1. The main reason is that some saponin rice has added a lot of sugar. In order to prevent it from solidifying and making it sticky to the hands, alum and glue are also added. Do not buy this kind of saponin rice again. It will last for many days. Cat stores also sell this kind of adulterated saponin rice, which does not have the SC production mark. It violates the food safety law and is illegally added.

2. If you can smell a sour and pungent sulfur gas with your nose, the sulfur dioxide residue will be quite serious. This is rare.

3. Look at its color and appearance. Generally, after sulfur fumigation, its surface will be smoother, its color will be whiter or brighter, and its shape will be better-looking.

4. If it is difficult to judge from the color, you can also take a small sip to see if it has become sour. If you have time, soak an appropriate amount in water to see if the water has a sour taste.