The study, published in the Journal of Agriculture and Food Chemistry, shows that common food flavonoids may act as “excellent stabilizers” of oil-in-water emulsions, and suggests that role of ‘stabilizer’ in an emulsion may increase the bioavailability of such compounds by delivering them to the gut without the need for more complex techniques such as encapsulation.
Researchers from the University of Leeds, explained that the compounds stabilise the emulsions due to “a tendency for accumulation at the Oil−Water interface” which in some cases “can provide very good stabilization of oil-in-water (O/W) emulsions.”
“Understanding of the physicochemical properties of flavonoids is probably the first step in trying to rationalize their bioavailability,” said the authors, led by Brent Murray, Professor of Food Colloids at the University of Leeds.
They added that the results of the study “may be highly significant with respect to the delivery of such insoluble compounds to the gut, as well as their digestion and absorption.”
Flavonoids are a group of polyphenol plant metabolites that have generated considerable interest in recent years due to their association between dietary consumption and health benefits.
The compounds have been suggested to have many healthy benefits, the evidence for which has come mainly from studies of their in vitro activity as antioxidant and anti-inflammatory agent, in addition to some in vivo animal studies.
But, according to the authors, “in order to fully understand the in vivo consequences of dietary flavonoid ingestion and to make sense of in vitro and animal studies, the processes of flavonoid absorption and metabolism need to be better understood.”
Prof. Murray and his colleagues said despite the occurrence of a considerable amount of flavonoids in the daily diet, flavonoids are generally known to have poor solubility in water.
According to the authors this has spurred “a large number of studies to try and encapsulate them with various structures that might aid their dispersibility, using similar strategies as for water-insoluble drugs.”
However, they said that by exploring the hydrophobic/hydrophilic nature of flavonoids, it may be possible to find solutions to the problem of solubility by using an emulsion.
The authors screened a wide range of flavonoids for their emulsification behaviour, noting that it is difficult to predict how good an emulsifier the flavonoid will be, based on the molecular structure of individual flavonoids.
The authors found that some common food flavonoids (including K7Neo, Q3R (rutin), N7Neo(naringin), N7R, and tiliroside) act as excellent stabilizers of oil-in-water emulsions, through their adsorption (as water-insoluble particles) to the surface of the oil droplets – forming a ‘coating’ around a large droplet, known as a Pickering emulsion.
Murray and co- workers said that the Picketing emulsion droplets formed by flavonoids in an oil/water emulsion are “a huge energy barrier to droplet shrinkage or coalescence, and the emulsions are very stable.”
Rutin and naringin were found to produce the finest emulsions, with droplet sizes of 6, and 5 micrometers (μm), respectively.
The researchers said the results may have significance with respect to the location of flavonoid compounds in real food systems, explaining that flavonoids may be delivered as part of a stable oil−water interface which occurs in foods containing emulsified oil.
As such, they added that the study holds promise for the transport and delivery of flavonoids, which are generally insoluble, to the gut without the use of more complex, and often expensive techniques such as encapsulation.
The results may also have an impact on the understanding of human digestion and absorption of flavonoids, said Murray and colleagues.
Source: Journal of Agriculture and Food Chemistry
Published online ahead of print, doi: 10.1021/jf1041855
“Particle-Stabilizing Effects of Flavonoids at the Oil−Water Interface”
Authors: Z. Luo, B.S. Murray, A. Yusoff, M.R. A. Morgan, M.J. W. Povey, A.J. Day