Artificial sweetener which is stable under cold conditions only is:

Aspartame is stable at cold conditions but unstable at cooking temperature.

Aspartame consists of aspartic acid, phenylalanine and methanol. It is 180-200 times sweeter than sugar. They are used in frozen desserts, gelatins, chewing gums and beverages. At high temperature, it decomposed into constituent amino acids. Thus it is referred to as a baking sweetener. Its melting point is very low. Thus is stable at very cool conditions.