Sacarid — Carbohydrate Chemistry | sacarid.com
The reference scale, where common sugars fall on it, and what the numbers actually measure.
The glycaemic index compares the blood-glucose response to a food or sugar against a glucose reference set at 100. It is a ranking per unit of available carbohydrate, not per gram of food and not per unit of sweetness.
Glucose is 100 by definition. Sucrose is about 65, because it is half glucose and half fructose and the fructose half is metabolised largely in the liver. Fructose alone is about 19.
On narrow screens, swipe or scroll the plate sideways.
These values do not track molar mass. Sucrose at 342.30 g/mol and glucose at 180.16 g/mol sit on different rungs of the mass ladder, yet the index is about absorption and metabolism rather than molecular weight.
The index also does not rank sweetness. Fructose is very sweet and sits low; glucose is less sweet and sits at the top. The scale is about blood-glucose response, and that is a different question from taste.
Values are approximate and depend on the reference scale and the test protocol. They are useful for comparison, not for precise prediction in an individual.
Further reading