I didn't seek out an explanation, but I saw that Arthur Chrenkoff, who immigrated from Poland, talked about it in his blog, and linked to a Polish site that says:
The blessing of the Easter food, or the "Swieconka" is a tradition dear to the heart of every Pole. Being deeply religious, he is grateful to God for all His gifts of both nature and grace, and, as a token of this gratitude, has the food of his table sanctified with the hope that spring, the season of the Resurrection, will also be blessed by God's goodness and mercy.
The usual fare on the Easter table includes ham and kielbasa, cakes of all kinds - particularly babka; eggs - some shelled or some decorated. There is usually a Paschal Lamb or "Baranek" made of butter, some cheese, horseradish, salt, vinegar and oil.
The food is brought to the church and blessed by the parish priest on Holy Saturday. The food can also be blessed in the home. After the blessing, the food is usually set aside until Easter morning when the head of the house shares the blessed egg, symbol of life, with family and friends.
I guess I have to hang out around Milwaukee Avenue more often.