1 x apple: gear 53 x 11
1 x watermelon: gear 39 x 26

Ha ha.

Seriously, for a whole lot of groceries, a trailer or a cargo bike is ideal. Look up "Xtracycle" kit, I have occasionally seen those for sale used, the most recent one was $400 on a mountain bike. For two or three bags, then two panniers and a backpack should work. I'm in the habit of stopping by the market on my commute and toting the makings of dinner home in my messenger bag. It all depends how big a shopping trip you are trying to do.