Of course, one might expect limonene to be a minor
component in the juice and we can see that this is
the case, as limonene is very hydrophobic. I should
note that limonene is an insignificant contributor to
aroma or character and as such might be considered
a carrier or flavor delivery substance.
While many oxygenated components and aldehydes are major contributors to the grapefruit
aroma, it is the esters that provide the fruity body.
However, the most characterizing components in
grapefruit are the sulfur-containing constituents,
along with nootkatone, that play the most important
role for character. It is a combination of several
sulfur components that exist in grapefruit, the single
most important one is grapefruit mercaptan (see F- 3
and F- 4).
Without these sulfur containing components,
grapefruit would smell very much like orange, which
is often used to blend with grapefruit during shortage conditions, which unfortunately happens much
When I have the opportunity to work with natural
products and go through a direct extraction and
analysis, there are often surprises and lessons to be
learned. In this case, the lesson was clear. Fructose,
as well as other sugars are often in an acidic medium
in the natural product or botanical. The subsequent
reaction products of furfural, hydroxy methyl furfural, as well as pyrones, lactones and other related
molecules are bound to be formed either naturally,
or as a result of thermal or other reaction drivers.
Upon reflection over my own personal history of
extraction and analysis, it is evident why so many
fruits, which naturally contain fructose, would
develop—as part of their aroma and flavor profile—a
sweet cooked characteristic. This is usually due to
maltol, which we can see is a result of decomposition
of sugars in an acidic environment.
In a short sentence, what comes out of a gas
chromatograph may not be an indicator of what was
put into the injection port.
1. Assry, Rajeev S., Mechanistic Insights into the Decomposition
of Fructose to HMF. The Journal of Physical Chemistry, ACS
2. Rosatella, A. A. (2011). 5-Hydroxymethylfurfural (HMF) as a
building block platform: Green Chemistry, 13( 4), 754-793.
F-3: Grapefruit mercaptan
F-4: 3-Mercapto hexanol