Who knows? This is the TSA we are talking about.

That said, I could speculate and say TSA is looking for signs of explosives on the parents, not realizing of course that if someone is intent on getting explosives on a plane in baby food, one is going to create their explosive while wearing gloves, rub down with alcohol afterwards and change one's clothes, down to one's underwear.

But as Kip Hawley once said, the TSA is only going to catch the dumb terrorist, not the smart one.