The Tigers (2-0), leading 27-17 at halftime, scored 21 third-quarter points and held the Jaguars to only 15 yards total offense in the second half.
The Jaguars (0-2) scored on the game's opening possession but White combined with Antonio Gibson on a 55-yard touchdown and Keith Brown returned a blocked punt 27 yards as Memphis took a 17-7 first-quarter lead. It was the first time Memphis returned a blocked punt for a TD since 2012.
Another blocked punt led to White's 21-yard scoring throw to Gainwell and a 48-24 lead in the final minute of the third quarter. Gainwell also rushed for two scores, including a 46-yarder.
White finished 17-of-21 passing for 337 yards. Damonte Coxie had six catches for 112 yards.
Ladarius Skelton ran for 75 yards and went 7-of-15 passing for 86 yards and a touchdown pass to tight end Jeremias Houston.
Memphis outgained Southern 575-258.
Southern will be back on the grid iron September 14th when they host Edward Waters College in the Pete Richardson Classic. Kickoff is set for 6 PM. You can listen live on KQXL 106.5 with Chris Powers, Gerald Kimble and Perry White.