Final answer:
The sweetness decrease of fructose at high temperatures and its use in cold drinks can be attributed to its susceptibility to breakdown as a polyhydroxy ketone when heated. High fructose corn syrup, being rich in fructose, is stable and retains its sweetness in cold temperatures, which is why it's more suitable for cold beverages.
Step-by-step explanation:
The chemical property of fructose that could account for the decrease in sweetness at high temperatures and its use in cold drinks but not hot drinks is its structure as a polyhydroxy ketone. Heat can cause some of the chemical bonds in fructose to break down or react with other compounds, reducing its sweetness. Since fructose is the sweetest monosaccharide, its rapid breakdown at high temperatures would make it less suitable for hot drinks, as its sweetness could deteriorate during processing or consumption.
In contrast, high fructose corn syrup (HFCS), which contains a significant amount of fructose, is stable at the cooler temperatures commonly associated with cold drinks, retaining its sweetness over time. Hence, it's more commonly used in cold beverages. It's also important to note that HFCS has been involved in health discussions, with some scientists suggesting that it may play a role in the obesity crisis, although these claims are contested.