Dear Susanne,

 

We may be “on dangerous grounds” here J

Please note that we are trying to be very precise in our definitions (but with some overlaps and maybe with wrong terminology)  – which is fine – however, we need to keep in mind that the energy factors used in the different systems are very, very rough averages.

As Rakesh indicated, all compounds differ in their measure for heat of combustions, the longer the chain the larger the heat of combustion (energy factor).

In addition, some Chebi definitions may come from us (EuroFIR) – Ian Unwin will know that.

 

I think that you should stick to the IUPAC definitions for fatty acids (http://goldbook.iupac.org/F02330.html), which says

Aliphatic monocarboxylic acids derived from or contained in esterified form in an animal or vegetable fat, oil or wax. Natural fatty acids commonly have a chain of 4 to 28 carbons (usually unbranched and even-numbered), which may be saturated or unsaturated. By extension, the term is sometimes used to embrace all acyclic aliphatic carboxylic acids.

 

The definition’s extension include some of the “organic acids”, the very short chain carboxylic acids (F2:0 and F3:0), but there are quite a lot of other “organic acids” (carboxylic acids), which are not necessarily “usually unbranched and even-numbered”.

Please also note that the term “organic acid” is not defined in the IUPAC system – the correct term is carboxylic acid - I may get into trouble here J

 

In the explanation of the Atwater system  by Merrill and Watt, a few “organic acids” are listed (USDA AH 74, one of the USDA classics, http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/Classics/ah74.pdf):

 

 

and we could add other “organic acids” like propionic/propanoic acid, sorbic acid, etc., commonly appearing in foods both naturally and as food additives.

And yes, you see vitamin C (ascorbic acid) among the “organic acids”, and if you want to be very precise, you should count the energy from the ascorbic acid too.

But “being precise” and  “energy calculation” is a contradiction J

 

Be pragmatic:

fatty acids are carboxylic acids with “a chain of 4 to 28 carbons” - fat energy factor 37kJ/g (9 kcal/g) in EU regulation – the rest – among these F2:0 and F3:0 (although pion means fat in Greek (from Wikipedia)) - are currently “organic acids” with energy factor 13 kJ/g (3 kcal/g) in EU regulation.

 

All the best,

Anders  

 

 

Anders Møller

Danish Food Informatics

Borgediget 12

DK-4000 Roskilde, Denmark

 

Websites:  Danish Food Informatics (http://www.danfood.info)

                      SciName Finder (http://www.sciname.info)

                      LanguaL(http://www.langual.org)

                     

 

 

From: Food Composition Discussion Group [mailto:[log in to unmask]] On Behalf Of Susanne Westenbrink
Sent: 24 January 2014 10:48
To: [log in to unmask]
Subject: energy factor for acetic acid and other organic or fatty acids

 

Dear all,

Many thanks to Esther, Erling, Anders, Rakesh and Paul for replying to our question. This has helped to get things clearer.
We do use the European legislation to calculate energy in foods, which means that we apply specific factors for e.g. organic acids and polyols. My main question was about where to put acetic acid, as this compount is both indicated as organic acid and fatty acid F2;0. So far we only have zero values in our database, so any change will not have an inpact on energy values. When adding an acetic acid value for vinegar and related foods we need to apply the correct approach.

From the discussion we have concluded that acetic acid (F2:0) must be treated as an organic acid and not as fatty acid. Acetic acid it is a building block of natural fatty acids but, unlike them, does not occur in natural triglycerides (Chebi). And 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, as indicated by Anders. In the NEVO database we will attribute ~3 kcal /g organic acids, and not include acetic acid in the sum of saturated fatty acids.

To continue the discussion:
Following this, the next question pops up for other short chain fatty acids/organic acids. On internet (http://www.cyberlipid.org/fa/acid0001.htm#1) I found information that stated that short chain fatty acids (below 4- 6 Carbons) should/could be regarded as organic acids. Up to 6 (or 4) carbon atoms, organic acids are considered "short-chain organic acids", they have substantial solubility in water. Furthermore, they do not behave physiologically like other fatty acids since they are more rapidly digested and absorbed in the intestinal tract and have unique properties in regulating sodium and water absorption through the mucosal epithelium. Biochemically, they are more closely related to carbohydrates than to fats. However I am not sure how reliable this website is.

Propanoic acid is listed as organic acid in the EuroFIR component thesaurus and as fatty acid by Chebi (I could not find it in the INFOODS tagnames). Is this measured through fatty acid analyses methods? Is it a relevant component in food?  If available in a food comp database, should 3 or 9 kcal be calculated for energy?
What is your opinion on this?

Butyric acid (F4:0) is classified as fatty acid in both the EuroFIR component thesaurus and the Chebi database. I know this is measured in fatty acid analyses, we have several values. My conclusion would be that F4:0 must be treated as a fatty acid, yielding ~ 9 kcal/g. (This what we have been doing all the time).
Do you agree on this conclusion for  butyric acid?


EuroFIR component thesaurus:
Acetic acid classified as organic acid, with synonym F2;0
Propanoic acid: classified as organic acid with synonym F3;0

Butyric acid classified as saturated fatty acids (F4:0)

Chebi database:

Acetic acid F2:0 Chebi 15366: building block of natural fatty acids which, unlike them, does not occur in natural triglycerides.
Propanoic acid F3:0 chebi 30768: The smallest H(CH2)nCOOH acid that exhibits the properties of the other fatty cids.
Butyric acid F4:0 Chebi 30772: four carbon straight-chain saturated fatty acid

Looking forward to your reaction,
with best wishes,
Susanne and Martine


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://nevo-online.rivm.nl




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