Dear Martine and Susanne
Both Esther and Paul are right.
I will complicate the matter a little, though, because you did not tell us
by which system you calculate the energy J
Which factor to use is dependent on the energy calculation system you are
referring to.
In the specific and general Atwater systems, the energy calculations include
only the proximates. Specific energy factors take into account the
contribution of acetic acid.
Similarly, basically the Rubner and British systems are based on proximate
composition and do go into details about organic acids.
For these systems, the purpose of energy calculations are the estimation of
energy for the whole (average) diet, not the specific foods.
Organic acids are mentioned by Merrill and Watt in USDA AH 74 in their
explanation of the USDA (Atwater) system. They conclude that the organic
acids make up only a very small amount in the average diet. Therefore,
organic acids are not taken into account in these energy calculations.
However, if your system is European nutrition labelling, and you are
speaking about single foods, a large amount of fruits – and vinegar as you
mention - contain non-negligible amounts of organic acids.
That is why the system used nutrition labelling in European legislation
includes specific factors for organic acids - which indeed can be regarded
as very short chain fatty acids – but with the usual analytical methods,
they do not turn up in the value for fat/fatty acids. You need special
analytical methods to determine the amount of organic acids.
The energy value for organic acids in the labelling context is defined as 13
kJ/g (3 kcal/g) – the value Paul gave.
You may have a similar question concerning polyols, which are sugar
alcohols, and usually included in the carbohydrate value.
However, in European labelling, polyols should be subtracted from the
carbohydrate value before calculation energy, but that is a completely
different story !-)
All the best,
Anders
From: Food Composition Discussion Group
[mailto:[log in to unmask]] On Behalf Of Susanne
Westenbrink
Sent: 21 January 2014 14:34
To: [log in to unmask]
Subject: energy factor for acetic acid?
Dear all,
We have got a question concerning acetic acid.
In the EuroFIR thesaurus this acid is assigned to the organic acids, but
with the synonym: fatty acid C2:0.
Our question is: how to deal with the energy calculation if a food, for
instance vinegar, contains acetic acid. Is the amount of acetic acid
multiplied by the energy factor for fat or for organic acids? Does any of
you know more about the energy from acetic acid? And how did you deal with
this in your food composition databases?
Kind regards,
Martine Jansen en Susanne Westenbrink
Susanne Westenbrink
Rijksinstituut voor Volksgezondheid en Milieu (RIVM) / National Institute
for Public Health and the Environment
Centrum voor Voeding, Preventie en Zorg / Centre for Nutrition, Prevention
and Health Services
PO Box 1
3720 BA Bilthoven
The Netherlands
tel: +31 (0) 30 274 2448
fax: +31 (0) 30 274 4466
e-mail: [log in to unmask]
for more information on the Dutch food composition database see
<http://www.rivm.nl/nevo> http://www.rivm.nl/nevo
<http://nevo-online.rivm.nl/> http://nevo-online.rivm.nl
<http://www.rivm.nl/Proclaimer>
Proclaimer RIVM http://www.rivm.nl/Proclaimer
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