Rivkah did not mention wine, nor does the Pasuk mention it until here. What is the story behind it?
Targum Yonasan: An angel brought him wine that was kept inside its grapes (Yayin ha'Meshumar) since the creation from Gan Eden and handed it to Yaakov. 1
Malbim: He ate in order to bless him. The wine was to make it like Achilas Mizbe'ach; a libation of wine is brought with [most] Korbanos.
See Peirush Yonasan.