Here are tips on how to spend less on food:
Be brand-flexible: If you must have Heinz ketchup and will tolerate no other, that's fine. But, surely, you don't have such strong opinions about all products. Substitute a brand that's on sale or try store brands, which are much better in quality than they used to be.
Know a deal: Keep a price book, a small notepad of items you buy frequently. Unless you have a photographic memory, it's the only way to spot a good price.