ANTIOXIDANT CAPACITY OF ORANGE JUICE MULTIPLIED TENFOLD
The antioxidant
activity of citrus juices and other foods is undervalued. A new technique
developed by researchers from the University of Granada for measuring this
property generates values that are ten times higher than those indicated by
current analysis methods. The results suggest that tables on the antioxidant
capacities of food products that dieticians and health authorities use must be
revised
Orange juice and
juices from other citrus fruits are considered healthy due to their high
content of antioxidants, which help to reduce harmful free radicals in our
body, but a new investigation shows that their benefits are greater than
previously thought.
In order to study
these compounds in the laboratory, techniques that simulate the digestion of
food in the digestive tract are used, which analyse only the antioxidant
capacities of those substances that can potentially be absorbed in the small
intestine: the liquid fraction of what we eat.
"The problem is
that the antioxidant activity of the solid fraction (the fibre) isn't measured,
as it's assumed that it isn't beneficial. However, this insoluble fraction
arrives at the large intestine and the intestinal microbiota can also ferment
it and extract even more antioxidant substances, which we can assess with our
new methodology," José Ángel Rufián Henares, professor at the University
of Granada, explains.
His team has developed
a technique called 'global antioxidant response' (GAR), which includes an in
vitro simulation of the gastrointestinal digestion that occurs in our body,
whilst taking into account the 'forgotten' antioxidant capacity of the solid
fraction.
The method, the
details of which are published in the journal 'Food Chemistry', includes
assessments of various physical and chemical parameters, such as colour,
fluorescence and the relationship between the concentrations analysed and
compounds indicators such as furfural.
Upon applying the
technique to commercial and natural orange, mandarin, lemon and grapefruit
juices, it has been proved that their values greatly increase. For example, in
the case of orange juice, the value ranges from 2.3 mmol Trolox/L (units for
the antioxidant capacity) registered with a traditional technique to 23 mmol
Trolox/L with the new GAR method.
"The antioxidant
activity is, on average, ten times higher than that which everyone thought up
until now, and not just in juices, but also in any other kind of food analysed
with this methodology," highlights Rufián Henares, who notes its possible
application: "This technique and the results derived from it could allow
dieticians and health authorities to better establish the values of the
antioxidant capacity of foods."
With the help of this
method, scientists have also created a mathematical model in order to classify
juices according to their natural and storage conditions, which ensures that
the correct raw materials and sterilisation and pasteurisation processes are
used.
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