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Coke with vanilla flavour, cigarettes with menthol taste: people want their
food to taste extraordinary. Citrus species have a special compound, which
affects fruit flavour. By modulating the quantities of this compound,
researchers are now creating foods with new tastes. Since the ingredients
also benefit human health, it could be possible to make ?unhealthy? foods,
healthier ? a great advantage for countries, where there is a deficiency of
fruit February 2005 by Kathrina Schoebi, Checkbiotech .


Citrus species contain large quantities of special ingredients called
flavanones, which affect fruit flavour and benefit human health. Flavanones
are important dietary components with a role in maintaining healthy blood
vessels and bones. Furthermore, they suppress cancer and mutagenesis and are
known to prevent allergies, reduce inflammation and act as anti-microbial
compounds.

Citrus species are one of the major sources of flavanones in the human diet
and a major source of these compounds for the food and para-pharmaceutical
industries. There are two sorts of flavanones: a bitter one, causing the
bitter taste of species such as grapefruit and pummelo, and a tasteless one,
being responsible for the flavour of non-bitter species such as mandarin and
orange. The production of the bitter and the tasteless flavanones is
catalysed by two different forms of enzymes.

Citrus flavanones are synthesized in large quantities in young tissues of a
plant such as leaves, flowers or fruit. Later on, they are diluted in the
fruit to their final concentration during the process of development and
ripening. The biological role of the flavanones in citrus fruit has not been
proved, although increasing evidence points to a role in plant defense.

A research team headed by Yoram Eyal, from the Institute of Horticulture in
the Volcani Center in Israel, isolated and characterised the gene encoding a
special enzyme, which is responsible for the production of the bitter
flavanones. They published their results in The Plant Journal.

Personlized tastes

Yoram Eyal and his colleagues used pummelo for their experiments. In pummelo
contains an enzyme, which catalizes the production of the bitter flavanones.
Once the genes encoding the enzymes were isolated and characterized, the
researchers could use these genes for further experiments. They are now
engaged in a project with collaborators, in which they produce less-bitter
varieties of grapefruit through genetic engineering.

Dr. Eyal said his research could bridge a gap in the market, since many
people do not care for the bitter taste of grapefruits. Likewise, it would
be possible to change original non-bitter fruit, such as oranges, into tart
or bitter fruit.

There is another advantage of genetically modified fruit and vegetables. By
producing flavanones in fruits or vegetables other than citrus varieties,
the flavour of these fruits or vegetables would be affected. So it would be
possible to produce tarter (not necessarily more bitter) tomatoes by
enhancing them with bitter flavanones (in lower concentrations than they
occur in grapefruit).

Healthier foodstuff

When asked, if it could be possible to have healthier fruit through
genetically engineering Dr. Eyal answered, ?It would be of interest to study
what happens if you prolong synthesis of flavanones (beyond the young tissue
stage) and obtain higher levels of flavanones in the mature fruit. This
would be of interest both at the plant-physiological level and as a
potential product with increased flavanone content.?

Dr. Eyal is sure that flavanones, once being produced in microorganisms,
could be incorporated into processed foods such as pasta, since they are
relatively stable. By so doing, it might give rise to ?healthy? pasta, or
ultra-bitter dark chocolate on the market.

?But at the personal level, I always have mixed feelings when people refer
to developing healthier foods, since individuals that eat a balanced diet
may not need any health-enhancement of the current fruit, vegetables and
processed foods.?

?On the other hand, individuals that have less access to fresh fruit and
vegetables (or have access to a small range of fruit and vegetables) may
indeed benefit from flavonoid-enriched foods.?

Last but not least, with Dr. Eyal?s results, it could be possible to develop
a biologically-based production system for a semi-natural low-calorie
sweetener. Dr. Eyal recently submitted his research with sweeteners to a
scientific journal for publication, and it is currently being reviewed.

With Dr. Eyal?s research, the food and nutraceutical market have taken a
step forward. The big step, as Dr. Eyal said, is still ahead of us and
relies on the success of the transgenic approaches in plants and
microorganisms.

In the future, we might expect to find fruit and vegetables with unusual
flavours in supermarkets, personalized to tempt our appetite. And who knows,
maybe in a few years, we will be eating citrus flavonoid enriched spaghetti
and chocolate!

[www.checkbiotech.org];
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