Starch Alchemy

How your freezer and your clock change the chemistry of food

Starches are long chains of sugar molecules. 

When you eat starch, an enzyme called amylase breaks it down into sugar. That’s why starchy foods such as rice and bread can raise your blood glucose

There are ways to reduce the impact that starch has on your glucose levels. One method is simply to cool starchy foods after they’re cooked. 

This is effective because it triggers a process known as retrogradation.

Retrogradation

When starch is cooked, the molecules absorb water and expand. This makes the starchy food easily broken down by amylase in the digestive tract. The fast digestion causes fast absorption, leading to a huge spike in your blood glucose. 

If the starch is cooled after cooking, the molecules re-crystallize and become more tightly packed. 

This process is known as retrogradation and form resistant starch. 

Because its molecules are more tightly packed, resistant starch can’t be broken down by amylase. So when this type of starch hits your small intestine, it can’t be digested and absorbed, and leaves a low  impact on your blood sugar.

Foods like rice, pasta, and bread become higher in resistant starch if they’re cooled after cooking. Research has shown that cooling starchy foods doubles the amount of resistant starch that they contain.

So cooled starch has less of an impact on your blood sugar. That’s great if you like things like chilled soba noodles or onigiri. 

But what if you prefer your rice hot?

The Reheating Truth

Once starch has cooled and become resistant starch, reheating doesn’t fully reverse the process. In fact, some research has shown that cooled white rice which has been reheated contains even more resistant starch than white rice that’s still cold.

The same effect also occurs for starches in other types of food. For example, toast made from bread that has previously been frozen will contain more resistant starch than toasting from fresh. 

Gut Health Bonus

Besides its reduced impact on blood sugar, there’s another bonus to resistant starch. Because amylase can’t break it down, it passes through the small intestine and enters the colon (large intestine). There, it feeds certain beneficial bacteria.

When these bacteria process resistant starch, they produce compounds called short-chain fatty acids, such as butyrate and propionate. Over time, these compounds have been shown to improve insulin sensitivity.

So resistant starch doesn’t spike your blood sugar when you eat it, and then it gives you a compounding metabolic return by feeding beneficial bacteria.

What You Can Do Today 

The glycaemic response is the amount that your blood sugar increases after eating a particular food. Overnight refrigeration of white rice and freezing white bread before toasting reduces the glycaemic response 

This small kitchen habit produces measurable metabolic benefits, especially if you’re consistent with it over time.