Researchers from the Technical University of Denmark and the University of Copenhagen reported that the new study’s findings follow on from previous research identifying the possibility of natural antioxidants in yogurt - an article on the first study can be found here.
The new research, reported in the journal Food Chemistry, goes a step further by pinpointing exactly which yogurt proteins have antioxidant properties.
“Characterisation of the peptides, as well as identification of the exact sequence of amino acid conferring antioxidant activity, makes it possible to synthesise and purify these antioxidant peptides for their application in foods as natural antioxidants” stated the researchers.
Antioxidant Identification
The new study characterised the proteins in yogurt fractions (sizes - 30, 10 and 3 kDa) in order to identify proteins with high antioxidant activity.
The study discovered that all of the peptides previously found to be anti-oxidative contained residues of the amino acid proline, a finding that supports previous research suggesting antioxidant activity could be linked to proline content.
A large proportion of antioxidant peptides were also found to contain the hydrophobic amino acid residues valine or leucine at the N-terminus, which is consistent with the findings of previous research that suggests they have a strong link to antioxidants.
In addition, the yoghurt contained a considerable amount of free amino acids (histidine, tyrosine, methionine and cysteine), which have been reported to have antioxidant properties.
The researchers wrote: “It is evident from our results that the peptides released have an important role in the oxidative stability of yoghurt. The 3–10 kDa fraction revealed many peptide sequences that correlated with antioxidant peptides previously reported by others.”
Stable Functional Foods
Previous research had suggested that natural antioxidant proteins formed during the fermentation of milk into yogurt could be used as a functional ingredient, adding oxidative stability to foods enriched with omega-3 oils.
“Our findings suggest that the presence of antioxidant peptides and free amino acids in fish oil-enriched yoghurt may have significantly contributed to its high oxidative stability. These results also demonstrate the applicability of these naturally occurring antioxidant peptides as an ingredient in foods in order to increase their oxidative stability” concluded the researchers.
Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodchem.2010.05.029
“Antioxidant activity of yoghurt peptides: Part 2 – Characterisation of peptide fractions”
Authors: K.H.S Farvin, C.P. Baron, N.S. Nielsen, C. Jacobsen