Types of starch

Classification and classes of starch

What is starch and how is it classified?

Starch is a type of complex carbohydrate found in most starchy foods, such as cereals (refined and whole grains), tubers and roots, legumes, and vegetables.

How is starch like?

Chemically, starch is a tree-shaped molecule that is formed by the union of different molecules, amylose and amylopectin, which, in turn, are both made up of glucose.

Types of starch

Starch can be classified into different types:

  • Rapidly digestible starch
  • Slowly digestible starch
  • Resistant starch

Characteristics of rapidly digestible starch

Boiled potato with spinach
Boiled potato with spinach. The starches present in the boiled potato take very little time to be absorbed.

It is usually gelatinized starch (amylopectin) that is found in abundance in foods rich in starches cooked at high temperatures, such as potatoes, bread, or rice when they are highly cooked.

During digestion, this type of starch takes less than 20 minutes to convert to glucose (sugar). Therefore, although they are complex carbohydrates, their digestion and absorption is quite fast, which, in excess, makes it more difficult to control glycemia (blood sugar levels) and are more problematic for diabetes.

In English it is abbreviated as RDS (Rapidly Digestive Starch)

Characteristics of slowly digestible starch

It is a type of starch more difficult to break down by digestive enzymes, which take about 100 minutes to convert to glucose.

It is found in short-cooked starch-rich grains, such as pasta al dente, lightly cooked rice, undercooked potato, … It is more tolerable than the previous one for people with obesity and diabetes.

In English it is abbreviated as SDS (Slowly Digestive Starch).

Classification of starch
Classification of starch and the types of resistant starches (retrograde starches) that exist. Starchy foods in the diet contain a mixture of these, but through cooking and cooling we can modify the proportion of these. The most interesting is type 3 resistant starch due to its high fermentative or prebiotic properties.

punto rojo More information on starch and carbohydrates

Elisenda Carballido
Written by Elisenda Carballido Dietitian nutritionist. Postgraduate in Phytotherapy and master in Nutrition and Metabolism.

17 March, 2020

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