The antioxidant activity of orange juice and juices from
other citrus fruits is undervalued, suggests a new technique developed by
researchers from the University of Granada.
Current techniques involve analyzing only the antioxidant
capacities of those substances that can potentially be absorbed in the small
intestine- the liquid fraction of what we eat, and not measuring the antioxidant
activity of the solid fraction (the fiber), whilst assuming that it is not
Josngel Rufin Henares, professor at the University of
Granada, said, "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."
The new technique called 'global antioxidant response'
(GAR), which includes an in vitro simulation of the gastrointestinal digestion
that occurs in our body, taking into account the 'forgotten' antioxidant
capacity of the solid fraction. On applying the technique to commercial and
natural orange, mandarin, lemon and grapefruit juices, it has been proved that
the values generated are ten times higher than those indicated by current
analysis methods. For example, in case of orange juice, the value ranges from
2.3 mmol Trolox/L registered with a traditional technique to 23 mmol Trolox/L
with the new GAR method.
These results suggest that tables on the antioxidant capacities
of food products used by dieticians and health authorities must be revised. Using
this method, scientists have created a mathematical model to classify juices
according to their natural and storage conditions, which ensures that the correct
raw materials and sterilization and pasteurization processes are used.
The study is published in the journal 'Food Chemistry'.