Dextrose equivalent (DE) is a measure of the amount of reducing sugars present in a sugar product, relative to dextrose (a.k.a. glucose), expressed as a percentage on a dry basis. For example, a maltodextrin with a DE of 10 would have 10% of the reducing power of dextrose (which has a DE of 100). Maltose, a disaccharide made of two glucose (dextrose) molecules, has a DE of 52, correcting for the water loss in molecular weight when the two molecules are combined (180/342). Sucrose actually has a DE of zero even though it is a disaccharide, because both reducing groups of the monosaccharides that make it are connected, so there are no remaining reducing groups. For solutions made from starch, it is an estimate of the percentage of reducing sugars present in the total starch product.
In all glucose polymers, from the native starch to glucose syrup, the molecular chain begins with a reducing sugar, containing a free aldehyde. As the starch is hydrolysed, the molecules become shorter and more reducing sugars are present. Because different reducing sugars (e.g. fructose and glucose) have different sweetness, it is incorrect to assume that there is any direct relationship between DE and sweetness.
The DE describes the degree of conversion of starch to dextrose:
- starch is close to zero,
- glucose/dextrose is 100 (percent),
- dextrins vary between 1 and 13,
- maltodextrins vary between 3 and 20
- glucose syrups contain a minimum of 20% reducing sugars.
The DE gives an indication of the average degree of polymerisation (DP) for starch sugars. The rule of thumb is DE × DP = 120. The standard method of determining DE is the Lane-Eynon titration, based on the reduction of copper(II) sulfate in an alkaline tartrate solution,p. 230 an application of Fehling's test.
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