B737 NG Captain reported two Flight Attendants were slightly injured in cruise flight at FL320 during a wake turbulence encounter with a B747 crossing their path at FL330. Reporter stated they were not advised of the crossing traffic.

Narrative

Cruising at 32;000 feet with autopilot on in smooth air; outside of any known turbulence reports on WSI (Weather App) or from ATC or Dispatch when we experienced what seemed to be wake turbulence. It lasted for no more than one second; but was on the heavy side of moderate turbulence. I immediately put the seat belt sign on and made a PA. I then immediately called to our flight attendants and spoke with the purser to assess the condition of the cabin. She said 'everybody was fine; but there were drinks that had spilled all over the cabin'. We reported it to ATC then found out that a Boeing 747 had passed overhead by 1;000 feet; which we were not advised of. We only found out what type of aircraft when I called them back 2 minutes later to ask what had passed.The event happened roughly 52 minutes into the flight; so the FA's were in the aisle with the galley carts.30 minutes later during lav breaks the purser advised us that the two FA's in back HAD got injured (they didn't think so right away). FA A and B complained of back pain/soreness. FA C and D complained of shoulder soreness. They both had fallen and struck things with their bodies apparently. I asked if they needed medical support or paramedics to meet the aircraft and they said they did not. I immediately informed Dispatch via ACARS of the event and told him that they could continue their duties.We landed without incident; following any and all turbulence mitigation measures as we always had during this flight. I called to speak to our Dispatcher and he was not available so another dispatcher and he said he would relay for us. I then called the Chief Pilot and debriefed them.FA Supervisors were at the gate and debriefed with our Flight Attendants.