We are permitted to eat chametz during the first four hours of the day before Passover. For the remainder of the day, we may eat matzah ashirah, matzah made from flour mixed with fruit juice or with eggs, which cannot be used to fulfill the obligation of eating matzah at the Seder, although many follow the practice of not eating matzah ashirah from the same hour that eating chametz becomes forbidden.
At any rate, from the beginning of the tenth hour, we may not even eat this type of matzah so that we will have a desire for the matzah that will be eaten at the Seder. One may eat fruit, vegetables, fish, or meat, provided that one does not eat an amount so large that it will prevent him from having an appetite for the matzah to be eaten at the Seder.
A person who is so delicate that if he eats during the day he will have no appetite for food in the evening, should refrain from eating during the day.
The type of matzah used for the fulfillment of the mitzvot at the Seder may not be eaten all day. However, one is permitted to feed this type of matzah to a child who is too young to understand the significance of the miracle of Passover.
Many people refrain from eating this type of matzah after the first Nissan so as to enhance the eating of the matzah at the Seder. On the day before Passover, some people refrain from eating fruit so as to enhance the eating of the charoset which is made from fruit and bitter herbs, so as to enhance the mitzvah of eating maror at the Seder. Most people, however, do not follow this custom.
Matzah which was made in the prescribed manner and then reground, mixed with fruit juice or eggs and re-baked is not considered to be matzah ashirah and may not be eaten on the day before Passover.