Everyone loves freshly cooked, steaming-hot white rice. However, from a scientific standpoint, the starch in food undergoes a complete breakdown process: long-chain starch is first converted into short-chain starch and then further broken down into simple sugars. The starch in hot rice, being relatively easier to break down, can cause blood sugar levels to rise too quickly and increase the risk of obesity and other related health issues.

When rice is allowed to cool, the starch it contains undergoes retrogradation, which increases the amount of a substance known as “resistant starch.” Resistant starch behaves similarly to soluble fiber and is more resistant to digestion than other types of starch. It is digested slowly in the body, It has a range of effects on weight loss, blood sugar control, and more.

Therefore, it’s healthier to let the rice cool down slightly before eating it, or to reheat it first!

Note: Temperatures above 130°C will degrade resistant starch.

For a long time, starch has been widely regarded as a substance that can be completely digested and absorbed by the human body and rapidly elevate blood glucose levels. However, in 1982, researchers discovered that not all starch is digestible by enzymes; some starch cannot be hydrolyzed by enzymatic action. British biologist Englyst and his colleagues subsequently named this type of starch Enzyme-resistant starch , which is what we mentioned above as “ Resistant starch ”。

Resistant starch is A type of starch . Due to its unique chemical structure and its greater similarity to plant fibers in function, its properties Similar to “soluble fiber” , therefore it is very beneficial for the body.

① Adjunctive anti-cancer

Butyrate produced by the bacterial fermentation of resistant starch in the gastrointestinal tract can Inhibit Escherichia coli ， Reducing the Risk of Colorectal Cancer , enhance intestinal immunity and prevent intestinal diseases.

② Regulate blood sugar

Resistant starch is not absorbed by the intestine until after two hours and can also interfere with the absorption of other sugars and fats, thereby able to Helps lower blood glucose levels and improve insulin sensitivity.

③ Maintaining intestinal microbiota balance

Resistant starch is also a type of Prebiotics, It can be utilized by beneficial gut bacteria, helping to maintain intestinal microbial balance, improve the gut environment, and relieve constipation.

④ Weight loss

Resistant starch functions similarly to dietary fiber, promoting the excretion of cholesterol. It also enhances satiety, helping to control appetite and support weight loss.

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Approximately 50% of coconut oil contains Lauric acid , which can alter the structure of starch. When cooking rice, we add coconut oil, When lauric acid and the starch in rice grains undergo fusion, the resulting fused starch ultimately becomes resistant starch.

This is because lauric acid can induce the helical structure within starch molecules to solidify and become more stable, thereby preventing their conversion into blood glucose. This type of rice is more suitable for people with diabetes, as it can both lower postprandial blood glucose levels and exert anti-cancer effects.

How to Make Coconut Oil Rice

Note: For every 10°C drop in temperature, the resistant starch content in rice doubles; the cooler the rice, the higher the resistant starch content. However, water that is too cold can be harmful to the stomach; it is generally recommended to drink water at a temperature close to body temperature, around 40°C.

Resistant starch is low in energy and is widely found in Root and tuber vegetables, cereals and starchy roots, legumes, and green bananas, among others. In foods with high starch content, such as Potatoes, Chinese yam, reheated rice, beans, sweet potatoes, taro Wait—when we’re cooking, it’s best to preserve as much as possible.

Raw potatoes also contain resistant starch, but the longer they are cooked at high temperatures, the lower the resistant starch content becomes. In particular, fried potatoes and mashed potatoes contain almost no resistant starch. By contrast, stir-fried shredded potatoes have a very high resistant starch content.

Methods for Increasing Resistant Starch

Vermicelli is rich in resistant starch because it is made by processing potatoes into starch, then mixing the starch with water to form a dough, extruding it into vermicelli, and finally cooking it at high temperatures. Refrigerate and store , thereby significantly increasing the amount of resistant starch.

Resistant starch is found in certain natural foods, such as yams and sweet potatoes; in particular, high-amylose corn starch can contain as much as 60% resistant starch.

The resistant starch formed in starchy foods after refrigeration is primarily the result of the retrogradation of amylose. If a food contains a relatively substantial amount of amylose, its retrogradation upon refrigeration will be more pronounced, leading to the formation of greater amounts of resistant starch.

Conversely, if a food contains little or no amylose, it will produce very little resistant starch upon refrigeration. Short-grain glutinous rice—such as the variety used to make zongzi, tangyuan, and dage—consists almost entirely of amylopectin, and its amylopectin chains are relatively short.

A research team has conducted blood-glucose measurements and found that even after glutinous rice-based foods are refrigerated for 24 hours and then consumed, the postprandial glycemic response remains very high.

When glutinous rice is cooked and eaten hot, its glycemic index (GI) measures 112, which is already quite high. However, after refrigerating it overnight for 12 hours and then bringing it back to room temperature before eating, the GI skyrockets to 128!

So it’s best to enjoy glutinous rice dishes, like zongzi, while they’re still hot!

Although refrigeration temperatures promote the formation of resistant starch, excessive moisture still makes it difficult for the starch to become dry and hard. Foods with a moisture content of 60% or higher generally resist staling and hardening, because water molecules surround the starch molecules, preventing them from separating and causing the starch to clump together and become rigid.

Steamed buns have a moisture content of 45%–50%, making them prone to staling and hardening.

Rice typically contains about 62%–65% water; when left at room temperature, moisture evaporates, reducing the water content to below 60%, which leads to staling, drying, and hardening.

Porridge typically contains more than 85% water, and in some cases even over 90%. Therefore, even if you store porridge in the refrigerator for three days, it will not produce more resistant starch; instead, bacterial growth will only increase.

The two have vastly different effects. Refrigeration typically involves storing food at a cool temperature just above freezing for a period of time, without allowing it to freeze (refrigerator compartment); in contrast, freezing entails storing food at –18°C (freezer compartment).

The low temperatures of freezing inhibit molecular mobility, thereby preventing starch retrogradation. Reheating frozen food by steaming or boiling after thawing is essentially a second heating process, which leads to thorough gelatinization and does not increase the amount of resistant starch. In fact, if the reheating time is too long, the content of resistant starch may even decrease!

So let’s go with refrigeration after all!