Rice contains two main starch components: amylose and amylopectin. When cooked with water, starch granules absorb water, swell, and undergo gelatinization. During this process, amylose tends to separate from the grains and diffuse into the surrounding water.

This "free" starch layer creates stickiness between rice grains. If a large amount of amylose escapes, the rice tends to become mushy and clump together, especially when cooked with too much water or stirred excessively.

Vinegar, primarily acetic acid, is a mild acid solution. When a small amount is added to the cooking water, the slightly acidic environment affects the starch structure in two ways:

First, it limits excessive starch swelling: The acid slows down the gelatinization process, helping rice grains maintain their shape better instead of bursting open and breaking on the surface.

Second, it reduces amylose leakage: When the outer layer of the rice grain is more stable, the amount of free starch in the water decreases, thereby limiting stickiness between grains.

As a result, cooked rice tends to be fluffier and the grains more separate than with conventional cooking methods. Additionally, the mild acidic environment slows down oxidation, helping the rice retain a brighter white color. This is why some restaurants use vinegar when cooking rice or preparing rice-based dishes.

Illustrative photo: Bui Thuy

How to use vinegar effectively when cooking rice

To achieve optimal results, add about one teaspoon of vinegar for one to two cups of rice. Incorporate the vinegar at the beginning, along with the water, before cooking. There is no need to add extra water. After the rice is cooked, open the lid to allow steam to escape, then gently fluff. In small amounts, vinegar leaves almost no sour taste; it only subtly enhances the natural sweetness of the rice.

Be careful not to use too much acid, as it can alter the taste and texture, making the rice grains slightly firm. Therefore, the amount used should be moderate.

Common mistakes that lead to sticky rice

Several common cooking habits inadvertently increase free starch, making rice stickier: Washing rice too vigorously or for too long can scratch the grain surface, releasing more starch. Stirring rice during cooking breaks down the gelatinizing grain structure. Using too much water creates a favorable environment for starch to diffuse out. In these cases, adding a little vinegar can partially rebalance the starch structure, but it cannot completely replace proper cooking techniques.

Bui Thuy