Riporto di seguito un testo tratto direttamente dal Danish Food Composition Databank / Database, che è curato dal Dipartimento di Nutrizione del National Food Institute della Technical University of Denmark (DTU):
Carbohydrates
This version of the Danish Food Composition Databank distinguishes between two specifications of carbohydrate, total carbohydrate and available carbohydrate. This is due to the new energy calculation procedures introduced in the Nordic Nutrient Recommendations [2], which uses available carbohydrate and dietary fibre with different energy conversion factors in the calculation where previously total carbohydrate was used.
Generally, the total carbohydrate content has been calculated by difference, defining carbohydrate as:
- total carbohydrate [g/100 g] =dry matter [g/100 g] - (protein [g/100 g] + fat [g/100 g] + ash [g/100 g])
while available carbohydrate here is defined as:
- available carbohydrate [g/100 g] =total carbohydrate [g/100 g] - dietary fibre [g/100 g])
This calculation method introduces errors in the result as errors in the determinations of dry matter, protein, fat, ash - and for available carbohydrate also dietary fibre will influence the final total carbohydrate value. In many cases these errors are equalized though.
The total carbohydrate by difference value includes - apart from the components usually regarded as carbohydrates - also other carbon containing compounds like organic acids, lignins and tannins. It is with this carbohydrate definition Atwater has based his energy factor for carbohydrate.
All carbohydrate values are expressed as g/100 g edible part.
References:
[2] Levnedsmiddelstyrelsen, Ernæringsenheden: Næringsstofanbefalinger 1989. København, 1989.