What is Chametz?

Chametz is almost always referred to as "leaven", "yeast" or bread that has been baked with yeast. This is partially true but it's not the whole picture. Chametz is anything made from the 5 grains (rye, wheat, spelt, oats, and barely) that has come into contact with water and begun to ferment. Our sages of blessed memory observed this process closely and concluded that this fermentation process occurs within as little as 18min after the grain has come into contact with the water*. Therefore if dough was not rolled and cooked within that time frame it would not be matzah("unleavened bread") but it would in fact be chametz dough.

This is also why all chametz isn't risen bread. Yes all breads are chametz but all chametz isn't “risen” bread. Pasta, cookies, crackers, breaded fish, pitas, grain based alcohols, etc. are just a few other things that are chametz because they have all been allowed to ferment. Pasta is fine if it is rice pasta or homemade and made within the 18min time frame....however if you have ever made pasta you'll know that could be quite challenging.

Processed and packaged foods are your "sticky wicket". Everyone needs to decide as a family or community where to place the fence line for what goes out and what can stay in.

No matter how far you go with it I believe it's a good exercise to go through and read your labels, most of us don't even know what is in half of our products, let alone whether or not they contain chametz. But this is the time to find out! You'd be surprised how many things contain these grain products or a by-product of the 5 grains. So whether you choose to remove absolutely everything or take a simpler approach remember this is a mitzvah, it's purpose is to bring us closer to HaShem! Searching both our dwelling and His(us!) for chametz is a HaShem's designed way to build our relationship with Him. Lets do it with joy and enthusiasm.

For more a more in depth article about chametz I recommend the below article written by Tim Hegg.

http://torahresource.com/EnglishArticles/Chameitz&Pesach.pdf

For me personally I first had to gain a understanding of the strictest halacha(practice), and weigh it all with Torah before coming to conclusions for my own halacha. This year that means taking anything out that has been made with one of the 5 grains(1st level meaning: in it's recognizable form, like if it says wheat flour in the ingredients) that we didn't make ourselves to insure it was not allowed to sit after water was added and become chametz. Our matzah we will make ourselves but make sure it is not able to become chametz by getting it made and baked within 18min. and washing in between batches. HaShem is gracious and gives us a little more responsibility every year! I am so thankful that He has entrusted us with guarding His Torah it is a true blessing! Shalom.

another couple I found helpful as well.

http://jerusalemcouncil.org/halacha/kashrut/chametz-not-yeast

http://www.oukosher.org/index.php/passover/article/4879/ 

http://www.oukosher.org/index.php/common/article/1380174

* note that the 18min is calculated using cold water only. If one uses hot water the fermentation begins much faster! When making matzah coldest is best!