Milk protein may act as effective delivery vehicle for blueberry nutrients

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Based on study findings, the team strongly believe the α-casein protein could promote the absorption of blueberry anthocyanins and their metabolites in the blood, improving their bioavailability in vivo​.

“Molecular docking showed that anthocyanins could dock into the structural cavity of α-casein and interact with the amino acid residues,”​ states the researchers from Shenyang Agricultural University in China.

“We will illustrate the specific mechanism of the promotional effect of α-casein on the bioavailability of anthocyanins and their metabolites in future studies.”

The research team began feeding rats purified blueberry anthocyanin extracts, adding α-casein to the solution given to one group of rats.

Over the next 24 hours, anthocyanin and metabolite concentrations were 1.5 to 10.1 times higher in the α-casein group than in the control rats.

When examining α-casein’s molecular structure, the researchers observed that its amino acids allowed it to interact with and encapsulate the anthocyanin molecules, improving their stability in the intestines and allowing for better transport into the bloodstream.

Whole milk difference?

While the α-casein protein used in these experiments was derived and purified from milk, the results may not be the same for whole milk because its fats and sugars could impact absorption.

“We noticed that most of these research studies were conducted with whole milk, not with the purified protein derived from the milk,”​ the research team comments.

“Therefore, we reckoned that the compounds in milk, such as saccharides and fats, could also impact the bioavailability of polyphenols, causing the negative outcomes.

“Moreover, the ratio of protein to polyphenols was also vital to the effects because a high concentration of proteins might make it harder to release the polyphenols during intestinal digestion.”

In discussing the results’ significance, the team revealed that three main anthocyanin monomers (D3G, C3G, and M3G) were detected in rat plasma.

“The absorption of M3G with high content in original blueberry anthocyanins was poor in rat plasma compared with D3G and C3G,”​ they say.

In reference to one study​, the team confirmed that different structures of anthocyanin monomers would affect their absorption in plasma.

Food matrix impact

Anthocyanin absorption could also be affected by food matrixes, the team adds one report​demonstrating that citrus pectin could increase the intestinal accessibility of blueberry anthocyanins.

In addition, many researchers provided evidence of the positive effects of protein on anthocyanins although these studies mostly focused on the in vitro conditions.

Investigations associated with the effects of protein on anthocyanins in vivo were limited with the team’s previous studies showing that α-casein improved the stability of blueberry anthocyanins under processing and digestive conditions.

“On the basis of these results, the effects of α-casein on the absorption of blueberry anthocyanins in rats were further detected in this study.”

Source: Journal of Agricultural and Food Chemistry

Published online: DOI: 10.1021/acs.jafc.1c00082

“Effects of α-Casein on the Absorption of Blueberry Anthocyanins and Metabolites in Rat Plasma Based on Pharmacokinetic Analysis.”

Authors: Yuxi Lang et al.

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