I would also point out that when you ask a blessing on over your food, it also changes the energy patterns. Is that something you could believe --or is asking for God's blessing on food just a ritual honoring Him only?
No, I don't think that prayer changes anything physical about the food. You pray more for good health and that you'll continue to have food in the first place, and even in the former situation, why not just go straight to good health? God is not restricted to energy patterns. For that matter, even if energy patterns were the mechanism for good health, God could just as easily predict your prayer in advance and prepare the food from the time it started growing. God is also not restricted to linear time.
This sort of discussion always makes my head hurt.