The Poskim discuss potential Kosher for Pesah issues with regard to various food items.
Bananas
Bananas are a fruit, and they clearly present no problem of Hames, per se. However, when harvested, they are extremely hot and are thrown into a liquid coolant. One might question whether the liquid contains Hames, or for that matter, whether the liquid is, in fact, Kosher for year-round use. Rabbi Blumenkrantz, in his guide to Pesah, confirms that there is no trace of Hames in that liquid. Even if there would be an issue with the Kashrut of the liquid, it would not penetrate the banana peel and affect the fruit.
Quinoa
Although it behaves like a grain, Quinoa is not a grain and is, in fact, a vegetable. It is more related to beets and spinach than to rice and millet. Therefore, its Beracha is "HaAdama," and not "Mezonot." It is also not considered Kitniyot and is permitted to Ashkenazim. Nevertheless, it does require Kosher for Pesah certification.
Mustard Seed
The Shulhan Aruch mentions preparing mustard on Pesah. Clearly, there is no issue of Hames with the mustard seed, per se. However, it is considered Kitniyot, and therefore Ashkenazim do not eat mustard on Pesah.
SUMMARY
There is no issue with regard to Bananas on Pesah.
Quinoa is neither Hames nor Kitniyot, but does require Kosher for Pesah certification.
Mustards Seed is permitted to Sepharadim, but not to Ashkenazim.
