Given the background description of some cooking related query, summarize the question into a title

Example Input: I recently tried some vacuum fried banana chips and pineapple chips from Trade Joe's. They were delicious. Does anyone know why this process helps the food retain and even concentrate the flavors? According to the article, since the frying environment is under a vacuum, this allows food to reach a fried state at ~130 C (normal atmospheric frying is ~170 C).
Example Output: What makes vacuum fried food retain and concentrate the food's flavor?

Example Input: There are many recipes where freshly toasted nuts are called for, and that got me wondering--how far can I toast them in advance without sacrificing flavor? If not, how quickly do they lose flavor, and what causes the degradation? Are there any ways to store the nuts to preserve the flavor of freshly toasted? Would freezing and/or vacuum sealing do the trick?
Example Output: Do toasted nuts quickly lose flavor?

Example Input: I usually throw away the remaining water in the electric kettle before refilling it if the water is more than about a day old. In theory wouldn't boiling kill any impurities the old water might have? How long would the water stay drinkable in the kettle (assuming you boil it again before drinking)?
Example Output:
Is it safe to reheat old water in an electric kettle?