Physical characteristics determine whether the glucose molecule can be metabolized for energy and how it affects your health. When some characteristics of a glucose molecule change, it actually becomes a different sugar. And when you cook, several different qualities determine the way your dishes turn out.
Glucose exists in a variety of shapes, and the two most basic are L-glucose and D-glucose. Both forms have the same chemical composition, but their component particles are arranged as mirror images of one another.
These different shapes, called isomers, are significant characteristics because they determine how the sugar works inside your body. D-glucose, also known as dextrose, is a simple sugar that naturally occurs in carbohydrates and helps fuel your body. L-glucose is also a simple sugar, but your body can't metabolize it for energy.
Glucose can also form a ring-shaped structure that has two additional isomers. However, these forms connect together to form large molecules of starch and cellulose, complex carbs with different properties than L-glucose.
Size and Solubility
L-glucose is a tiny molecule, even smaller than a red blood cell or the thin membrane that surrounds cells. It also dissolves in water. Both of these characteristics are vital when it comes to your health. They allow glucose to be rapidly digested, absorbed into the bloodstream and easily carried through water-based body fluid.
The molecule's size and solubility helps give you quick boost of energy after you consume glucose-containing carbohydrates, such as grains and fruits. On the other hand, these characteristics also mean glucose can spike blood sugar, which can lead to weight gain and cause health problems if you’re diabetic.
Glucose is a white, sweet-tasting powder, so it can be used as a sweetener, but it’s usually combined with other sugars. On a relative sweetness scale, glucose has a score of 0.74, compared to fructose, with a rating of 1.74. They’re combined in equal amounts to make sucrose, or table sugar, which has a sweetness level of 1.
Glucose and fructose have the same amount of carbon, oxygen and hydrogen, but in each sugar, the particles are arranged into slightly different shapes. The unique shapes determine whether it’s fructose or glucose, as well as the level of sweetness.
Impact in Cooking
Several physical characteristics of glucose, as well as sucrose and other sugars, affect their role in food preparation. Along with the obvious benefit of boosting sweetness, the sweet characteristic of sugar improves or diminishes other flavors. For example, sugar is added to tomato sauce to reduce its acidic flavor.
Sugar’s solubility and tendency to absorb water help tenderize yeast-based dough and add thickness to beverages. Its freezing point prevents crystals from developing in frozen foods. The melting point of glucose, fructose and sucrose is especially important in cooking. As sugars reach their melting point, they caramelize, contributing brown coloring and depth of flavor.
- Rensselaer Polytechnic Institute: Carbohydrates – Sugar and Polysaccharides
- University of Bristol: Molecule of the Month: Glucose
- Science of Cooking: Molecules of Taste – Glucose
- Intermediate Physics for Medicine and Biology; Russell Hobbie and Bradley Roth
- PubChem: D-Glucose
- Kimball’s Biology Pages: Carbohydrates
- University of Illinois: Taste Receptors
- Canadian Sugar Institute: Functional Properties of Sugar