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
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The Netherlands
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