 2013;Petrat-Melin, 2014). ...
... As explained earlier, the peptide bond N-terminal to residue H 67 is considered more prone to cleavage by proteolytic enzymes than P 67 ; hence, the cleavage may occur at a higher rate when H is present. However, duodenal protease activity increases with time, making sites of cleavage more diverse, and residues Q, S, P and N were also observed as effective cleavage sites, as previously reported by Petrat-Melin (2014). This suggests that the residue P 67 of variant A2 and I may also affect the proteolytic cleavage. ...
This study investigated whether different genetic variants of β-CN give rise to different bioactive peptides during digestion. β-CN was purified from bovine milk of genetic variants A1, A2 and I, and digested with human gastrointestinal juices in a static ex vivo model. Mass spectrometry analyses revealed that the peptide ⁶⁰YPFPGPIPN⁶⁸ was exclusively identified from variants containing proline at position 67. Most strikingly, the opioid peptide β-casomorphin-7, ⁶⁰YPFPGPI⁶⁶, was identified from both variants A1 and A2 after simulated digestion, though with concentration being somewhat higher after digestion of the variant A1, compared with variants A2 and I. The peptides ¹³⁴HLPLP¹³⁸ and ¹³³LHLPLP¹³⁸ were both identified after initial 5 min of duodenal digestion. In conclusion, genetic variation of β-CN may affect proteolysis during digestion; however, the release of BCM7 does not seem to be linked solely to variant A1, as earlier suggested by relevant published literature on in vitro digestion.
