How Does Retrogradation Impact the Way we Digest Carbs

We have all been told about the benefits of eating leftovers, helping to save us money and precious time. But what if these leftovers could improve the nutritional value of our meals as well? Cooking, letting it cool, and then heating starchy meals like rice, pasta, and potatoes initiate an incredible transformation at a molecular level. Cooking and refrigerating these foods induce a remarkable biochemical reaction, known as retrogradation, making common starch molecules turn into a ‘super-foodstuff’ named Resistant Starch or RS.

It’s more than just kitchen folklore. It’s an actual scientific phenomenon with serious implications for your blood sugar control and your overall health.

Unlocking the Power of Retrogradation

The key process at the core of this process is retrogradation. It relates to the cooling and subsequent crystallization of gelatinized starch in food sources that have been cooked, like rice and potatoes. This process works on our body remarkably, making something that would be readily absorbed into a nutritious fiber.

The Science of the Changes

From Digestible to Resistant: With heating, starch undergoes gelatinization, in which starch granules increase in size, burst, and release their chains, which are then easily broken down by enzymes, quickly raising blood sugar readings."

The Retrogradation Effect: Upon cooling of the food, with overnight storage in a fridge, for example, the starch molecule chains, particularly amylose, re-arrange themselves and form compact crystalline structures. This brings about retrogradation.
The Outcome: The resultant, crystalline structure resists the digestive enzymes present in the small intestine, namely amylases. This converts a certain quantity of original digestible starch into Resistant Starch, also called RS3.

Effect on Digestion and Health

Lower Glycemic Index: Since RS3 passes without being converted to glucose in the small intestines, it delays the absorption of glucose in the bloodstream. Therefore, it reduces sugar levels in the bloodstream. A lower glycemic index provides a slowed blood sugar response, which is ideal for blood sugar control and energy.

Benefits for Gut Health:

Resistant starch passes unchanged into the large intestine, where it becomes a prebiotic fiber. Here, it undergoes fermentation by the favorable microbiota in the gut, yielding Short Chain Fatty Acids such as butyrate, which are essential for colon, anti-inflammatory, and possibly metabolic functions.

Food Applications:

Here are practical food applications to take advantage of this principle, for example:

 Potatoes: Boiling and cooling potatoes, as when making a potato salad, greatly enhances the RS value, which remains low when consumed warm, as when freshly cooked. 

Rice: Leftover and/or chilled rice contains a higher percentage of RS than fresh rice. I am ready to talk about the biochemical processes involved, when you ideally would want it to retrograde, as well as how it affects nutrition.

Frequently Asked Questions (FAQs)

1.            1. Does heating retrograded starch (such as chilled rice) destroy RS? 

Although there is a very slight loss of RS in some research conducted on reheating, a great deal of the desirable structure (the RS3) will still be intact. As a fact, there will still be a considerably higher amount of RS compared to the starch before it was heated. 

2. Which kind of food can be used for resistant starch production via cooling?

Starchy materials with a high degree of amylose result in the production of a large amount of RS3. The materials preferred include white rice, pasta, potatoes, beans, and lentils. All that needs to be done here is to thoroughly cook and then refrigerate the food for at least 12-24 hours. 

3. Is retrogradation equivalent to staling and drying?

No, they are related but different. Retrogradation relates to the desirable crystal form obtained because of cooling. Staling or drying occurs within baked products and encompasses starch retrogradation as well as dehydration, causing the product to become hard and stale. As far as health effects are concerned, we will focus on RS3, which occurs because of retrogradation in products like rice and potatoes.

Credits

This article was inspired by questions from Vivian Chung at HuffPost. 

More Food Questions America Is Asking

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🔶 Coming in Early 2026:

This topic — along with dozens of others — is explored in my upcoming book,
The Food Questions America Is Asking: How Journalists and Scientists Are Redefining What We Eat.